Dissertations / Theses on the topic 'Nano concrete'
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1
Smolikov, A. V., V. I. Pavlenko, V. M. Beresnev, D. A. Kolesnikov, and A. S. Solokcha. "Super Heavy Nano Reinforcing Concrete." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35224.
Full textAbstract:
The properties of modern heat resistant super heavy concrete reinforced by chrysotile nanotubes are
described.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35224
2
Wang, X., Q. Zheng, S. Dong, Ashraf F. Ashour, and B. Han. "Interfacial characteristics of nano-engineered concrete composites." Elsevier, 2020. http://hdl.handle.net/10454/17954.
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YesThis study investigates the interfacial characteristics between aggregates and cement paste matrix in nanofillers modified concrete. A three-point bend test on the specimens composed of two pieces of aggregates bonded with a thin layer of cement pastes with/without nanofillers was carried out to characterize the interfacial bond strength of the composites. The scanning electron microscope observations and energy dispersive x-ray spectrometry analysis were also performed to characterize the interfacial microstructures and compositions of the composites. The experimental results indicated that the nanocomposites have higher interfacial bond strength and narrower interfacial transition zone thickness as well as more optimized intrinsic compositions and microstructures than that of composites without nanofillers. Specifically, the interfacial bond strength of nanocomposites can reach 7.67 MPa, which is 3.03 MPa/65.3% higher than that of composites without nanofillers. The interfacial transition zone thickness of nanocomposites ranges from 9 μm to 12 μm, while that of composites without nanofillers is about 18 μm. The ratio of CaO to SiO2 in the interface of composites without nanofillers is 0.69, and that of nanocomposites increases to 0.75–1.12. Meanwhile, the nanofiller content in nanocomposite interface is 1.65–1.98 times more than that in the bulk matrix. The interfacial microstructures of nanocomposites are more compact and the content and crystal size of calcium hydroxide were significantly reduced compared with that of composites without nanofillers.
The National Science Foundation of China (51978127 and 51908103), and the China Postdoctoral Science Foundation (2019M651116).
3
Faghih, Faezeh. "Structural performance of nano concrete-steel sandwich wall." Thesis, City, University of London, 2018. http://openaccess.city.ac.uk/19774/.
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Concrete is extensively used in the construction of infrastructures, however formation and development of cracks undermines the integrity of the structure. Thus, both improving the mechanical properties of this construction material as well as structural health monitoring of structures are essential tasks to be tackled. The research covered in this thesis is concerned with mechanical properties of carbon nanofiber reinforced concrete and the effect of this type of concrete on structural performance of the composite steel-concrete sandwich (SC) system. The use of nanofibers such as Carbon Nanofiber (CNF) within cementitious materials is found to be effective in enhancing the mechanical properties of the cementitious material as well as enhancing the sensing ability of the cementitious composites. Despite the abundant experimental work on nanofiber reinforced cementitious composites by researchers, their use within concrete has not been fully addressed. Therefore, the significance of this research is to assess mechanical properties of nanoreinforced concrete along with its sensing capability. The steel-concrete sandwich system consists of thick concrete core with exterior steel faceplates acting as reinforcement. The steel faceplates are anchored to the concrete core with shear connectors. This study presents the structural performance of the SC element with fiber reinforced concrete (FRC) core using both single fiber and hybrid fiber (i.e. consisting of two types of fibers) in the core. For this study carbon nanofiber and steel fiber, which is conventionally used in practice, are used for the FRC. Static tests were conducted on eight SC beams with different concrete types. In addition to studying the structural performance of the SC element with fiber reinforced concrete, the self-sensing capability of beams with CNF reinforced concrete core were assessed. Furthermore, finite element analysis was conducted to evaluate the effect of some design parameters on the behaviour of SC element. The outcome of this thesis enhances the current knowledge on the use of nanofibers in civil engineering industry as nano reinforcement and nanofilaments within cementitious materials, typically concrete and it will contribute to the understanding of the effect of CNF on concrete mechanical properties. This research laid the groundwork for additional in-depth study on using carbon nanofiber reinforced concrete within structural members and determination of their effect as nanofilaments on the self-sensing capability of the structural element.
4
Wang, X., S. Dong, Ashraf F. Ashour, S. Ding, and B. Han. "Bond behaviors between nano-engineered concrete and steel bars." Elsevier, 2021. http://hdl.handle.net/10454/18564.
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YesThis paper investigated the bond characteristics between eight types of nanofillers modified reactive powder concrete (RPC) and plain steel bars, aiming to explore the modifying mechanisms and establish a bond-slip relationship model for nanofillers modified RPC and steel bar interface. The experimental results indicated that the incorporation of nanofillers can increase the bond strength and reduce the slip between RPC and plain steel bars. It was shown that a 2.15 MPa/20.5% of absolute/relative increase in cracking bond strength, a 1.25 MPa/10.3% of absolute/relative increase in ultimate bond strength, a 2.35 MPa/22.4% of absolute/relative increase in residual bond strength, a 0.592 mm/56.5% of absolute/relative reduction in ultimate bond slip, and a 1.779 mm/52.1% of absolute/relative reduction in residual bond slip were the best achieved due to the addition of various nanofillers. The enhancement of nanofillers on RPC-steel bar interface has been mainly attributed to RPC microstructure improvement, optimization of intrinsic compositions, and elimination of defects in the interface, especially the underside near steel bar, due to the nano-core effect of nanofillers enriched in the interface. In addition, the bond-slip relationship of nanofillers modified RPC-steel bar interface can be accurately described by the proposed model considering an initial branch.
The authors would like to thank the funding offered by the National Science Foundation of China (51978127 and 51908103), and the Fundamental Research Funds for the Central Universities (DUT21RC(3)039).
The full-text of this article will be released for public view at the end of the publisher embargo on 22 Jul 2022.
5
Alrumaih, Mohammed Aulwai. "Investigation of the Effect of Nano SiO2 on Porosity." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton155744355992274.
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6
El-Khoja, Amal M. N. "Mechanical, thermal and acoustic properties of rubberised concrete incorporating nano silica." Thesis, University of Bradford, 2019. http://hdl.handle.net/10454/18351.
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Very limited research studies have been conducted to examine the behaviour
of rubberised concrete (RuC) with nano silica (NS) and addressed the acoustic
benefits of rubberised concrete. The current research investigates the effect of
incorporating colloidal nano silica on the mechanical, thermal and acoustic
properties of Rubberised concrete and compares them with normal concrete
(NC).
Two sizes of rubber were used RA (0.5 – 1.5 mm) and RB (1.5 – 3 mm). Fine
aggregate was replaced with rubber at a ratio of 0%, 10%, 20% and 30% by
volume, and NS is used as partial cement replacement by 0%, 1.5% and 3%.
A constant water to cement ratio of 0.45 was used in all concrete mixes.
Various properties of rubberised concrete, including the density, water
absorption, the compressive strength, the flexural strength, splitting tensile
strength and the drying shrinkage of samples was studied as well as thermal and acoustic properties.
Experimental results of compressive strength obtained from this study together
with collected comprehensive database from different sources available in the
literature were compared to five existing models, namely Khatib and Bayomy- 99 model, Guneyisi-04 model, Khaloo-08 model, Youssf-16 model, and
Bompa-17 model. To assess the quality of predictive models, influence of
rubber content on the compressive strength is studied. An artificial neural
network (ANN) models were developed to predict compressive strength of
RuC using the same data used in the existing models. Three ANN sets namely
ANN1, ANN2 and ANN3 with different numbers of hidden layer neurons were
constructed. Comparison between the results given by the ANN2 model and
the results obtained by the five existing predicted models were presented. A
finite element approach is proposed for calculating the transmission loss of
concrete, the displacement in the solid phase and the pressure in the fluid
phase is investigated. The transmission loss of the 50mm concrete samples is
calculated via the COMSOL environment, the results from the simulation show
good agreement with the measured data.
The results showed that, using up to 20% of rubber as fine aggregate with the
addition of 3% NS can produce a higher compressive strength than the NC.
Experimental results of this research indicate that incorporating nano silica into
RuC mixes enhance sound absorption and thermal conductivity compared to
normal concrete (NC) and rubberised concrete without nano silica. This work
suggests that it is possible to design and manufacture concrete which can
provide an improvement to conventional concrete in terms of the attained
vibro-acoustic and thermal performance.Libyan Ministry of Higher Education
7
Salguero, C., C. Salguero, L. Castaneda, J. Rodríguez, and E. Carrera. "Eco-Concrete for Hydraulic Structures with Addition of Colloidal Nano-Silica." Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/651739.
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In the construction of buildings and infrastructures, high resistance materials are used due to current design requirements, concrete being one of the main materials used in the execution of these projects whose cement content is limited to obtaining an economic concrete and of minimum retraction. This limitation requires the use of new additions such as Nano Silica (NS), which due to its nanometric structure is used as a partial replacement for cement, producing an increase in strength in concrete. The present investigation studies the partial replacement of the NS in the cement to determine its behavior in compressive strength, diametric compressive strength, water permeability coefficient. The results indicate that with an addition of 0.225% of NS the compressive strength and splitting tensile strength are increased and the water permeability coefficient decreases, all of them compared to a conventional concrete.
8
Alshammari, Saleh Majed. "The Effect of Nano Silica on Porosity and Strength." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1544644895468858.
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9
Alhawat, Musab M. "Bond Performance between Corroded Steel and Recycled Aggregate Concrete Incorporating Nano Silica." Thesis, University of Bradford, 2020. http://hdl.handle.net/10454/18430.
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The current research project mainly aims to investigate the corrosion resistance and bond
performance of steel reinforced recycled aggregate concrete incorporating nano-silica under
both normal and corrosive environmental conditions. The experimental part includes testing
of 180 pull-out specimens prepared from 12 different mixtures. The main parameters studied
were the amount of recycled aggregate (RCA) (i.e. 0%, 25%, 50% and 100%), nano silica
(1.5% and 3%), steel embedment length as well as steel bar diameter (12 and 20mm).
Different levels of corrosion were electrochemically induced by applying impressed voltage
technique for 2, 5, 10 and 15 days. The experimental observations mainly focused on the
corrosion level in addition to the ultimate bond, failure modes and slips occurred.
Experimental results showed that the bond performance between un-corroded steel and
recycled aggregate concrete slightly reduced, while a significant degradation was observed
after being exposed to corrosive conditions, in comparison to normal concrete. On the other
hand, the use of nano silica (NS) showed a reasonable bond enhancement with both normal
and RCA concretes under normal conditions. However, much better influence in terms of bond
and corrosion resistance was observed under advancing levels of corrosion exposure,
reflecting the improvement in corrosion resistance. Therefore, NS was superbly effective in
recovering the poor performance in bond for RCA concretes. More efficiency was reported
with RCA concretes compared to the conventional concrete. The bond resistance slightly with
a small amount of corrosion (almost 2% weight loss), then a significant bond degradation
occurs with further corrosion.
The influence of specific surface area and amount of nano silica on the performance of concrete
with different water/binder (w/b) ratios has been also studied, using 63 different mixtures produced
with three different types of colloidal NS having various surface areas and particle sizes. The
results showed that the performance of concrete is heavily influenced by changing the surface area
of nano silica. Amongst the three used types of nano silica, NS with SSA of 250 m2
/g achieved the highest enhancement rate in terms of compressive strength, water absorption and
microstructure analysis, followed by NS with SSA of 500 m2/g, whilst NS with SSA of 51.4
m2
/g was less advantageous for all mixtures. The optimum nano silica ratio in concrete is
affected by its particle size as well as water to binder ratio.
The feasibility of the impact-echo method for identifying the corrosion was evaluated and
compared to the corrosion obtained by mass loss method. The results showed that the impact-echo testing can be effectively used to qualitatively detect the damage caused by corrosion in
reinforced concrete structures. A significant difference in the dominant frequencies response
was observed after exposure to the high and moderate levels of corrosion, whilst no clear
trend was observed at the initial stage of corrosion.
Artificial neural network models were also developed to predict bond strength for corroded/uncorroded steel bars in concrete using the main influencing parameters (i.e., concrete strength, concrete cover, bar diameter, embedment length and corrosion rate). The developed models
were able to predict the bond strength with a high level of accuracy, which was confirmed by
conducting a parametric study.Higher Education Institute in the Libyan Government MONE BROS Company in Leeds (UK) for providing recycled aggregates BASF and Akzonobel Companies for providing nano silica NS, Hanson Ltd, UK, for suppling cement
10
Abu, Bakar Asif. "Effects of Nano Silica and Basalt Fibers on Fly Ash Based Geopolymer Concrete." Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/31729.
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Emission of carbon dioxide gas has been a source of major concern for the construction industry. To curb this emission, geopolymer concrete has been deemed as a potential alternative in the recent studies. Previous research also indicates that silica and fibers provide strength benefits to ordinary Portland cement concrete OPC. This study was undertaken to recognize the benefits of adding silica and basalt fibers in Class F fly ash based geopolymer concrete and comparing it with OPC concrete. One OPC and four Geopolymer mixtures were prepared. The results show a tremendous potential of using geopolymer concrete in place of OPC concrete with Nano silica proving to be the most advantageous. Nano silica provided 28% increase in compressive strength, 8% increase in resistivity when compared with normal Fly ash based geopolymer concrete. The SEM analysis of geopolymer concrete indicates that nano silica improved the compactness of concrete providing a dense microstructure.
11
Wu, Weidong. "Multiscale modeling and simulation of concrete and its constituent materials : from nano to continuum/." Full text available from ProQuest UM Digital Dissertations, 2008. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1850457831&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1277480889&clientId=22256.
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Thesis (Ph.D.)--University of Mississippi, 2008.Typescript. Vita. "August 2008." Major professor: Ahmed Al-Ostaz Includes bibliographical references (leaves 171-184). Also available online via ProQuest to authorized users.
12
Peters, Sarah June. "Fracture Toughness Investigations of Micro and Nano Cellulose Fiber Reinforced Ultra High Performance Concrete." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/PetersSJ2009.pdf.
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Benkabou, Rim. "Étude des propriétés nano-mécaniques d’un béton." Thesis, Reims, 2018. http://www.theses.fr/2018REIMS007/document.
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Cette thèse vise à développer une méthode d'homogénéisation numérique multi-échelle pour la prédiction des propriétés élastoviscoplastiques d'un béton à haute performance (BHP), où les hétérogénéités microstructurales sont analysées par nanoindentation. La procédure d'homogénéisation a été effectuée en deux niveaux en fonction de la microstructure du BHP : le niveau correspondant à la matrice composée de produits d'hydratation, de clinker et de cendre volante, et le niveau correspondant au mortier qui contient la porosité et les agrégats. Le comportement élasto-viscoplastique des phases microstructurales individuelles de la matrice est identifié à partir des données de nanoindentation. Une méthode inverse est réalisée en utilisant la simulation par éléments finis des tests de nanoindentaion combinée à une procédure d'optimisation numérique. Les résultats micromécaniques sont ensuite utilisés comme paramètres d'entrée pour l'homogénéisation élastoviscoplastique numérique à l'échelle microscopique. Le niveau correspondant au mortier est analysé par homogénéisation numérique en utilisant la simulation par éléments finis pour prédire les propriétés globales du béton. Les résultats sont comparés aux résultats expérimentaux et analytiques macroscopiques issus de la littérature montrant un bon accord. La procéduredéveloppée dans ce travail donne des résultats prometteurs pour la prédiction des propriétés élasto-viscoplastiques du BHP et peut être étendue à d'autres lois de comportement, y compris l’endommagement. La dernière partie de la thèse est consacrée à l'étude expérimentale de deux bétons préparés avec deux adjuvants différentsThis thesis aims at developing a numerical multiscale homogenization method for prediction of elasto-viscoplastic properties of a high performance concrete (HPC) where the microstructural heterogeneities are analyzed with the nanoindentation. The homogenization procedure was separated into two-levels according to the microstructure of the HPC: the matrix level composedof hydration products, clinker and fly-ash and the mortar level which accounts for large air porosity and aggregates. The elastoviscoplastic behavior of individual microstructural phases of the matrix are identified from nanoindentation data. An inverse method is applied by using the finite element simulation of the nanoindentaion tests combined with a numerical optimizationprocedure. The micromechanical results are then used as input parameters for numerical elasto-viscoplastic homogenization at microscale. The mortar level is analyzed with numerical homogenization by using the finite element simulation to predict the overall elasto-viscoplastic high performance concrete properties. The results are compared with macroscopic experimental and analytical results from the literature showing a good agreement. The procedure developed in this work gives promising results for the prediction of HPC properties and can be extended to other constitutive laws including damage. The last part of the thesis is dedicated to the experimental study of two concretes prepared with two different adjuvants
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Rahman, Md Mahbubur. "Durability of nano-modified fly ash concrete to external sulfate attack under different environmental conditions." Canadian Society for Civil Engineering (CSCE), 2014. http://hdl.handle.net/1993/24055.
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There are still research gaps regarding the effects of key parameters such as water-to-cementitious materials ratio (w/cm), type of binder and pore structure characteristics on the response of concrete to special forms of sulfate attack: physical salt attack (PSA) and thaumasite sulfate attack (TSA). Hence, this study aims at developing an innovative type of concrete: nano-modified fly ash concrete, incorporating various dosages of nano-silica (NS) or nano-alumina (NA) and fly ash, and explores its efficiency in resisting various forms of sulfate attack.
15
Dong, S., D. Wang, Ashraf F. Ashour, B. Han, and J. Ou. "Nickel plated carbon nanotubes reinforcing concrete composites: from nano/micro structures to macro mechanical properties." Elsevier, 2020. http://hdl.handle.net/10454/18205.
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YesOwing to their small size, good wettability, uniform dispersion ability and high thermal properties, the nickel-plated carbon nanotubes (Ni-CNTs) with different aspect ratios are used to reinforce reactive powder concrete (RPC) through modifying the nano/micro- structural units of concrete. Incorporating only 0.075 vol% of Ni-CNTs (0.03 vol% of CNTs) can significantly increase mechanical properties of RPC. The enhancement effect on compressive strength caused by the incorporation of Ni-CNTs with aspect ratio of 1000 reaches 26.8%/23.0 MPa, mainly benefiting from the high polymerization C-S-H gels, low porosity, and refined pore structure. The 33.5%/1.92 MPa increases of flexural strength can be attributed to the decrease of large pore, original cracks, molar ratio of CaO to SiO2, and gel water content when Ni-CNTs with aspect ratio of 125 are added. Ni-CNTs with aspect ratio of 1500 have the largest utilization rate of being pulled-out, resulting from the improvement of dispersibility and the pining effect of nickel coating and then leading to the increased toughness. Therefore, incorporating Ni-CNTs can fundamentally modify the nano/micro- scale structural nature of RPC, providing a bottom-up approach for controlling the properties of RPC.
Funding supported from the National Science Foundation of China (51908103 and 51978127) and the China Postdoctoral Science Foundation (2019M651116).
The full-text of this article will be released for public view at the end of the publisher embargo on 7th Dec 2021.
16
Alazemi, Athbi. "Investigate the Effects of Nano Aluminum Oxide on Compressive, Flexural Strength, and Porosity of Concrete." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1544693885397299.
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Hosan, Md Anwar. "Durability Properties of High Volume Slag and Slag-Fly Ash Blended Concrete Containing Nano materials." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/83225.
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This research investigated the effect of the addition of a small amount of nano silica and nano calcium carbonate on the compressive strengths and durability properties of high volume slag (HVS) and high volume slag-fly ash (HVS-FA) blended concretes. The results showed that low-carbon concretes containing 70% blast furnace slag or 70% slag-fly blended materials with superior strengths and durability can be achievable by adding only 1% nano calcium carbonate and 2-3% nano silica.
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Dong, S., Y. Wang, Ashraf F. Ashour, B. Han, and J. Ou. "Nano/micro-structures and mechanical properties of ultra-high performance concrete incorporating graphene with different lateral sizes." Elsevier, 2020. http://hdl.handle.net/10454/17889.
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YesThe performance of cement-based materials can be controlled and tailored by adjusting the characteristics of reinforced nano inclusions. Therefore, the lateral size effect of graphene on the nano/micro-structures of ultra-high performance concrete (UHPC) was explored, and then the mechanical properties were investigated to analyze the structure–property correlation of composites in this paper. The test results show that due to nucleation site effect and the formation of core–shell elements, incorporating graphene with lateral size of > 50 µm improves the polymerization degree and mean molecule chain length of C-S-H gel by 242.6% and 56.3%, respectively. Meanwhile, the porosity and average pore volume of composites is reduced by 41.4% and 43.4%. Furthermore, graphene can effectively inhibit the initiation and propagation of cracks by crack-bridging, crack-deflection, pinning and being pulled-out effect, and the wrinkling characteristic is conductive to the enhancement of pinning effect. These improvements on nano- and micro- structures result in that the compressive strength, compressive toughness and three-point bending modulus of UHPC are increased by 43.5%, 95.7% and 39.1%, respectively, when graphene with lateral size of > 50 µm and dosage of 0.5% is added. Compared to graphene with lateral size of > 50 µm, graphene with average lateral size of 10 µm has less folds and larger effective size, then reducing the distance between core–shell elements. Hence, the addition of graphene with average lateral size of 10 µm leads to 21.1% reduction for Ca(OH)2 crystal orientation index, as well as 30.0% increase for three-point bending strength. It can be, therefore, concluded that the lateral size of graphene obviously influences the nano/micro-structures of UHPC, thus leading to the significantly different reinforcing effects of graphene on mechanical behaviors of UHPC.
The full-text of this article will be released for public view at the end of the publisher embargo on 11 Jun 2021.
19
Tang, Wei Le. "Carbonation of Concrete Incorporating High Volume of Micro and Low Volume of Nano Palm Oil Fuel Ash." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/70498.
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This research determines the carbonation resistance of concrete containing micro and nano palm oil fuel ash (POFA) using accelerate carbonation testing. Microstructures were studied using XRF, XRD and SEM. Workability and sorptivity rate were also tested. The results show that 10% micro POFA with 0.5% nano POFA had the highest carbonation resistance. Further increasing the amount of POFA would decrease the carbonation resistance of concrete.
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Campos, Neto Tiago Ferreira. "Efeitos da temperatura do concreto fresco na sua trabalhabilidade." Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/5208.
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The rheological properties...
As propriedades reológicas...
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Wan, Hassan Wan Nur Firdaus. "Mix Design Optimisation and Durability Study of High Performance Concrete Containing Micro and Nano Palm Oil Fuel Ash." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/77053.
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This study investigated the effect of micro and nano POFA as supplementary cementitious materials on the strength and durability properties of high-performance concrete. The study herein developed mathematical models to predict the workability and strengths properties of concrete containing micro and nano POFA. A numerical optimization was performed to obtain the optimal range of micro and nano POFA in the concrete mix design. Durability properties tests verified the significant effects of the optimum proposed binders in the design mix.
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Puthur, Jayapalan Amal Raj. "Properties of cement-based materials in the presence of nano and microparticle additives." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49104.
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Cement clinker production is a highly resource and energy intensive process and contributes substantially to annual global anthropogenic greenhouse gas emissions. One potential pathway to reduce the environmental footprint of cement-based materials is through the reduction of clinker content in concrete by partial replacement of cement with fillers. In this investigation, the partial replacement of cement with chemically inert nano and microsized fillers of titanium dioxide (TiO₂) and limestone was examined. The effects of nano and micro fillers on early-age properties, long-term properties, photocatalytic properties (for TiO₂-cement mixtures) and life cycle costs were measured and compared. Investigation of early-age properties shows that nanoparticles increase rate and degree of early cement hydration and chemical shrinkage due to heterogeneous nucleation effect. In contrast, coarser microparticles (>3µm in this research) maintain or marginally decrease the rate and degree of early cement hydration and decrease chemical shrinkage due to a dilution effect. In addition, temperature sensitivity of hydration reactions increases in the presence of nanoparticles. Investigation of long-term properties shows that pore size refinement is possible with the partial replacement of cement with nanoparticle fillers. But the long-term tests of filler-cement mixes also demonstrate that, compared to ordinary portland cement mix, the strength decreases and permeability increases. Analysis of photocatalytic properties of TiO₂-cement mixtures showed a lack of an appropriate testing procedure for nitrogen oxide (NOₓ) gas conversion by cement-based materials. Thus, a new standardized procedure and photocatalytic efficiency factor for characterizing photocatalytic NOₓ binding by cementitious materials is proposed. Life cycle analysis demonstrates that although inclusion of TiO₂ increases initial environmental impact of cementitious materials, the innovative photocatalytic properties of TiO₂ could improve sustainability. Life cycle analysis also shows that partial replacement of cement with limestone decreases environmental impact of cementitious mixtures due to lower processing “costs” of limestone compared to cement. Thus, the results from the current research demonstrate that variation of dosage and particle size of inert fillers can be used to tailor properties and structure of cement-based materials and that environmental sustainability can be improved by partial replacement of cement with inert fillers that introduce additional functionalities or fillers with lower embodied-energy and emissions.
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Hrout, Ghassan. "Investigate the Effect of Nano SIO2 on Porosity, Compressive and Flexural Strengths of Concrete Has 2% Fly Ash and 2% Silica Fume." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1608296326325322.
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Ahmari, Saeed. "Recycling and Reuse of Wastes as Construction Material through Geopolymerization." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/223338.
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Storage of mine tailings and waste concrete imposes economical and environmental impacts. Researchers have attempted to reuse wastes as construction material by utilizing ordinary Portland cement (OPC) to stabilize them. This method, however, has a number of limitations related to OPC. In this research, a recent technology called geopolymerization is used to stabilize mine tailings and concrete waste so that they can be completely recycled and reused. The research includes three main parts. The first part studies the effect of different factors on the mechanical properties, micro/nano structure, and elemental and phase composition of mine tailings-based geopolymer binder. The second part investigates the feasibility of producing geopolymer bricks using mine tailings. The physical and mechanical properties, micro/nano structure, durability, and environmental performance of the produced bricks are studied in a systematic way. Moreover, the enhancement of the mine tailings-based geopolymer bricks by adding cement kiln dust (CKD) is studied. The third part of the research investigates the recycling of the fines fraction of crushed waste concrete to produce binder through geopolymerization in order to completely recycle concrete waste. The results indicate the viability of geopolymerization of mine tailings by optimizing the synthesis conditions. By properly selecting these factors, mine tailings-based geopolymer bricks can be produced to meet the ASTM standard requirements and to be environmentally safe by effectively immobilizing the heavy metals in the mine tailings. The physical and mechanical properties and durability of the mine tailings-based geopolymer bricks can be further enhanced by adding a small amount of CKD. The results also show that the fines fraction of crushed waste concrete can be used together with fly ash to produce high performance geopolymer binder. Incorporation of calcium in the geopolymer structure and coexistence of the calcium products such as CSH gel and the geopolymer gel explains the enhancement of the mine tailings-based geopolymer bricks with CKD and the high performance of geopolymer binder from the waste concrete fines and fly ash. The research contributes to sustainable development by promoting complete recycling and utilization of mine tailings and concrete waste as construction material.
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Supit, Steve Wilben Macquarie. "Durability properties of high volume fly ash concretes containing nano particles." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/1756.
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This study presents the effect of nano silica (NS) and nano calcium carbonate (NC) on the compressive strength and durability properties of concretes containing high volume fly ash (HVFA). Results show that nanoparticles accelerate the hydration process and improves the microstructure of the cement and HVFA concretes for better mechanical and durability properties.
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ZIGA, CARBARIN GILDARDO JAVIER 557961, and CARBARIN GILDARDO JAVIER ZIGA. "Efecto de la introducción de nanopartículas sobre la microestructura de matrices endurecidas base cemento-portland." Tesis de maestría, Universidad Autónoma de Nuevo León, 2015. http://hdl.handle.net/20.500.11799/80201.
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Contribuciones y conclusiones: la evolución microestructural asociada por la inyección de NBS, hacia el interior de matrices cementantes en estado endurecido mejora el efecto barrera de los especímenes tratados ante el paso de agentes agresivos. Debido a que el bloqueo de poros formados por las nanopartículas disminuye el avance de la corrosión y la sortividad. Abriendo la posibilidad de que, en un futuro muy próximo, sea una posible aplicación in-situ para la prevención del deterioro prematuro de las estructuras de concreto.Propósito y método del estudio: evaluar los efectos microestructurales generadas por la inyección de nanopartículas base silicio (NBS) hacia el interior de matrices endurecidas base cemento Portland. Para este propósito se sintetizaron NBS amorfas por el método sol-gel, con tamaños menores que 25 nm. Se fabricaron morteros cilíndricos (50 mm Ø por 50 mm de largo), con un consumo de cemento (CPO-40) de 300 kg/m3 , una relación a/c de 0.65 y una relación de cemento/agregado 1:2.75, curados durante 28 días. Inmediatamente después del curado se les dio un tratamiento electrocinético, que consistió en inyectar una solución de NBS al 0.1% mediante la aplicación de un campo eléctrico de 20 VDC por 4h. Al finalizar el tratamiento, los especímenes fueron cortados transversalmente, en 3 rodajas de 50 mm Ø por 16 mm de largo y puestos en inmersión en agua, siendo monitoreados constantemente durante 60 días, mediante EIS para obtener su resistividad eléctrica, como un parámetro que se asocia con la porosidad. Se evaluaron los cambios microestructurales mediante SEM y porosimetría por fisisorción de N2. A los 45 días de haber sido aplicado el tratamiento se sometieron especímenes a ensayos de carbonatación acelerada durante 7 días y se obtuvo la absorción capilar al agua. Con la finalidad de corrobora
UNIVERSIDAD AUTÓNOMA DE NUEVO LEÓN
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Cortines, Vitor Joachim. "Estudo da inspeção e caracterização de materiais compósitos por ultrassom." Universidade do Estado do Rio de Janeiro, 2014. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=7329.
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O presente trabalho foi desenvolvido com o intuito de estudar a utilização do método de ensaio não destrutivo de ultrassom para inspecionar e caracterizar materiais compósitos. Os objetivos principais da pesquisa foram medir a espessura, encontrar e dimensionar delaminações em reparo de material compósito laminado para tubulações e medir a velocidade do som no concreto para o cálculo do módulo de elasticidade. Inicialmente foram estudados os parâmetros físicos relevantes inerentes a cada material para o método de ultrassom, para então estabelecer uma metodologia de inspeção. A técnica de pulso-eco foi capaz de encontrar as descontinuidades no compósito laminado. Para a determinação do módulo de elasticidade do concreto, a técnica de transmissão foi utilizada obtendo-se resultados satisfatórios.This work was developed with the intention of using the non-destructive testing method of ultrasound to inspect and characterize composite materials. The main objectives of the research were to find and size delaminations in laminated composite material for pipeline repair and to measure sound speed in concrete in order to determine its elastic modulus. Initially, the relevant physical parameters inherent to each material were studied regarding ultrasound so to establish a testing methodology. The pulse-eco technique was used to find discontinuities in laminated composite. To determine the elastic modulus of concrete, the through transmission technique was used with satisfactory results.
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Santos, Thyala Anarelli Cunha e. "Estudo da adição de polímero superabsorvente e de nano partículas de sílica para melhorar propriedades de concretos de alta resistência." reponame:Repositório Institucional da UnB, 2016. http://repositorio.unb.br/handle/10482/20605.
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Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2016.Submitted by Albânia Cézar de Melo (albania@bce.unb.br) on 2016-05-10T15:08:32Z No. of bitstreams: 1 2016_ThyalaAnarelliCunhaSantos.pdf: 7093670 bytes, checksum: d4a359d7b01aa424a3c75e005d32f5a6 (MD5)
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Os Concretos de Alta Resistência (CAR) proporcionaram avanços significativos na construção civil, devido à resistência superior, eficiência e durabilidade frente aos ataques do meio ambiente. No entanto, o elevado consumo de cimento, as baixas relações água/cimento e presença de adições minerais tornam necessários cuidados especiais na sua fabricação, de forma a evitar o surgimento de elevadas tensões de tração que geram retração autógena considerável e consequentemente, à fissuração dos elementos estruturais. A retração autógena é um fenômeno intimamente relacionado com a hidratação do cimento, e não depende de qualquer interferência externa. Entre as estratégias mitigadoras, a cura interna com o uso de Polímero Superabsorvente (PSA) é relatada como a mais eficiente, uma vez que proporciona água necessária à hidratação dos compostos, minimizando o surgimento de tensões nos poros capilares. No entanto, o uso de PSA aumenta a porosidade do concreto, pois deixa vazios não conectados no material endurecido, o que, reduz a resistência mecânica. Neste trabalho propõe-se o uso de nanossílica (NS) para compensar a perda de resistência mecânica causada pelo PSA. Foram desenvolvidas nove misturas contendo diferentes teores destas adições. Avaliou-se as propriedades tanto no estado fresco (como teor de ar, densidade e tempo zero pelo método do ultrassom), como no estado endurecido (resistência à compressão, à flexão e módulo de elasticidade). Também foi determinada a retração autógena, desde o tempo zero até os 28 dias. Os resultados indicam que o polímero superabsorvente é eficiente para mitigação da retração autógena, chegando a eliminá-la quase por completo no teor de 0,3%. Também se observou que a adição de NS, nos teores estudados, aumenta a resistência mecânica dos concretos (em média 15% em relação a referência). A NS, quando utilizada sozinha, aumentou a retração autógena das misturas em 10%, além de causar redução no tempo zero. Nas misturas híbridas, contendo ambas as adições, a adição de NS mostrou-se bastante promissora, uma vez que não prejudicou a ação benéfica do PSA mitigar a retração autógena, obtendo valores muito próximos ao traço contendo apenas PSA. Sua adição também compensou, quase em sua totalidade, as perdas nas propriedades mecânicas causadas pelo PSA. ________________________________________________________________________________________________ ABSTRACT
The High Strength Concretes (HSC) provided significant advances in civil construction, due its superior strength, sustainability, efficiency and durability against of environmental attacks. However, due to the high cement content, low water/cement ratio and mineral additions, a special attention is needed mostly in the production, in order to prevent the appearance of tensile stresses that may generate autogenous shrinkage and consequently the cracking of structural elements. The autogenous shrinkage is a phenomenon closely associated to the cement hydration process, and it does not depend of any external interference. Among the mitigation strategies, the internal cure using superabsorbent polymer (SAP) is reported as the most effective, whereas that it provides the necessary water for hydration of the compounds, preventing the appearance of tensile stresses in the capillary pores. However, the use of SAP increases the porosity of the concrete, because it leaves not connected voids in the hardened material, which reduces the mechanical strength. In this work was proposed the use of nanosilica (NS) to compensate the strength decrease caused by addition of SAP. Nine mixtures containing different amounts of these additions were produced. Was evaluated properties both in the fresh state (air content, density and setting time, by ultrasonic method), and in the hardened state (compressive strength, flexural strength, elastic modulus). Also autogenous shrinkage was determined, from setting zero until 28 days. The results indicate that the superabsorbent polymer is effective for the mitigation of autogenous shrinkage, reaching almost eliminate it completely with 0.3% content. It was also observed that the addition of NS in the studied content, increases the mechanical strength of the concrete (on average 15% compared to reference). The NS, when used alone, increases the autogenous shrinkage of the mixtures at 10%, and cause a reduction at time zero. In the hybrid mixtures, containing both the additions, the addition of NS seemed to be very promising, since it did not reduce the beneficial action of PSA to mitigate autogenous shrinkage, getting very close to the mixtures values containing only PSA. His addition also made up almost entirely, losses in mechanical properties caused by PSA.
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Gobi, Camila Marçal. "Estudo da influência da incorporação de Nano-Fe3O4 na reatividade de agregados em argamassas e concretos de cimento portland." reponame:Repositório Institucional da UFPR, 2017. http://hdl.handle.net/1884/47458.
Full textAbstract:
Orientador : Prof. Dr. Kleber Franke PortellaCoorientadora : Dra. Mariana D'Orey Galvão Portella Bragança
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia e Ciência dos Materiais - PIPE. Defesa: Curitiba, 22/02/2017
Inclui referências : f. 114-121
Área de concentração: Engenharia e ciência de materiais
Resumo: A reação álcali-agregado (RAA) é um mecanismo de degradação que ocorre em diversas estruturas de concreto submetidas a condições frequentes de umidade. De forma geral, trata-se de uma reação fundamentada em interações químicas entre os minerais constituintes do agregado e os álcalis presentes no cimento Portland, em presença de água. O produto formado é um gel sílico-alcalino que se expande na presença de umidade e pode impulsionar processos de fissuração nas estruturas de concreto devido ao aumento das tensões confinantes no interior dos poros do mesmo. Atualmente, já estão disponíveis várias metodologias para indicar a presença da RAA em estruturas degradadas e avaliar previamente o potencial reativo dos agregados empregados nas obras civis. Dentre os métodos de investigação mais comuns, pode-se citar por exemplo: a análise petrográfica do agregado; a microscopia eletrônica de varredura associada à espectroscopia por energia dispersiva de raios X; e o mais comum dos métodos: a avaliação da RAA envolvendo os ensaios laboratoriais normatizados pela NBR 15577 (ABNT, 2008), que permitem o diagnóstico desta manifestação patológica por meio do monitoramento da expansão de corpos-de-prova submetidos a meios agressivos. Desta forma, utilizando os métodos descritos na normativa, a intenção deste trabalho foi estudar a influência da incorporação de nano-Fe3O4 na reatividade de agregados em argamassas e concretos de cimento Portland, quando expostos a condições ambientais desfavoráveis. Além deste estudo, também foi possível verificar a relação entre a expansão experimentada pelos CP's ensaiados e a absorção de água no decorrer do ensaio, por meio do monitoramento periódico das massas das amostras; a fim de observar a expansão devido à saturação dos materiais submetidos à condição de umidade excessiva, e avaliar a sua utilização como um método de investigação da RAA. Simultaneamente a estes estudos, concretos com adição de 1% de nano-magnetita foram investigados quanto às suas propriedades físicas e mecânicas, e a conclusão obtida foi de que, com 1 ano de idade, a adição apresentou indícios de reação com o meio cimentício e diminuiu a produção de gel de RAA no interior destes; além disso, todos os resultados apresentaram parâmetros condizentes com as recomendações normativas. As conclusões obtidas nesta pesquisa evidenciaram a possibilidade de expansão do estudo da técnica de adição de nano-magnetita para concretos, que por serem ensaiados em condições de menor agressividade tendem a reagir com a adição nanométrica, mesmo que lentamente. Além disso, os dados obtidos para o monitoramento da variação mássica nos prismas, permitiram comprovar que a técnica pode ser utilizada de forma complementar a metodologia normativa de avaliação da expansão, pois, para o monitoramento ao longo de 365 dias, o ensaio de variação dimensional indicou a ausência de reação. Os produtos formados no interior dos concretos tendem, inicialmente, a acumular-se nos poros e vazios, desta forma, a expansão dos prismas pode ocorrer apenas para idades mais avançadas, muito embora já haja formação inicial de gel, identificada pela variação de massa. Palavra-Chave: Reação álcali-agregado. Manifestação patológica. Métodos de investigação. Nano-magnetita. Variação mássica.
Abstract: Alkali-aggregate reaction (AAR) is a degradation mechanism that occurs in several concrete structures subject to constant humidity conditions. In general, it is a reaction based on chemical interactions among the aggregate mineral components and alkalis contained in Portland cement, in presence of water. The formed product is a silico-alkaline gel that expands in the presence of moisture and may boost cracking processes at concrete structures due to increased confined stress inside their pores. Currently, several methods are available to diagnose the presence of AAR in degraded structures and perform a prior evaluation of the reactive potential of aggregates used in engineering works. Amongst the more common methods of investigation, some are worth mentioning, such as: aggregate petrographic analysis, scanning electron microscope associated with energy dispersive spectroscopy X-ray and the most common method: evaluation of AAR involving NBR 15577 standardized laboratory tests (ABNT, 2008), that allows the diagnosis of pathological manifestations by monitoring the expansion on samples subjected to aggressive environments. Thus, using the methods described in the normative, the primary intention was to study the influence of nano-Fe3O4 embedding in the reactivity of aggregates in Portland cement mortars and concretes when exposed to unfavorable environmental conditions. Aside from this study, it was also possible to verify the relationship between the expansion experienced by the samples tested and the water absorption during testing, by periodic monitoring of the sample masses; in order to observe the expansion due to saturation of the samples subjected to excessive moisture conditions, and evaluate its use as an additional method of AAR investigation. Simultaneously, concretes with a 1% addition of nano-magnetite were investigated as to their physical and mechanical properties, and it was concluded that, within 1 year, the addition didn't show any signs of reaction with cement and decreased the production of AAR gel on the inside of these samples; besides, all results presented parameters fitting with standardized recommendations. The conclusions obtained from this study shows the possibility of expanding the study of nano-magnetite additions techniques for concrete, which, because they are tested in less aggressive conditions, tend to react with nanometric additions, even if slowly. Furthermore, the data obtained for monitoring the mass variations in the prisms, proved that the technique can be utilized, complementarily to the standard expansion evaluation methodology, since, for the 365 days monitoring, the dimensional variance test indicated the absence of reaction. The products formed within the concrete tend at first to accumulate in the pores and voids, thus the expansion of the prisms can occur only for more advanced ages, although there are already initial gel formation, identified by mass variation. Keywords: Alkali-aggregate reaction. Pathological manifestation. Investigation methods. Nano-magnetite. Mass variation.t
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ALMEIDA, Diego Henrique de. "Adição de resíduo de louça sanitária como agregado em diferentes formulações de concreto." Universidade Federal de Alfenas, 2017. https://bdtd.unifal-mg.edu.br:8443/handle/tede/1077.
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Dentre os insumos utilizados na construção civil, o concreto é um dos mais empregados. O concreto pode ser confeccionado para fins estruturais (pontes, edifícios e demais estruturas de concreto armado ou pré-moldado) ou para fins não estruturais (calçadas, pavimentos, postes, dormentes, blocos para calçamentos, entre outros). Na confecção de concretos são utilizados o cimento (o Cimento Portland é o mais empregado), a água e os agregados, estes últimos divididos em graúdo e miúdo. Com a utilização de diversas matérias-primas a geração de resíduos é inevitável, tanto na construção civil, quanto em outros setores, tais como, as indústrias produtoras de materiais cerâmicos. Dentre os tipos de resíduos provenientes de tais indústrias, têm aqueles provenientes da produção de louças sanitárias (denominado nesta pesquisa como scrap cerâmico). De acordo com o exposto, o objetivo desta pesquisa foi estudar a adição de scrap cerâmico em substituição ao agregado graúdo em diferentes formulações de concreto. Para isso foi selecionado o resíduo de uma indústria instalada no sul do estado de Minas Gerais, e preparados concretos para determinação de propriedades físicas (slump teste, segregação e porosidade) e mecânica (resistência à compressão). Foram fabricadas cinco formulações, uma de referência (CR) e quatro com scrap cerâmico em substituição ao agregado graúdo (brita 1) nas proporções de 25% (CSC-I), 50% (CSC-II), 75% (CSC-III) e 100% (CSC-IV). No estado fresco, duas formulações não apresentaram segregação (CSC-III e CSC-IV) e duas um pequeno escorrimento de água (CSC-I e CSC-II), porém, sem comprometer a trabalhabilidade do concreto, sendo classificado, de acordo com a consistência para utilização em elementos estruturais esbeltos ou com alta densidade de armaduras. Em relação à resistência à compressão, os valores médios apresentados foram muito bons, inclusive a formulação com 100% de scrap cerâmico (fcm = 47,78 MPa). As formulações de concreto com resíduos foram classificadas como C35 e C40, de acordo com os valores de fck, sendo possível serem utilizados em estruturas. Um aspecto importante observado nos modos de ruptura dos corpos de prova; foi a pequena aderência entre o scrap cerâmico e a argamassa, devido ao esmalte no contorno do resíduo. Quanto à porosidade dos concretos, aqueles com 25%, 75% e 100% de scrap cerâmico na sua composição, apresentaram valores médios inferiores ao concreto de referência.Among the inputs used in civil construction, concrete is one of the most used. Concrete can be made for structural purposes (bridges, buildings and other structures of reinforced or precast concrete) or for non-structural purposes (sidewalks, pavements, posts, dormant, blocks for shoes, among others). In concrete manufacture, cement (Portland cement is the most used), water and aggregates (classified into coarse and fine). With the use of several raw materials the generation of waste is inevitable, both in construction and in other sectors, such as the industries producing ceramic materials. Among the types of residues coming from such industries, there are those from the production of sanitary ware (called in this research as ceramic scrap). The aim of this research was to study the addition of ceramic scrap in substitution to the coarse aggregate in different concrete formulations. For this purpose, scrap ceramic was selected in an industrial plant in the southern state of Minas Gerais, and different mixes of concrete were prepared to determine physical properties (slump test, adhesiveness and porosity) and mechanical property (compressive strength). Five formulations, one reference (CR) and four with ceramic scrap were prepared in proportions of 25% (CSC-I), 50% (CSC-II), 75% (CSC-III) and 100% (CSC-IV) in substitution of the coarse aggregate. In the fresh state, two formulations did not show adhesiveness (CSC-III and CSC-IV) and two a small water runoff (CSC-I and CSC-II), However, without compromising the workability of the concrete, being classified, according to the consistency class for use in slender structural elements or with high density of reinforcements. Regarding the compressive strength, the average values presented for all formulations were very good, including the formulation with 100% of ceramic scrap (fcm = 47.78 MPa). Concrete formulations with scrap ceramic are classified as C35 and C40, according to the values of fck, being possible to be used in structures. An important aspect observed in the rupture modes of the specimens was the small adhesion between the ceramic scrap and the mortar due to the enamel in the contour of the residue. As for the porosity of the concretes, those with 25%, 75% and 100% of ceramic scrap in their composition presented lower values than the reference concrete.
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Santos, Vito Assis Alencar dos. "Avaliação da durabilidade do concreto utilizado em postes em São Luís." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8438.
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Reinforced concrete structures built in coastal areas, such as electricity distribution poles, are constantly attacked by aggressive environmental agents. Rebar corrosion mechanism is a specific manifestation of electrochemical corrosion in an aqueous medium, thus the mechanism of corrosion of steel in concrete develops only in the presence of water or environment with high relative humidity (R.H.>60%). Chloride is known as one of the most aggressive environmental agents, causing rebar corrosion and consequent degradation of the concrete. Chlorides can reach the steel reinforcement through the pores network present in the concrete, if the device is close to marine atmosphere. The chloride content increases with time, and can attack the entire surface of the rebar, and may result in severe and dangerous corrosion velocity. Corrosion results in a decrease in rebar section and cracking of the concrete in parallel direction. The cracks occur because of corrosion products occupy more space than the original steel. In São Luis, concrete poles located on the coastal area has presented different types of pathology, mostly linked to performance of the chlorine ions. As a consequence, the life of these parts has reduced dramatically, generating maintenance costs. Therefore, this study intended to develop alternatives aimed at increasing the durability of reinforced concrete poles, by reducing the transfer of chlorides in their concrete cover, through variations in trace and concrete chemical composition, evaluating the influence of these parameters on its mechanical resistance. Therefore, many specimens were shaped with different compositions, using Type CPII E-32 Portland cement (compound slag) with water / cement ratio ranging between 0.4 and 0.5. Concrete mixtures containing silica fume (in order to reduce the capillary) and red mud additions (in order to protect the equipment by reducing the free chloride content) were also tested. Durability assessment of concrete was based on the results of its physical and mechanical characterization, on the electrical resistivity evaluation of concrete and rebar corrosion potential. Results show that silica fume and red mud addition reduces porosity and water absorption of concrete samples, as well increases mechanical strength, when compared to currently used concrete for poles manufacturing in São Luis. Additionally, it revealed a drastic reduction in rebar corrosivity when covered by concrete with these additions, tripling the life time of poles.
Estruturas de concreto armado construídas em regiões litorâneas, como postes de distribuição de energia elétrica, são, constantemente, atacadas por agentes ambientais agressivos. O mecanismo da corrosão da armadura é uma manifestação específica da corrosão eletroquímica em meio aquoso, daí o mecanismo da corrosão do aço, no concreto, só se desenvolver em presença de água ou ambiente com umidade relativa elevada (U.R. > 60%). O cloreto é conhecido como um dos mais agressivos dentre os agentes ambientais, causando, entre danos, corrosão da armadura de aço e consequente degradação do concreto. Os cloretos podem alcançar a armadura de aço através da rede de poros presente no concreto, caso o artefato esteja próximo a atmosfera marinha, tendo sua concentração aumentada em função do tempo, e pode atacar toda a superfície da armadura, podendo resultar em taxas de corrosão intensas e perigosas. A corrosão tem como consequência uma diminuição da seção de armadura e fissuração do concreto em direção paralela a esta, uma vez que os produtos da corrosão ocupam espaço maior que o aço original. Em São Luís, postes de concreto localizados na orla têm apresentado distintos tipos de patologia, em sua grande maioria ligadas a atuação dos íons cloro. Como consequencia, a vida útil destas peças tem reduzido drasticamente, gerando custos com manutenção. Por isso, o presente trabalho objetivou desenvolver alternativas visando incrementar a durabilidade de postes de concreto armado, com a redução da transferência de cloretos em seu cobrimento, variando o traço e a composição química do concreto, avaliando a influência destes parâmetros na resistência mecânica do material. Para tanto, foram moldados diversos corpos de prova (CPs), com diferentes composições, usando cimento Portland do tipo CPII-E 32 (composto com escória), com relação água/cimento variando entre 0,4 e 0,5. Traços de concreto contendo adições de sílica ativa (visando a redução da capilaridade) e de lama vermelha (no intuito de proteger a armadura pela redução do teor de cloretos livres) também foram testados. A avaliação do comportamento dos concretos se baseou em resultados de caracterização físico-mecânica do material, além da avaliação da resistividade elétrica do concreto e do potencial de corrosão da armadura. Os resultados obtidos mostram que a adição de sílica ativa e lama vermelha resultou na redução da porosidade e da absorção de água das amostras de concreto, bem como o incremento na resistência mecânica, quando comparados ao concreto utilizado atualmente na fabricação de postes em São Luís. Adicionalmente, evidenciou-se redução drástica na corrosibilidade de armaduras protegidas com concreto contendo estas adições, triplicando a vida útil das peças.
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Bragança, Mariana D' Orey Gaivão Portella. "Avaliação e monitoramento dos mecanismos de deterioração do concreto exposto ao íons cloreto e sulfato e o efeito da adição de Nano-Fe3O4 por espectroscopia de impedância eletroquímica." reponame:Repositório Institucional da UFPR, 2014. http://hdl.handle.net/1884/37257.
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Orientadora: Profª. Drª. Cláudia Eliana Bruno MarinoTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia e Ciência dos Materiais - PIPE. Defesa: Curitiba, 05/12/2014
Inclui bibliografia
Área de concentração: Engenharia e ciencia de materiais
Resumo: Determinados agentes iônicos presentes nos mais diversos ambientes (solo, água e ar) aos quais as obras de engenharia estão expostas como, por exemplo, os íons cloreto e sulfato, tendem a reagir com os hidratos do cimento, modificando as propriedades do concreto ou argamassa, levando a uma diminuição do tempo de sua vida útil. Ainda, em estruturas armadas, estes agentes influenciam na qualidade da dupla camada (concreto/barra), favorecendo o processo de corrosão da armadura, devido à interação iônica ou modificação da alcalinidade do meio. O diagnóstico desta diminuição da durabilidade normalmente envolve o desenvolvimento de ensaios laboratoriais, com a necessidade de extração de corpos de prova. Especificamente, para o concreto armado, testes envolvendo métodos eletroquímicos para a análise do potencial de corrosão e da resistência de polarização, bem como a técnica de espectroscopia de impedância eletroquímica têm sido utilizados quando da exposição a íons cloreto, devido à possibilidade de obtenção em campo da probabilidade e da taxa de corrosão em determinados pontos da estrutura. No entanto, pouco vem sendo desenvolvido acerca de outros agentes corrosivos, como os íons sulfato e, devido à complexidade do concreto, a interpretação destes resultados nem sempre é trivial. Outro desafio adveio da necessidade de interromper ou evitar estas reações químicas entre os produtos de hidratação do cimento e os diversos agentes agressivos. Técnicas envolvendo o aumento da qualidade do concreto, especificamente a permeabilidade, ainda são avaliadas como as mais promissoras. Mas, os avanços obtidos no estudo de compostos em escala nanométrica, como o dióxido de silício, têm possibilitado o desenvolvimento não só de concretos quimicamente mais resistentes, como também, de tratamento do material em estruturas susceptíveis ou em fase inicial de degradação. Assim, o presente trabalho visou o desenvolvimento de estudo eletroquímico de causa e efeito dos mecanismos de deterioração do concreto exposto aos íons cloreto e sulfato, com possível modificação das propriedades devido a adição de 1% (massa%/massa de cimento) de nano-Fe3O4 na dosagem padrão. Para tal, óxidos nanométricos, dentre os quais óxidos de silício, ferro, titânio e alumínio foram caracterizados e analisados quanto ao desempenho físico-químico em dosagens de concreto, tanto do ponto de vista mecânico, quanto e principalmente frente à durabilidade relativa a um padrão de referência, em condições de envelhecimento laboratorial em meio contendo íons agressivos. Os resultados obtidos evidenciaram a possibilidade de utilização da técnica de espectroscopia de impedância eletroquímica para o acompanhamento da diminuição desta durabilidade relativa do concreto sujeito à exposição aos íons cloreto e sulfato, sendo possível a detecção dos processos de corrosão em estágios iniciais de degradação. Ainda, foi verificada a melhora das propriedades mecânicas e físicoquímicas do material com a adição de 1% (massa%/massa de cimento) de óxidos nanométricos, com destaque para o nano-Fe3O4, possibilitando o desenvolvimento de materiais de maior durabilidade. Palavras-Chave: Concreto armado. Íons cloreto e sulfato. Durabilidade. Espectroscopia de Impedância Eletroquímica. Nano-Fe3O4.
Abstract: The buildings can be exposed to ionic agents present in environment (soil, water and air), such as chloride and sulfate, which ones tend to react with the cement hydrates and could modify the concrete or mortar properties, dropping the materials lifetime. Especially in reinforced structures, these agents influence the double layer (concrete/bar) quality, promoting the bar corrosion due the ionic interaction or the modification of the environment alkalinity. The diagnosis of this durability reduction involves laboratory tests and the specimens' extraction is normally necessary. Specifically for reinforced concrete there are some electrochemical tests, such as the corrosion potential, the polarization resistance and the electrochemical impedance spectroscopy that have been widely used to study the chloride ions exposition, because of the possibility of obtaining, even in the field, the corrosion probability and rate of some points in the structure. However, there is little research developed about electrochemical tests to study the exposition to other corrosive agents, such as sulfate ions. Furthermore, because of the concrete complexity, the results interpretation is not trivial. Another challenge is the necessity of stopping or avoiding these chemical reactions between the products of cement hydration and the aggressive agents. Currently, the most promising techniques involve the enhancement of concrete quality, especially from the permeability. Although, there are some advances in the nanoscale compounds studies, which have raised the development of more chemically resistant concretes and also special treatments for the material presented on structures in early stages of degradation. The present thesis aimed the development of a cause and effect electrochemical study of distress mechanisms in concrete with and without additions of nano-Fe3O4 in partial cement replacement, used to enhance the material's durability. For that, nanoscale ceramic oxides, such as silicon, titanium, iron and aluminum oxides were characterized and added in concrete dosages, as partial replacement of cement. The obtained material was analyzed for physical and chemical measurements, to evaluate the structural performance and the durability characteristics under laboratory aggressive ions exposition. The obtained results confirmed the electrochemical impedance spectroscopy as an ideal technique for monitoring the durability drop of concrete subject to sulfate and chloride ions exposition and with that it was possible to detect the corrosion and deterioration in early stages. In addition, there was developed a new concrete, with better mechanical and physicochemical properties by the addition of 1% nano-Fe3O4, enabling the dosage of more durable concretes. Keywords: Reinforced concrete. Chloride and sulphate ions. Durability. Electrochemical impedance spectroscopy . Nano-Fe3O4.
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PINHO, José Rodrigo Santana. "Avaliação de sistemas de reparo para o problema de abrasão do concreto de superfícies úmidas em usinas hidrelétricas." Universidade Federal do Pará, 2006. http://www.repositorio.ufpa.br:8080/jspui/handle/2011/1881.
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REDE CELPA - Centrais Elétricas do Pará
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The research field of construction pathology has been steadily growing lately due to natural degradation observed in different structures. In this sense, great attention has been devoted to special concrete structures such as hydroelectric power plants (HPP) because of their complexity and importance, socially as well as economically. One of the pathologies that is most found in these structures is hydraulic abrasion of concrete, which can lead, in extreme cases, structures to complete failure. The objective of this research work is to obtain and analyze test data of various repair materials regarding their resistance to hydraulic abrasion as well as their respective adherence systems. The research was divided into three phases: the purpose of the first phase was to investigate the physical and mechanical characteristics of the repair materials; the objective of the second phase was to analyze the compatibility between the repair material and the substrate through the evaluation of adherence by the slant shear test; Finally, the purpose of the third phase was to provide data about the abrasion resistance of the repair materials through the ASTM C1138 testing method. In the first phase, axial compression tests and consistence tests were perfomed with the concretes and mortars used as deep and superficial repairs at 3, 7 and 28 days. In the second phase, adherence tests were made, at 3 and 28 days, in the adhesive systems, which consisted of polymers and cement based materials. In the last phase, the same repair materials of the first phase were used: cement based mortars and concretes with and without pozolanic addition silica fume and high reactive metakaolin and an epoxy mortar at 3 and 28 days of age. As results, axial compression strengths between 40 to 65 MPa were obtained for the cementitious materials at 3 days of age and between 60 to 80 MPa at 28 days. Meanwhile the epoxy mortars strength was 20 MPa for both ages. The mortars consistency was thixotropic, while the concretes ones were very fluid. Regarding the adherence tests, the surfaces were first scarified, then clean and wet, which provided a condition for the cementitious adhesives to perform much better than the polymeric ones, even for those that were recommended for adhesion in wet substrates. In the abrasion test phase, a new methodology was used to prepare the concrete substrates before the application of the repair materials. The repair that achieved the best results under abrasion was the epoxy mortar. No statistically significant difference was observed between the concretes with and without pozzolanic additions. In general, the mortars wear, especially at 3 days, was larger than the concretes wear, in which the presence of two stages of rate of degradation were clearly verified, due to the abrasion resistance of the coarse aggregates. Therefore, it was possible to identify different stages of abrasion wear for the tested concretes.
A área de pesquisa em patologia das construções vem crescendo muito ultimamente, devido à degradação natural observada nos mais diversos tipos de edificações. Neste sentido, grande atenção vem sendo dispendida às estruturas de concreto de obras especiais como usinas hidrelétricas (UHEs) em virtude de sua complexidade e importância, tanto social quanto econômica. Uma das patologias que mais ocorrem nestas estruturas é a abrasão hidráulica do concreto, a qual pode levar a construção à ruína, em casos extremos. Este trabalho visa obter e analisar dados de vários materiais de reparo quanto à resistência à abrasão hidráulica e quanto aos seus respectivos sistemas de aderência. Dividiu-se a pesquisa em três grandes etapas: na primeira verificaria as características físicas e mecânicas dos materiais de reparo, a segunda analisaria a compatibilidade entre reparo e substrato através da aderência obtida no ensaio de compressão na junta diagonal e a terceira forneceria dados sobre a resistência à abrasão dos reparos através do ensaio ASTM C1138. Na primeira etapa foram realizados os ensaios de resistência à compressão axial e consistência dos concretos e argamassas utilizados como reparos profundos e superficiais para as idades de 3, 7 e 28 dias; Na segunda, aos 3 e 28 dias de idade, foram realizados os ensaios de aderência dos sistemas adesivos, abrangendo materiais cimentícios e à base de polímeros; Na última etapa foram utilizados os mesmos materiais de reparo da primeira: argamassas e concretos à base de cimento com e sem adição de pozolanas sílica ativa e metacaulim e argamassa à base de resina epóxi aos 3 e 28 dias. Como resultados, foram obtidas resistências à compressão axial entre 40 e 65 MPa para os materiais cimentícios aos 3 dias de idade e entre 60 e 80 MPa aos 28 dias, enquanto que para a argamassa epóxi a resistência foi de 20 MPa para ambas as idades. A consistência das argamassas foi tixotrópica, enquanto que a dos concretos foi bastante fluida. Quanto à aderência, realizou-se a aplicação dos adesivos em superfícies escarificadas, limpas e encharcadas, o que possibilitou uma expressiva vantagem dos adesivos à base de cimento e relação aos poliméricos, mesmo estes sendo indicados para colagem em substratos úmidos. Na etapa de abrasão dos reparos, utilizou-se uma nova metodologia de preparo dos substratos de concreto e posterior aplicação dos reparos, classificados em profundos ou superficiais. O reparo que apresentou maior resistência à abrasão foi o de argamassa epóxi. Não houve diferença estatística significativa entre os concretos sem adição e com adição de sílica ativa e metacaulim de alta reatividade. Em geral, o desgaste das argamassas, especialmente aos 3 dias, foi maior que o dos concretos, onde se verificou claramente a presença de dois estágios de taxa de desgaste em função da resistência à abrasão dos agregados graúdos. Assim, foi possível identificar diferentes estágios de desgaste para os concretos utilizados.
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MORAES, Ruan Fabrício Gonçalves. "Avaliação da durabilidade de concretos produzidos com agregado miúdo reciclado de cerâmica vermelha." Universidade Federal do Pará, 2016. http://repositorio.ufpa.br/jspui/handle/2011/9879.
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A geração de resíduos de construção civil (RCC), no Brasil e no mundo são de grandes proporções. Porém, o seu reaproveitamento não se dá na mesma medida em que são gerados pela construção civil, soma-se a isso, a necessidade de encontrar soluções para o depósito em aterros destes resíduos, a insustentabilidade do consumo de recursos naturais, onde jazidas já apresentam sinais de escassez de agregados. Logo, a utilização da cerâmica vermelha como agregado para concreto traz consigo a consciência de cooperação ambiental e sustentabilidade. Neste cenário, onde a bibliografia ainda se encontra escassa com relação às propriedades de durabilidade do concreto com este tipo de agregado, este trabalho teve como objetivo melhorar e difundir o conhecimento a respeito deste resíduo na construção civil. Para isso, foram produzidas misturas com relação água/cimento de 0.45; 0.55 e 0.65, onde, o agregado miúdo natural foi substituído pelo agregado miúdo cerâmico em 0%, 12,5% e 25%, e cada porcentagem foi submetida às taxas de pré-molhagem de 40%, 60% e 80%. Posteriormente, foi avaliada a durabilidade dos concretos produzidos com agregado miúdo cerâmico (AMC), através de ensaios de absorção por capilaridade, carbonatação, resistividade elétrica e penetração de íons cloretos. Com os resultados obtidos, pode-se concluir que o abatimento foi satisfatório na maioria das misturas, e em relação à durabilidade, de modo geral, todas as misturas com agregado reciclado cerâmico apresentaram maior durabilidade que as de referência, principalmente nas misturas com 25% AMC. As taxas de pré-molhagem mostraram-se eficientes na maioria das misturas, mostrando satisfatória influência nos resultados finais em todos os ensaios realizados. Portanto, conseguiu-se mostrar grande viabilidade da utilização deste resíduo no concreto, melhorando o seu desempenho.
The generation of waste from civil construction (WCC) in Brazil and in the world are of great proportions. However, its reuse does not occur in the same proportions that are generated by construction, is added to this, the need to find solutions for the landfilling of these wastes, unsustainable consumption of natural resources, where deposits already present signals aggregate shortage. Therefore, the use of red ceramic as recycled aggregate, reduces costs for the production of concrete, brings awareness of environmental cooperation and sustainability. In this scenario, the literature is still scarce in relation to the concrete durability properties for this kind of aggregate. Thus, this study aimed to improve and disseminate knowledge about these waste in construction. To this end, mixtures were made with water / cement ratio of 0.45; 0.55 and 0.65, where the aggregate has been replaced by natural fine ceramic aggregate in 0%, 12.5% and 25%, each percentage was subjected to pre-wetting rate of 40%, 60% and 80%. Subsequently, the durability of concrete produced with fine ceramic aggregate (FCA) was evaluated through capillary absorption, carbonation, electrical resistivity and chloride ion penetration. With the results obtained it can be concluded that the slump test was satisfactory in most mixtures, with respect to durability, in general, all mixtures with ceramic recycled aggregate had higher durability than the reference, especially in mixtures with 25% AMC. Pre-wetting rates were effective in most mixtures, showing satisfactory influence on the final results in all tests. So it managed to show great feasibility of using this waste in concrete, improving their performance.
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Paiva, Antônio Ernandes Macêdo. "Desenvolvimento de um equipamento para avaliar propriedades elásticas de cerâmicas refratárias a altas temperaturas pelo método de ressonância de barras." Universidade Federal de São Carlos, 2002. https://repositorio.ufscar.br/handle/ufscar/746.
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Previous issue date: 2002-09-12Financiadora de Estudos e Projetos
The knowledge of the elastic properties has been of fundamental importance for the understanding of the limitation of the useful life of structural refractory ceramics. Those properties characterize the elastic rigidity of the materials and represent a requirement for the specific classification of the materials and their mechanical characteristics. The determination of properties, such as, Young s modulus (E), shear modulus (G) and Poisson s ratio (µ) are important for the determination of several important mechanical properties. In this work the dynamic method of bar resonance was used to obtain those three elastics properties. It consists in the stimulation of a sample with variable frequency, in order to obtain the fundamental frequency and their harmonics of natural vibration of the body. Considering the density and the geometry of the sample the elastic properties of the material are obtained. Therefore, the objective of this work was to develop an automatic equipment to measure E, G and µ as a function of the temperature using the technique of bar resonance and a software that controls the system. As exemplification of the use of that software and of that equipment, a study of the influence of the aggregate s size (DL = 2800, 4750 and 8000 µm) and of the Andreasen s coefficient of particle size distribution (q = 0,21; 0,26 and 0,31) on the thermal shock damage in alumina refractory castables was accomplished. Besides, other study about the influence of the porosity on the elastic properties of cellular ceramics processed by gelcasting was also carried out. The dependence of E and G on the porosity according to models found in the literature was confirmed. The dependence of the elastic moduli on the temperature of for those foams was also evaluated.
0 conhecimento das propriedades elásticas tem sido de fundamental importância para o entendimento da limitação da vida útil de cerâmicas refratárias com fins estruturais. Essas propriedades caracterizam a rigidez elástica dos materiais e representam, em primeiro lugar, um pressuposto para a classificação específica dos materiais e suas características mecânicas. A determinação de propriedades, tais como, módulo de Young, E, módulo de cisalhamento, G, e razão de Poisson, µ, são importantes na determinação de várias outras importantes propriedades mecânicas. Neste trabalho utilizou-se o método dinâmico de ressonância de barras para a obtenção dessas três propriedades elásticas, que consiste no estímulo de um corpo de prova com freqüência variável, a fim de se obter a freqüência fundamental e seus harmônicos de vibração natural do corpo. Dessa freqüência, considerando ainda a densidade e a geometria do corpo de prova, obtêm-se as propriedades elásticas do material. Portanto, o objetivo deste trabalho foi desenvolver um equipamento automático para medir E, G e µ em função da temperatura, utilizando a técnica de ressonância de barras e um software de controle e análise dos resultados. Como exemplificação do uso do software e deste equipamento, um estudo da influência do tamanho de agregado (DL = 2800, 4750 e 8000 µm) e do coeficiente de distribuição de Andreasen de tamanho de partículas (q = 0,21, 0,26 e 0,31) sobre o dano causado por choque térmico em concretos refratários aluminosos foi realizado. Além disso, foi realizado outro estudo sobre a influência da porosidade nas propriedades elásticas de cerâmicas celulares processadas por gelcasting. A dependência de E e G com a porosidade segundo modelos encontrados na literatura foi confirmada. Avaliou-se também o comportamento dos módulos elásticos em função da temperatura nestas esponjas.
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Alhawat, Musab, Ashraf F. Ashour, and Amal El-Khoja. "Properties of concrete incorporating different nano silica particles." 2019. http://hdl.handle.net/10454/17071.
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YesThis paper aims to evaluate the influence of surface area and amount of nano silica (NS) on the performance of concrete with different water/binder (w/b) ratios. For this purpose, 63 different mixes were produced using three NS having three differentsurface areas (52, 250 and 500 m2/g) and w/b ratios (0.4, 0.5 and 0.6). Compressive strengths , workability, water absorption and the microstrcture of concrete mixtures were measured and analysed. and the optimum ratio for each type was determined. The results indicated that the performance of NS particles in concrete is significantly dependent on its amount and surface area as well as w/b ratio. As the w/b ratio increased, a better performance was observed for all types of NS used, whilst NS having 250m2/g surface area was found to be the most effective. The optimum amount of NS ranged from 2 to 5%, depending on NS surface area.
The full-text of this article will be released for public view at the end of the publisher embargo on 15 May 2020.
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Lin, Hsiu-Chen, and 林綉禎. "Application of Nano Photocatalyst Porous Concrete on Air Purification." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/up2452.
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碩士國立臺灣科技大學
營建工程系
95
The environmental purify has become the most important issue among all the countries. The nano-photocatalyst has the ability to improve the environmental problem such as air pollution. At present, due to no side effect occur the nano-photocatalyst has widely applied to air purification. The study focus on application of Photocatalyst combines with the porous concrete as outdoor air purification material to solve the air pollution problem of Taiwan. To evaluate the photocatalysts reaction under conditions of low humidity and room temperature, the three variables, air voids of porous concrete, intensity of UV light, and factor of SiO2, were considered. Moreover, the reversion efficiency was investigated by perform the water clean method. The test results show that amount of adsorption of NO2 is affected by box wall and porous concrete. Thus, the degradation speed of initial stage is faster then later stage. As expected, the high intensity UV light result in a high photocatalysts reaction. The test result shows that before water clean the porous concrete has faster degradation speed than after water clean one. However, the reversion efficiency for each test groups has upward to 80%. Furthermore, the porous concrete that surface treating by SiO2 and then coating nano-photocatalyst has high degradation performance. Therefore, the middle layer as SiO2 can helps the long term durability. The nano-photocatalyst of situations of film formation and adhesion is affected by the air voids of porous concrete, and result in different photocatalysts reaction. Based on test results indicating the air voids of porous concrete at 15% and 20% have excellent ability of air purification. In according the statistical analysis show that 20% air voids was recommended to be the appropriate air voids contend.
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Yuan, Yu-Shiang, and 游翔淵. "A Study on the Thermal Effects on Glass Fiber Reinforced Concrete and Nano Clay Concrete." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/tf9335.
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碩士中原大學
土木工程研究所
93
ABSTRACT In this research, glass fiber is added to the concrete in order to improve the fragility of the ordinary concrete. Throughout the research, percentage of glass fiber is measured by weight instead of volume. The percentage of glass fiber by weight in this research has three different contents: 0.5%, 1.0% and 1.5%. Experiments show that a 1.0% fiber content produce best results: an increase of 13.6% in compressive strength, 22.44% in flexural strength and 25.81% in of split tensile strength. The resistance against high temperature of glass fiber is examined with SEM analysis. The thermal conductivity of the fiber reinforced concrete is also decreased. In this research, nano-clay is also added to the concrete with an amount of 0.1%, 0.3% and 0.5% by weight. Due to its nano grain size, voids among the C-S-H can be filled by nano-clay, thus increase the density of the concrete. Hydration degree of concrete is increased due to presence of nano-clay as shown by Loss of Ignition Tests. In the XRD tests, results show that nano-clay reduced the wave peak of calcium hydroxide. This can prove that nano-clay improves pozzolanic reactions. In aspect of strength of nano-clay concrete, a 0.3% of nano-clay produces a 16.18% increase in compressive strength, and 41.99% increase in split tensile strength. Nano-clay can fill the voids among C-S-H and makes the concrete denser.
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Lin, Jiun-hung, and 林俊宏. "The fracture toughness enhancement of concrete specimens by adding nano-silica." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/46674338522539235637.
Full textAbstract:
碩士逢甲大學
土木工程所
98
Nano technology is the chemical, physical, mechanical, materials, electronics, measurement and other technology integration, and growing development of nanotechnology, applications are increasingly wide range. Civil construction engineering in the most widely used material shall be concrete, concrete quality is good or bad will have a direct impact on the safety of structures, therefore, how to enhance the strength of concrete as in recent years, scholars and experts to pursue national objectives. Nano silica is a new add material, replacing the traditional silicon powder for the pollution and harm the human body, generally used for coating reinforcement, but the experiment that has added to enhance the strength of concrete results. This article studies how the different amounts of replacement of cement, to investigate the effect of nano-silica powder on the concrete strength. In this study, the first in the percentage of cement mortar adding different nano-silica powder, proper age of conservation, the compressive strength were tested, of which 0.6% of cement replaced by the largest amount of results generated. Then reveals that the best addition of nano-silica powder added to the concrete were measured compressive strength and fracture toughness of the upgrade amount. Fracture mechanics is to research the material crack tip stress - strain relations theory that the method of fracture toughness. Previous researches on the mechanics of concrete, and more stress on the compressive strength and elastic modulus, fracture toughness of concrete rare, this research in a different amount of silica powder added to observe the enhancement of fracture toughness of concrete results, experiments results indicated that replacement of cement with 0.6% of the amount of enhancement of fracture toughness of the concrete effects of the most remarkable Key word: nano-silica, Fracture Mechanics, Fracture toughness enhancement
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Chung, Co-Chia, and 鐘和家. "Microstructure and Physcial Properties of Concrete paste Prepared by a Nano-technology." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/77821469263789479941.
Full textAbstract:
碩士國立高雄應用科技大學
化學工程系碩士班
92
Microstructures and compressive strength of concrete and superplasticizing concrete pastes prepared by nano-technology were investigated by scanning electron microscope (SEM) and universal compressive tester. In Part A, an inorganic cluster of polysilsesquioxane (POSS) in nano-scale was prepared by sol-gel method and was subsequently added into cement pastes. POSS was formed via the hydrolysis and the condensation reaction of methyltrimethoxysilane (TMOS) or /and 3-glycidoxypropyltrimethoxysilane (GPOS) with polyethylenimine linear (PEI) and identified by the fourier transformation infra-red (FTIR) spectrum. In-situ developing microstructure and compressive strength of various cement pastes with different level of POSS (1, 3, 5 and 10 phr based on weight of cement) were monitored and tested at the different curing time. The densification effect is not apparently observed when POSS content is less than 5 phr in the concrete paste. Whereas, the densification effect is gradually promoted to a plateau level when POSS content reaches 10 phr in the concrete paste. Microstructures of superplasticizing concrete paste with inorganic clusters of POSS are densification because of superplasticizer. The POSS content in concrete or superplasticizing concrete pastes is less than 3 phr, the compressive strength of early period is low strength, but the compressive strength of later period increases progressively. The absorption capacity and permeability of concrete or superplasticizing concrete pastes decreased with the content of POSS increased. In Part B, montmorillonite clay was modified by the cetylpyridinium chloride (CPC) and was subsequently added into cement pastes. The organoclay (MMT-C) is identified that the interlayer spacing is increase from 1.41 nm to 1.98 nm by X-ray Diffractometer (XRD). In-situ developing microstructure and compressive strength of various cement pastes with different level of MMT-C (1, 5 and 10 phr based on weight of cement) were monitored and tested at the different curing time. The densification effect is obviously observed when MMT-C content reaches 10 phr in the concrete paste. Microstructures of superplasticizing concrete paste with MMT-C are densification because of superplasticizer. The compressive strength of concrete paste with MMT-C is high strength when MMT-C content is 1 phr. The compressive strength of superplasticizing concrete paste with MMT-C decreases progressively with the content of MMT-C increased. The absorption capacity and permeability of concrete or superplasticizing concrete pastes decreased with the increasing amount of MMT-C.
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Alhawat, Musab, and Ashraf F. Ashour. "Bond strength between corroded steel and recycled aggregate concrete incorporating nano silica." 2019. http://hdl.handle.net/10454/17507.
Full textAbstract:
YesLimited information related to the application of nano silica in recycled aggregate concretes has been available in the literature. However, investigations on the effect of nano silica on the bond performance of reinforcement embedment length in recycled aggregate concrete have not been conducted yet. Therefore, the present study aimed at investigating the bond strength for recycled aggregate concretes incorporating nano silica under different levels of corrosive environments. The experimental work consisted of testing 180 pull-out specimens prepared from different mixtures. The main parameters studied were the amount of recycled aggregate (i.e. 0%, 25%, 50% and 100%), nano silica (1.5% and 3%), embedment length (5 and 13Ø) as well as reinforcement diameter (12 and 20mm). Different levels of corrosion were electrochemically induced by applying impressed voltage technique for 2, 5, 10 and 15 days. Finally, the experimental results were compared with the existing models. Experimental results showed that the bond performance between un-corroded steel and RCA concrete slightly reduced, while a significant degradation was observed after being exposed to corrosive conditions, in comparison to normal concrete. On the other hand, the use of a small quantity of NS (1.5%) showed between 8 and 21% bond enhancement with both normal and RCA concretes under normal conditions. However, much better influence was observed with the increase of corrosion periods, reflecting the improvement in corrosion resistance. NS particles showed a more effective role with RCA concretes rather than conventional concretes in terms of enhancing bond and corrosion resistance. Therefore, it was superbly effective in recovering the poor performance in bond for RCA concretes. By doubling the content of NS (3%), the bond resistance slightly enhanced for non-corroded samples, while its influence becomes more pronounced with increasing RCA content as well as exposure time to corrosion.
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-Chieh, Li, and 鄭力介. "Effect of Engineering Properties on High Performance Concrete with Nano-precipitated Calcium Carbonate." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/97528642038132251352.
Full textAbstract:
碩士國立雲林科技大學
營建工程系碩士班
101
As construction projects, it is gradually lack of concrete materials due to over-mining of resources, renew technology or alternative materials for the construction material of sustainable development. The development of nano-materials is now the world''s trend in the field of nanotechnology, many material properties will change, and such a method for producing nano-precipitated calcium carbide of traditional manufacturing, it does not make CO2 increased in emissions polluting the environment. This research focuses on adding nano-precipitated calcium carbonate in cement mortar and nano-precipitated calcium carbonate and pozzolan (fly ash, slag) replacement of cement in concrete. The test items include slump and slump flow test, L-shaped groove filling length test, V-type through the time trial, the compressive strength in High Performance Concrete. Test results showed that adding nano-precipitated calcium carbonate can improve the workability of concrete, and the workability is better with nano-precipitated calcium carbonate to add 3%; adding nano-precipitated calcium carbonate can improve compressive strength of concrete, but decrease in compressive strength with more than 3%. With fly ash 5% replacement of cement, the compressive strength is better to add nano-precipitated calcium carbonate 1% to 3%, but with slag 5% replacement of cement, the compressive strength decreased with nano-precipitated calcium carbonate.
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Hsu, Chang-Tse, and 徐彰澤. "Study on Engineering Properties of Concrete with Additions of Nano Powder and Polymer." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/22278288971856012364.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
101
The research mainly focuses on the investigation of the enhancement of engineering properties of polymer concrete with additions of nano modified clay (NMC) and nano silica fume (NSF). The variables of concrete mixtures, with fixed values of water-to-binder ratio (W/B = 0.4), percentage of sand (S/A = 40 % volume of aggregate), polypropylene fiber (PP = 0.2 % volume of concrete) and micro silica fume (MSF = 10 % volumetric replacement of cement), water based acrylic resin (P/B = 5 % weight of cementitious powder), include the amount of nano silica fume (NSF = 0, 0.05, 0.1 % replacement of cement by weight), and the amount of nano modified clay/acrylic resin (NMC = 0, 5, 10% replacement of resin by weight), which were used to study the influence on the engineering properties, durability and abrasion resistance of polymer concrete. The results of study show that：(1)Engineering properties：At age of 56 days, after adding NSF, except for the compressive strength increased by 3 % and the water absorption decreased by 3.7 %, all the other engineering properties of concrete are slightly decreased by less than 5 %. On the other hand, after adding NMC, except for the splitting tensile strength increased by 4.9-6.1 %, all the other engineering properties of concrete are slightly decreased by less than 12 %.(2)Durability properties：At age of 14 days, both nano materials can increase the value of surface resistivity by 43.8 % and 5.5 % for concrete with NSF and NMC, respectively. , and, at age of 56 days, reduce the value of rapid chloride permeability by 23.9 % and 16.4 % for concrete with NSF and NMC, respectively. (3)Abrasion resistance properties：The additions of NSF and NMC can reduce the amounts of abrasion by 21.5 % and 10.5 % at dry condition, by 16.8 % and 15.8 % at wet condition, respectively. From above-mentioned results, an appropriate addition of either nano material can significantly increase the resistance of rapid chloride permeability and abrasion of polymer concrete with the sacrifice of slight decreases of other engineering properties like compressive strengths and elastic properties.
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Jing-Wen, Huang, and 黃敬文. "Studies on the Engineering Properties of High Performance Concrete Containing Nano-silica Powder." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/78240974096072894636.
Full textAbstract:
碩士國立高雄應用科技大學
土木工程與防災科技研究所
92
The purpose of the study is to investigate the engineering properties of High Performance Concrete (HPC) contain Nano-silica Powder. The specimen of this study was made with Water-binder ratio (W/B=0.24, 0.28 and 0.32) and the varying content of Nano-Silica powder (1.2%, 1.8% and 2.4%) to study the strength properties of the High Performance Concrete, durability, microstructure properties. The test included compression strength, splitting strength, dynamic modulus of elasticity, chloride ion penetration test, corrosion rate, ultrasonic wave propagation velocity measurement, Field emission scanning electron microscope (FE-SEM), and X-Ray diffraction (XRD). The result shows that adding Nano-Silica Powder in concrete will make the mechanical properties, low permeability and high electrical resistivity, and the densification effect by Nanoparticles into cement pastes is obviously promotes with indicated that Nano-Silica Powder had consumed Calcium Hydroxide the in pozzolanic reaction by FE-SEM and XRD.
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Su, Yu. "Advances in development of novel ultra-high performance concrete." Thesis, 2017. http://hdl.handle.net/2440/112039.
Full textAbstract:
The rising of terrorism activities has promoted fast development of new construction materials to enhance the resistance and resilience of buildings and infrastructure against blast loads. As a notable representative, ultra-high performance concrete (UHPC) has now been widely investigated by government agencies and universities. UHPC inherits positive aspects of ultra-high strength concrete (UHSC) and it is equipped with improved ductility as a result of fibre addition. These features make it an ideal construction material for bridge decks, storage halls, thin-wall shell structures, and other infrastructure against seismic, impact and blast loads. In the thesis, development of novel UHPC material is presented. The new concrete material is distinguished from previous development by the inclusion of the nanoparticles. It was noticed that addition of nanoscale size particles results in significantly improved material properties without much change of the material composition. The present study focuses on influence of fibre material addition and nanomaterial addition on mechanical properties of UHPC material. In total, three kinds of steel fibre material with varying volume fraction are considered in the material design, in combination with four different nano materials at varying weight dosages. Discussion is carried out on fibre material geometry and fraction as well as nano particle effect. Static material tests are carried out to understand material strength and ductility. Uniaxial compressive tests and flexural tensile tests reveal the exceptional material strength, ductility as well as energy absorption capability. Since the material aims at improving the structural performance under extreme loading conditions, dynamic material properties are also of significant importance. Split Hopkinson Pressure Bar (SHPB) tests are conducted on UHPC samples, dynamic compression tests and split tensile tests are studied and compared with static material strength to obtain the dynamic increase factor which is critical in the design of material and structures against dynamic loads. All the above tests can be used to qualitatively and quantitatively examine the material performance with nano material and steel fibre material addition at macroscale. To further study the influence of these materials, microscopy analysis was conducted to provide explanation of macroscopic failure phenomenon at micro-scale. Morphology of the samples was observed by Scanning Electron Microscopy (SEM). X-Ray Diffraction (XRD) instrument was used for phase analysis and semi-quantitative analysis. Elemental analysis was conducted by X-Ray Fluorescence (XRF). In SEM tests on post-damage UHPC samples, different damage modes at ITZ are identified, XRD and XRF analysis confirmed the filling and pozzolanic effect of nano particles addition. In most cases, UHPC material can be treated as homogeneous at macroscopic scale, when observed at a smaller length scale, UHPC is heterogeneous and consists of constituents including aggregate, CH crystals, C-S-H gel, water and fibre material. It is impractical to consider all the phases in the microstructure of SFRC. In general, to investigate the interfacial transition zone (ITZ) effect on the fibre bonding properties, UHPC is described as multiphase material consisting of the cement paste, aggregates, fibres and ITZs among them. The existence of ITZs weakens the bonding between the fibres and concrete matrix. The bonding performance of UHPC is influenced by the fibre geometry, fibre orientation, and also the strength of the matrix, it is therefore critical to consider the ITZ effect in the performance of UHPC. In the current study, the bonding effect between the fibre material and matrix is investigated firstly by single fibre pull-out tests in which different fibre embedding depths are considered. The experimental results are then used to establish the bond-slip relationship in the numerical model. Three dimensional mesoscale model with consideration of both the concrete matrix and fibre phase is established. Model calibration is conducted with comparison to static material tests, further validation is obtained through SHPB split tensile test simulation. The proposed 3D mesoscale model can effectively model the material behaviour especially the post yielding ductility. With the understanding of the new material, field blast tests are carried out on concrete components constructed with this UHPC. Comparison is made against conventional concrete component and high strength concrete components, and the exceptional performance reveals its potentiality in the protective structural design.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2017.
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Wu, Jhih-wei, and 吳志偉. "The Study on the Effect of Micro-Nano Siliceous material on the Performance of Concrete." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/00435886512428604640.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
96
The study is mainly to observe the effect of adding fine fly ash and silica fume on the performance of concrete. The fly ash grain is fined by employing hydrocyclone classification technology to approach micro-nano sized particle. The parameters for hydrocyclone classification are the concentration of fly ash pulp and the jet pressure, and the final process chosen is based on particle size distribution, mean diameter (D50), and the production rate. It indicates the one with 10% fly ash concentration and 20 psi jet pressure has the optimum performance of hydrocyclone classification. The D50 of fined fly ash reduced 61% as compared to that of raw fly ash. Overflow fly ash, fine fly ash, and siliceous micro-nano material (raw fly ash and silica fume) are used to design high performance concrete by Hwang-Fuller’s Densified mixture design algorithm and evaluated their effects on the performance of concrete. The results show that through the fresh, hardened and durability properties of concrete, the one with fine fly ash are superior to that with the raw fly ash. Besides compressive strength, the engineering properties of concrete with the addition of fine fly ash is superior to those with silica fume. The SEM micrograph indicates the addition of siliceous micro-nano size material does improve the interface transition zone through dense filled effect and the Pozzolanic reaction.
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Yu-Jie, Ciou, and 邱裕傑. "Effect of Engineering Properties on High Performance Concrete with Nano-precipitated Calcium Carbonate and Slag." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/40125950967471391718.
Full textAbstract:
碩士國立雲林科技大學
營建工程系碩士班
100
The objective of this research is to investigate the workability, strength, durability, and using Nano-precipitated calcium carbonate and slag to replace cement in high performance concrete. Because the cement of concrete required, manufacturing process to produce CO2, negative impact on the environment. In this research, Nano-precipitated calcium carbonates are selected to replace cement, which can’t pollute the environment by carbonization method. Slag has pozzolanic reaction, can upgrade late strength, used to replace the cement to achieve the goal of reuse resources. The result of this research shows that the Nano-precipitated calcium carbonate can consume the workability of the high performance concrete.but replace the amount of 20% the late strength have upgraded.Slag have pozzolanic reaction, can upgrade late strength better than control group 2%~6%.Chloride penetration test can Pozzolanic reaction slag in the specimens, so that the penetration of the amount of replacement of cement significantly lower than the Nano-precipitated calcium.
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林威任. "Piezoelectric Properties of Nano-Quartz Powder Cement Piezoelectric Composites and Using to Monitor Concrete Strength." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/t8xk92.
Full textAbstract:
碩士國立高雄應用科技大學
土木工程與防災科技研究所
106
In order to improve the piezoelectric properties of cement piezoelectric composite materials (piezoelectric cement), nano-quartz powders with high dielectric constant are added as the admixture. And made into a piezoelectric cement sensor into a concrete cylindrical test specimen age measurement of impedance changes to monitor concrete strength. In order to find the best content of adding nano-quartz powders, nano-quartz powders to replace the cement volume content of 1% to 6%. In this study, the piezoelectric cement is composed of 50 vol.% of the PZT ceramic inclusion and cement substrates. Two grades of PZTs, a single-grading (PQ0) and medium-grading (MGQ0), were chosen to manufacture piezoelectric cement. Cement piezoelectric composites subjected to 1.5kV/mm electric field at 150°C to evoke their piezoelectric properties. Experimental results show that the PZT gradation affects the piezoelectric properties of piezoelectric cement without nano-quartz powders, but the effect of PZT grade paired piezoelectricity reduced when the nano-quartz powders adding to the piezoelectric cement. Materials with single-grading PQ0 and 4% nano-quartz powders have the best piezoelectric strain factor d33=103.3 pC/N, relative dielectric constant ɛr=544.6, with 30% increasing than piezoelectric cement without nano-quartz powders. The medium-grading piezoelectric cement has the best piezoelectric properties by adding 2% nano-quartz powder, with d33=103.8 pC/N and the relative permittivity ɛr=439.8. The electromechanical coupling coefficient κt of single-grading PQ0 has a best value of 17.07% at 4% nano-quartz powders. When the nano-quartz powders are up to 6%, the κt value has a 12.11% decrease. The medium-grading PZT and at 2% nano-quartz powders own the best κt value of 16.58%, but the optimum content of nano-quartz powders is 5% and the value of κt is 16.38% if temperature treatment is aPQ0lied. The concrete strength monitoring results showed that the conductance curves of PZT sensors in the frequency range of 400~440 kHz and 910~950 kHz decreased with the increase of the concrete age (1-28 days). The conductance curve of the piezoelectric cement (PQ0) sensor in the frequency range of 200~1000kHz decreases with the increase of the age. The nano-quartz piezoelectric cement (PQ4) has the same tendency as PZT and PQ0 sensors in the real part of impedance of frequency range 450 ~ 540kHz. Based on the results of RMSD and compressive strength regression analysis, PQ0 sensor is more suitable for monitoring or predicting the strength of concrete.
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Jeng, Yi-Fan, and 鄭逸凡. "Properties of High Performance Concrete Containing Nano-silica Powder under the corrosion of Strong Acid and Alkali." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/01921129095595495565.
Full textAbstract:
碩士國立高雄應用科技大學
土木工程與防災科技研究所
94
The concrete structures in chemical factories are often attacked by acid and alkali. This may cause the deterioration of concrete, decrease of the survival of structures and increase of the cost of maintenance. The purpose of this research is to investigate the properties of High Performance Concrete Containing Nano-silica Powder (NSHPC) under the corrosion of acid and alkali. In the first part of this disertation, we regulate the paste amount of concrete (n=1.3); the parameters are Water-binder ratio (W/B=0.24, 0.31 and 0.38) and varying content of Nano-silica powder (0% and 2%). Secondly, we regulate the Water-binder ratio (W/B=0.38); the parameters are paste amount (n=1.1, 1.3 and 1.5) and varying content of Nano-silica powder (0% and 2%). We also compare with Ordinary Portland Concrete (OPC, the design strength is 350 Kg/cm2). The test included Rapid resistance of acid and alkali, compressive strength, ultrasonic wave propagation velocity measurement, electrical resistivity, rapid chloride ion penetration test and Field emission scanning electron microscope (FE-SEM). The results show that the less of the Water-binder ratio and paste amount of High Performance Concrete (HPC) will make the better mechanical properties, low permeability, higher electrical resistivity and better anti-corrosion ability; while the anti-corrosion ability of OPC is bad. The adding of Nano-silica powder in HPC will raise the workability and anti-corrosion ability of HPC more effectively. After the hydration of Nano-silica powder, it will form Calcium Silicate Hydrate (C-S-H) gel and fill concrete pore making concrete densified. Namely, NSHPC owns fine anti-corrosion ability under acid and alkali attack.