To see the other types of publications on this topic, follow the link: Mechanical properties of concrete.
Dissertations / Theses on the topic 'Mechanical properties of concrete'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Mechanical properties of concrete.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Zhao, Jianwei. "Mechanical properties of concrete at early ages." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/6049.
Full textAbstract:
Modern construction techniques enable reinforced concrete structures to be constructed in a very short time. The loads occurring due to the construction process on the partially completed structure can be larger than the design service load. The available strength of the immature partially completed structure is dependent upon the available concrete strength which may be less than the specified strength. Failure would occur if the available strength is less than that required to support the construction loads. The construction loads can also cause significant immediate deflection due to concrete cracking and its low early age modulus of elasticity. Because of the high applied stress/developed strength ratio and shrinkage, the time dependent deflection may be unacceptably large. This thesis examines the early age behaviors of concrete tensile strength, modulus of elasticity, concrete shrinkage and creep, and develops prediction equations which are demonstrated to be more appropriate than the current code equations.
2
Downie, Brian. "Effect of moisture and temperature on the mechanical properties of concrete." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4240.
Full textAbstract:
Thesis (Ph. D.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains viii, 112 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 93-95).
3
Yurtseven, Alp Eren. "Determination Of Mechanical Properties Of Hybrid Fiber Reinforced Concrete." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605268/index.pdf.
Full textAbstract:
ABSTRACT
DETERMINATION OF MECHANICAL PROPERTIES OF
HYBRID FIBER REINFORCED CONCRETE
Yurtseven, Alp Eren
M.Sc. Department of Civil Engineering
Supervisor: Prof. Dr. Mustafa Tokyay
Co-Supervisor: Asst. Prof. Dr. . Özgü
r Yaman August 2004, 82 pages Fiber reinforcement is commonly used to provide toughness and ductility to brittle cementitious matrices. Reinforcement of concrete with a single type of fiber may improve the desired properties to a limited level. A composite is termed as hybrid, if two or more types of fibers are rationally combined to produce a composite that derives benefits from each of the individual fibers and exhibits a synergetic response. This study aims to characterize and quantify the mechanical properties of hybrid fiber reinforced concrete. For this purpose nine mixes, one plain control mix and eight fiber reinforced mixes were prepared. Six of the mixes were reinforced in a hybrid form. Four different types of fibers were used in combination, two of which were macro steel fibers, and the other two were micro fibers. Volume percentage of fiber inclusion was kept constant at 1.5%. In hybrid reinforced mixes volume percentage of macro fibers was 1.0% whereas the remaining fiber inclusion was v composed of micro fibers. Slump test was carried out for each mix in the fresh state. 28-day compressive strength, flexural tensile strength, flexural toughness, and impact resistance tests were performed in the hardened state. Various numerical analyses were carried out to quantify the determined mechanical properties and to describe the effects of fiber inclusion on these mechanical properties. Keywords: Fiber Reinforcement, Hybrid Composite, Toughness, Impact Resistance
4
Hartell, Julie Ann. "Sodium sulphate attack on concrete: effect on mechanical properties." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19233.
Full textAbstract:
Traditionally, the extent of sulphate attack is qualified through visual rating as suggested by the Portland Cement Association, or quantified by the percent expansion of slender bars submerged in sulphate solution, the ASTM C 1012 standard. There are no standard methods that take into account the change in engineering properties due to sulphate attack's deleterious mechanisms. Moreover, the exposure regime used to evaluate sulphate attack, complete immersion, is not necessarily representative of that encountered in the field. For these reasons, the objective of this thesis is to quantify the degree of sodium sulphate attack through the degradation of mechanical properties, specifically the compressive and splitting tensile load capacities of standard cylindrical specimens. The research work presented herein also utilizes a novel exposure regime wherein the specimens are only partially submerged in 5% sodium sulphate solution, creating an evaporation front similar to that of field exposure.Traditionnellement, la méthode par inspection visuelle est suggérée pour qualifier le degré d'une attaque sulfatique du béton. Pour sa part, la norme ASTM C 1012 est régulièrement utilisée dans le cas où le pourcentage d'allongement d'un prisme en mortier submergé dans une solution de sulfate de sodium quantifie la résistance du ciment composant le mortier par rapport aux mécanismes d'expansion. Toutefois, le changement des propriétés d'ingénierie du béton, causé par les effets néfastes de l'attaque sulfatique, n'est pas pris en considération dans les normes existantes. Ainsi, le régime d'exposition aux sulfates de la norme ASTM C 1012, soit l'immersion complète, ne représente pas nécessairement ceux des ouvrages en béton. Pour ces raisons, l'objectif de cette thèse est de quantifier le niveau d'une attaque sulfatique à travers la dégradation des propriétés mécaniques du béton, soient les capacités en compression et tension d'un cylindre standard en béton. De plus, les travaux de recherche incluent un nouveau régime d'exposition afin de recréer un front d'évaporation similaire à celui d'un ouvrage en béton semi-saturé. Comparativement, les spécimens en béton sont submergés jusqu'à leur mi-hauteur dans une solution de sulfate de sodium.
5
Zanganeh, Mehdi. "Mechanical properties of fiber reinforced concrete with ACM applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0013/MQ52021.pdf.
Full text
6
Mohammed, Hafeez. "Mechanical Properties Of Ultra High Strength Fiber Reinforced Concrete." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1431021338.
Full text
7
Chapagain, Indra Prasad. "Mechanical properties of self-consolidating concrete with pozzolanic materials." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/2111.
Full textAbstract:
Self-consolidating concrete has been described as the most revolutionary development in concrete technology in several decades with the ability to flow freely through closely spaced reinforcements, expel entrapped air and self compact without vibration. Since it was first developed in Japan in the early 1980's, major development in the chemical admixture technology has made SCC more viable.
An experimental study was conducted to identify the mechanical properties of SCC by optimizing the use of pozzolanic materials and local aggregates with some proposed statistical models. The research was focused to investigate compressive strength, splitting tensile strength, modulus of elasticity and drying shrinkage behavior of concrete. The results were established experimentally and compared with the available SCC research data based on extensive literature study.
Besides the improved mechanical performance, results indicate that the use of pozzolanic materials and local aggregate in SCC is recommended in terms of its cost benefit value.
8
Brockmann, Tanja. "Mechanical and fracture mechanical properties of fine grained concrete for textile reinforced composites." Aachen : Mainz, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=97972127X.
Full text
9
Eskander, Ashraf. "EFFECTS OF FIBER AND LITHIUM ON MECHANICAL PROPERTIES OF CONCRETE MADE FROMRECYCLED CONCRETE AGGREGATE." Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2954.
Full textAbstract:
The growing demand of construction aggregates has raised concern about the availability of natural aggregates. Over two billion tons of natural aggregate are produced each year in the United States and that number is expected to increase to 2.5 billion tons by 2020. This has raised concern about the availability of natural aggregate. Discarding demolished concrete into landfills is a costly solution from an economical and environmental point of view. Many U.S. highway agencies are re-using Recycled Concrete Aggregates (RCA) as construction material. The use of fiber reinforcement in Portland Cement Concrete (PCC) has recently become a popular option in concrete construction because of its influence on preventing segregation, reducing early shrinkage cracks and increasing residual load capacity. Alkali-Silica Reaction (ASR) is a major problem in concrete, especially when using RCA, causing concrete expansion and cracks. Recently lithium has been found to reduce expansion due to ASR. This thesis will investigate the effect, of fibers soaked in lithium nitrate on the mechanical properties of RCA.M.S.C.E.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering
10
Boukendakdji, Mustapha. "Mechanical properties and long-term deformation of slag cement concrete." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236998.
Full text
11
Li, Xincheng. "Mechanical properties and durability performance of reactive magnesia cement concrete." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607703.
Full text
12
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.
Full textAbstract:
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
13
Hakimelahi, Hamed. "Investigation of fracture properties of California asphalt concrete mixtures." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527553.
Full textAbstract:
Fatigue cracking is a primary distress in asphalt due to repetitive stresses and strains caused by traffic. The main objective of this study is to investigate the use of the semi-circular bend (SCB) test as a quality assurance/quality control (QA/QC) measure for field construction.
The SCB test parameters were determined using two methods, the first of which was cross-head movement (CHM), and the second was non-contact camera. In SCB CHM method the specimens were loaded monotonically until fracture under a constant cross-head deformation, while in none-contact camera method a camera was fixed in front of the SCB specimen to measure the crack length. In addition beam-fatigue test (BFT) was conducted according to AASHTO T-321 on the same mixtures.
A comprehensive comparison between the test results is performed. The results of this study indicate that the SCB test has a great potential as a QA/QC test of fracture properties of asphalt mixtures.
14
Ryno, Barnard. "Mechanical properties of fly ash/slag based geopolymer concrete with the addition of macro fibres." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95866.
Full textAbstract:
Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: Geopolymer concrete is an alternative construction material that has comparable mechanical properties to that of ordinary Portland cement concrete, consisting of an aluminosilicate and an alkali solution. Fly ash based geopolymer concrete hardens through a process called geopolymerisation. This hardening process requires heat activation of temperatures above ambient. Thus, fly ash based geopolymer concrete will be an inadequate construction material for in-situ casting, as heat curing will be uneconomical. The study investigated fly ash/slag based geopolymer concrete. When slag is added to the matrix, curing at ambient temperatures is possible due to calcium silicate hydrates that form in conjunction with the geopolymeric gel. The main goal of the study is to obtain a better understanding of the mechanical properties of geopolymer concrete, cured at ambient temperatures. A significant number of mix variations were carried out to investigate the influence that the various parameters, present in the matrix, have on the compressive strength of fly ash/slag based geopolymer concrete. Promising results were found, as strengths as high as 72 MPa were obtained. The sodium hydroxide solution, the slag content and the amount of additional water in the matrix had the biggest influence on the compressive strength of the fly ash/slag based geopolymer concrete. The modulus of the elasticity of fly ash/slag based geopolymer concrete did not yield promising results as the majority of the specimens, regardless of the compressive strength, yielded a stiffness of less than 20 GPa. This is problematic from a structural point of view as this will result in large deflections of elements. The sodium hydroxide solution had the most significant influence on the elastic modulus of the geopolymer concrete. Steel and polypropylene fibres were added to a high- and low strength geopolymer concrete matrix to investigate the ductility improvement. The limit of proportionality mainly depended on the compressive strength of the geopolymer concrete, while the amount of fibres increased the energy absorption of the concrete. A similar strength OPC concrete mix was compared to the low strength geopolymer concrete and it was found that the OPC concrete specimen yielded slightly better flexural behaviour. Fibre pull-out tests were also conducted to investigate the fibre-matrix interface. From the knowledge gained during this study, it can be concluded that the use of fly ash/slag based geopolymer concrete, as an alternative binder material, is still some time away as there are many complications that need to be dealt with, especially the low modulus of elasticity. However, fly ash/slag based geopolymer concrete does have potential if these complications can be addressed.
AFRIKAANSE OPSOMMING: Geopolimeerbeton is ‘n alternatiewe konstruksiemateriaal wat vergelykbare meganiese eienskappe met beton waar OPC die binder is, en wat bestaan uit ‘n aluminosilikaat en ‘n alkaliese oplossing. Vliegas-gebaseerde geopolimeerbeton verhard tydens ‘n proses wat geopolimerisasie genoem word. Hierdie verhardingsproses benodig hitte-aktivering van temperature hoër as dié van die onmiddellike omgewing. Gevolglik sal vliegas-gebaseerde geopolimeerbeton ‘n ontoereikende konstruksiemateriaal vir in situ gietvorming wees, aangesien hitte-nabehandeling onekonomies sal wees. Die studie het vliegas/slagmentgebaseerde geopolimeerbeton ondersoek. Wanneer slagment by die bindmiddel gevoeg word, is nabehandeling by omliggende temperature moontlik as gevolg van kalsiumsilikaathidroksiede wat in verbinding met die geopolimeriese jel vorm. Die hoofdoel van die studie was om ‘n beter begrip te kry van die meganiese eienskappe van geopolimeerbeton, wat nabehandeling by omliggende temperature ontvang het. ‘n Aansienlike aantal meng variasies is uitgevoer om die invloed te ondersoek wat die verskeie parameters, aanwesig in die bindmiddel, op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton het. Belowende resultate is verkry en sterktes van tot so hoog as 72 MPa is opgelewer. Daar is gevind dat die sodiumhidroksiedoplossing, die slagmentinhoud en die hoeveelheid water in die bindmiddel die grootste invloed op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton gehad het. Die styfheid van die vliegas/slagmentgebaseerde geopolimeerbeton het nie belowende resultate opgelewer nie. Die meeste van die monsters, ongeag die druksterkte, het ‘n styfheid van minder as 20 GPa opgelewer. Vanuit ‘n strukturele oogpunt is dit problematies, omdat groot defleksies in elemente sal voorkom. Die sodiumhidroksiedoplossing het die grootste invloed op die styfheid van die vliegas/slagmentgebaseerde geopolimeerbeton gehad. Staal en polipropileenvesels is by ‘n hoë en lae sterke geopolimeer beton gevoeg om die buigbaarheid te ondersoek. Die die maksimum buigbaarheid het hoofsaaklik afgehang van die beton se druksterkte terwyl die hoeveelheid vesels die beton se energie-opname verhoog het. ‘n OPC beton mengsel van soortgelyke sterkte is vergelyk met die lae sterkte geopolimeerbeton en daar is gevind dat die OPC beton ietwat beter buigbaarheid opgelewer het. Veseluittrektoetse is uitgevoer om die veselbindmiddel se skeidingsvlak te ondersoek. Daar kan tot die gevolgtrekking gekom word dat, alhoewel belowende resultate verkry is, daar steeds sommige aspekte is wat ondersoek en verbeter moet word, in besonder die styfheid, voordat geopolimeerbeton as ‘n alternatiewe bindmiddel kan optree. Volgens die kennis opgedoen tydens hierdie studie, kan dit afgelei word dat die gebruik van vliegas/slagmentgebaseerde geopolimeerbeton, as 'n alternatiewe bindmiddel, nog 'n geruime tyd weg is, as gevolg van baie komplikasies wat gehandel moet word, veral die lae elastisiteitsmodulus. Tog het vliegas/slagmentgebaseerde geopolimeerbeton potensiaal as hierdie komplikasies verbeter kan word.
15
Wong, Kong-yeung. "Development of high strength concrete for Hong Kong and investigation of their mechanical properties /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19667711.
Full text
16
Kammouna, Zainab. "Effect of creep strains on the residual mechanical properties of concrete." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI038/document.
Full textAbstract:
L'objectif de cette thèse est d’étudier l'influence du fluage sur les propriétés mécaniques résiduelle du béton. En effet, les sections des éléments d’une structure précontrainte sont majoritairement soumise à une contrainte de compression. En raison de la relaxation des contraintes (due au fluage du béton notamment) et de la charge appliquée, des contraintes de traction peuvent apparaitre au cours de la vie de l’ouvrage. Ainsi, il est nécessaire de connaître la valeur des propriétés mécaniques résiduelles après l'effet de fluage.Le travail se concentre sur le fluage propre (sans échange hydrique avec le milieu environnant) et il comprend une partie expérimentale et une partie numérique. Dans la partie expérimentale, des essais de fluage en compression et en traction indirect (essai Brésilien) ont été effectués sur le béton en utilisant différents niveaux de chargement appliqué à différents âges du béton. A la fin de chaque essai de fluage, un essai quasi statique a été réalisé sur le même béton pour déterminer l'effet du fluage sur les propriétés mécaniques résiduelles. Afin de vérifier l'effet d’une précharge en compression sur la résistance en traction, comme dans le cas d’une structure précontrainte vieillissante ou soumise à un chargement accidentelle, une campagne d’essai Bresilien avec un préchargement quasi statique en compression a également été réalisée. Les résultats montrent que le comportement après fluage dépend fortement de l’âge de chargement et du sens de sollicitation. Numériquement, un modèle mésoscopiques a été utilisé pour simuler le fluage et les propriétés mécaniques après fluage. En effet, sous un chargement constant seule la pâte de ciment flue tandis que les agrégats agissent comme un obstacle à ce fluage. Par conséquent, les contraintes de traction se produisent à l'interface pâte de ciment/agrégats conduisant à microfissures dans cette zone Les déformations viscoélastique sont correctement reproduite à différents niveaux de chargement mais la modification du comportement résiduel du béton ne peut pas être uniquement expliqué par la micro-fissurationThe aim of this study is to evaluate the effect of creep on the concrete mechanical properties evolution. In prestress structures, in the first concrete is completely subjected to compressive stresses. With time, due to relaxation of the prestressed cables and applied load, some tensile stresses may take place in the concrete. So, it is necessary to know the value of the residual mechanical properties after creep effect.The work which concerns only with basic creep (where there is no drying), includes an experimental part and a numerical part. In the experimental part, compressive and tensile (Brazilian) creep tests were carried out on the concrete using different loading levels that applied at different ages of concrete.At the end of each creep test a strength test was carried out on the same concrete for determining the creep effect on the residual mechanical properties. To evaluate the effect of quasi-instantaneous loading in compression and then in tension, some preloading compressive tests were carried out. These tests were accomplished especially to distinguish the effect of quasi-instantaneous effect from that of creep. A quasi-instantaneous compressive test was achieved until a given level and then a Brazilian strength test was carried out to evaluate the effect of compressive preloading on the tensile strength.Numerically, a mesoscopic model was developed for simulating creep and mechanical properties after creep had taken place. The reason for which this mesoscopic technique was used is related to the fact that under the considered loading level of concrete, only the cement paste creeps while the aggregate act as an obstacle to this creep. As a result, tensile stresses arise at cement past-aggregate interface leading to micro cracks at this zone. With this technique, creep strain can generate some damage at mesoscale without any coupling between creep and damage as in sence phenomenological models
17
Bajaj, Srikanth. "Effect of Corrosion on Physical and Mechanical Properties of Reinforced Concrete." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353961865.
Full text
18
Mumenya, Siphila Wanjika. "Evaluation of mechanical properties of textile concrete subjected to different environmental exposures." Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5499.
Full textAbstract:
Includes bibliographical references (leaves 310-327).Within the last decade, a new class of civil engineering materials referred to as High Performance Fibre Reinforced Cementitious Composites (HPFRCC) has been developed. As a subset in this new field, additions of polypropylene (PP) fibres, in the form of woven textile fabrics, have proved most successful as reinforcement to cementitious matrices, leading to the development of a novel composite material: so called "Textile Concrete" (TC). Although the strength and modulus of PP are not very high, careful design through the appropriate placement and high fibre volume fraction of a textile format, has led to sufficient strength and stiffness, while at the same time high toughness has been achieved. In particular the development of a fibrillated core fibre to which is attached an outer layer of ultrasonically welded, or bonded "fluffy" PP fibres, has been most successful, and is a unique feature. These outer fluffy layers provide excellent physical bonding characteristics to the cement matrix, thus overcoming the intrinsic hydrophobic nature and otherwise weak matrix bonding of PP fibres. In South Africa where TC has found ready application, the composite is produced from a fine grained cementitious matrix and a PP textile commercially known as CemForce.
19
Hayles, Meika. "Investigation Into the Mechanical Properties and Structural Behaviour of Recycled Concrete Members." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37801.
Full textAbstract:
Recycled concrete aggregates (RCA) are an eco-sustainable alternative to traditional aggregates. The equivalent mortar volume method has been developed to design RCA concrete with comparable mechanical and strength properties to natural aggregate concrete by accounting for the adhered mortar that distinguishes RCA from natural aggregates. This method also presents an opportunity to reduce the cement content of RCA concrete, increasing its cement efficiency. Modifications to mix design procedures were introduced to improve the fresh state properties of RCA concrete with a 19% cement reduction compared to the control mix. Beams cast with the RCA concrete had similar flexural capacity to corresponding control beams, however the shear strength varied as a function of RCA content in the concrete. Polished core samples taken from RCA members showed that crack development and aggregate interlock in RCA members is influenced by the aggregate properties and the spacing of coarse aggregates, indicating that knowing the compressive strength of RCA concrete is not the only parameter required for member design.
20
Langdon, Sheldon. "The effects of alkali-aggregate reactivity on the mechanical properties of concrete." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0002/MQ36145.pdf.
Full text
21
Nehdi, Moncef. "Microfiller effect on rheology, microstructure, and mechanical properties of high-performance concrete." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0002/NQ27211.pdf.
Full text
22
Huda, Sumaiya Binte. "Mechanical and durability properties of recycled and repeated recycled coarse aggregate concrete." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46068.
Full textAbstract:
Disposal and treatment of construction and demolition (C&D) wastes are often costly and
hazardous to the environment. Their recycling could lead to a greener solution to the
environmental conservation and pave the way towards sustainability. This study utilizes
demolished concrete as coarse aggregate often termed as recycled coarse aggregate (RCA) for
producing industry quality concrete. Large scale recycling can substantially reduce the
consumption of natural aggregate and help preserve the environment. However, in near future, it
can raise new challenges. The use of “repeated recycled coarse aggregate” in concrete production
can be a viable solution to the growing problem regarding the C&D waste disposal. During the
development of new generation product like recycled and repeated recycled coarse aggregate
concrete, it is essential to investigate the fresh, hardened, and durability properties of concrete to
promote and escalate its application in the construction industry. This research investigates the
fresh, mechanical, and durability properties of 25 MPa recycled aggregate concrete (RAC) made
with different RCA replacement levels. Durability performance of 25 MPa RAC was evaluated
in terms of sulphate attack and cyclic wetting and drying along with chloride exposure. Chloride
propagation was evaluated after 1, 4, 9, 16, 28, 90, and 120 cycles. This study reveals that the
performance of RAC is decreasing with increasing RCA replacement levels but their overall
performance is comparable to natural aggregate concrete (NAC).
Three different generations of repeated recycled coarse aggregate concrete were produced
using 100% RCA as a replacement of natural coarse aggregate. Similar mix design was used for
producing 32 MPa concrete. Along with this, their durability performance was examined under
three different exposure conditions namely, freeze-thaw, sulphate, and chloride exposure. It was
found that the compressive strength of different generations of repeated recycled concrete was lower than the control concrete. However, all of the mixes exceeded the target strength at 120
days. The durability performance of the different generations of repeated recycled coarse
aggregate concrete was negatively affected by using different generations of such aggregates but
still these findings will add a new achievement towards sustainable world.
23
Othuman, Mydin Md Azree. "Lightweight foamed concrete (LFC) thermal and mechanical properties at elevated temperatures and its application to composite walling system." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/lightweight-foamed-concrete-lfc-thermal-and-mechanical-properties-at-elevated-temperatures-and-its-application-to-composite-walling-system(5a13ec7f-d460-4354-a296-6d1ffecff971).html.
Full textAbstract:
LFC is cementatious material integrated with mechanically entrained foam in the mortar slurry which can produce a variety of densities ranging from 400 to 1600 kg/m3. The application of LFC has been primarily as a filler material in civil engineering works. This research explores the potential of using LFC in building construction, as non-load-bearing partitions of lightweight load-bearing structural members. Experimental and analytical studies will be undertaken to develop quantification models to obtain thermal and mechanical properties of LFC at ambient and elevated temperatures. In order to develop thermal property model, LFC is treated as a porous material and the effects of radiant heat transfer within the pores are included. The thermal conductivity model results are in very good agreement with the experimental results obtained from the guarded hot plate tests and with inverse analysis of LFC slabs heated from one side. Extensive compression and bending tests at elevated temperatures were performed for LFC densities of 650 and 1000 kg/m3 to obtain the mechanical properties of unstressed LFC. The test results indicate that the porosity of LFC is mainly a function of density and changes little at different temperatures. The reduction in strength and stiffness of LFC at high temperatures can be predicted using the mechanical property models for normal weight concrete provided that the LFC is based on ordinary Portland cement. Although LFC mechanical properties are low in comparison to normal weight concrete, LFC may be used as partition or light load-bearing walls in a low rise residential construction. To confirm this, structural tests were performed on a composite walling system consisting of two outer skins of profiled thin-walled steel sheeting with LFC core under axial compression, for steel sheeting thicknesses of 0.4mm and 0.8mm correspondingly. Using these test results, analytical models are developed to calculate the maximum load-bearing capacity of the composite walling, taking into consideration the local buckling effect of the steel sheeting and profiled shape of the LFC core. The results of a preliminary feasibility study indicate that LFC can achieve very good thermal insulation performance for fire resistance. A single layer of 650 kg/m3 density LFC panel of about 21 mm would be able to attain 30 minutes of standard fire resistance rating, which is comparable to gypsum plasterboard. The results of a feasibility study on structural performance of a composite walling system indicates that the proposed panel system, using 100mm LFC core and 0.4mm steel sheeting, has sufficient load carrying capacity to be used in low-rise residential construction up to four-storeys.
24
Brockmann, Tanja [Verfasser]. "Mechanical and fracture mechanical properties of fine grained concrete for textile reinforced composites / vorgelegt von Tanja Brockmann." Aachen : Mainz, 2006. http://d-nb.info/97972127X/34.
Full text
25
Espinoza, A., A. Espinoza, B. Jiménez, J. Rodríguez, and C. Eyzaguirre. "Mechanical Properties of an Eco-friendly Concrete with partial replacement of POC and Rubber." Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/651793.
Full textAbstract:
Concrete plants consume 10 billion tons of natural aggregates annually from quarries and gravel plants for produce concrete, this demand requires exploiting natural resources from mountains and rivers producing an ecological imbalance. One solution is to use Palm Oil Clinker (POC), which is eliminated in large quantities in the dumps and rivers without taking advantage of its puzolanic, binding and resistance properties as an aggregate in the concrete; another alternative is to apply rubber from abandoned and discarded tires as waste in landfills or burned, without taking advantage of its performance of improvement in concrete, increasing its resistance to impact and fatigue. Unable to find joint POC and rubber information, this research studies its influence replacing 2.5% rubber (grained and crushed) with 10%, 12.5% and 15% POC in the fine aggregate on traditional concrete; results indicate that with 12.5% of POC as the ideal percentage, the compressive strength, tensile strength and flexural strength rise between 2.16 - 9.54%, so the concrete obtained has a cost of less than 4.09% and has 3.65% less CO2 emission.
26
Annam, Ramyasree. "Study of Mechanical Properties of PVA Fiber-Reinforced Concrete With Raman Spectroscopic Analysis." TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1460.
Full textAbstract:
The brittleness of concrete has always been a safety and economic issue of great concern. The low tensile strength of concrete is the cause of its intrinsic brittle nature. This is critical considering the amount of concrete used for the construction of highways, buildings, and other facilities. The mechanical properties of concrete must be improved to provide upgraded construction. Crack resistant and durable concrete has always been a major goal for engineers. Many approaches have been tried to make concrete a better construction material. Fiber reinforcement is an approach which has been shown to improve the quality and durability of concrete. The focus of this research is to develop a mix design of fiber reinforced concrete and then test these materials for both compressive and tensile strength after casting into cubes. The effect of polyvinyl alcohol fibers on the mechanical properties of concrete was also studied. The impacts of moisture and the stress applied on the fibers were determined using Raman spectroscopy.
27
Fagotti, Francesco. "Mechanical properties of circular concrete made with 100% recycled aggregates from construction and demolition waste." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Find full textAbstract:
Nowadays, one of the main focuses of the concrete industry is to have environmental friendly buildings to reduce the relentless rise of GHG emissions. The majority of energy and GHG emissions embodied in concrete are due to use of cement and it is responsible for more than 50% of the CO2-emission. This research has been held in the Faculty of Civil Engineering and Geosciences of the of Delft and it concerns the mechanical properties of circular concrete, which is made of 100% recycled aggregates from construction and demolition waste. This investigation is placed within a project about particle packing technologies and the objective of the latter is to optimize the particle size distribution of aggregates and understand the compaction of concrete made of recycled aggregates. Particle size optimization is aimed to improve the density of concrete made of regularly packed aggregates and the distribution of voids thereby improving its sustainability and strength, leading to considerable CO2 reduction. Three recipes have been designed to employ different types of aggregates. The water to cement ratio of recipes was adjusted based on the magnitude of the slump. In particular, recycled aggregates (<12mm) and natural aggregates of different sizes (<12mm and <16 mm) are used. The role of maximum aggregates size and effect of complete substitution of natural aggregates with recycled aggregates has been studied. The recipes have been casted by varying the duration of vibration in order to understand the role of vibration on the compressive strength and the distribution of air bubbles inside the concrete. Results indicate that the duration of vibration was observed to be critical depending on the type and size of aggregate. Despite direct relation of vibration and internal pores, the impact seems to be negative beyond some time. Meanwhile, the compaction and mechanical property of concrete made of recycled aggregates need more vibration compared to natural aggregates.
28
Ay, Lutfi. "Steel fibrous cement based composites: material and mechanical properties : behavior in the anchorage zones of prestressed bridges." Doctoral thesis, KTH, Civil and Architectural Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3844.
Full textAbstract:
This PhD thesis is divided into two parts. Part one dealswith the development of the material and the mechanicalproperties of Steel Fibrous Cement Based Composites (SFCBC) forimproving bridge design and construction. It familiarizes thehydration mechanisms of the high performance concrete with thehelp of Powers´ and Jensen´s models. Concretes withdifferent water-cement ratio were compared with each other withrespect to degree of hydration and hydration products. Thisanalysis showed that high performance concrete has higherstrengths not because it has more gel solid, but due to ithaving less porosity and higher filler content compared toordinary concrete.
A number of experiments were performed to achieve a mixdesign method for a SFCBC, which has good workability, highearly and long-term strength and good durabilitycharacteristics. A Self-compacting and self-leveling fibrouscomposite, which has ultra high strengths (Compressive strengthfc= 180 ~ 220MPa and flexural tensile strengthfföi= 14 ~ 32MPa depending on the volumefraction of fibers) was produced. This composite was alsotested under different curing conditions in order toinvestigate the effect of curing on hydration andself-desiccation shrinkage. These tests showed that SFCBCshould not be water-cured under a long period andself-desiccation influences the compressive strengthnegatively. Test of scaling at freezing showed that SFCBC hasvery good durability characteristics.
Part two deals with the behavior of SFCBC in the anchoragezones of prestressed bridges. The prismatic composite specimenswere tested for different volume fractions of fibers underdifferent concentrations ratios of strip loading. The resultsof these tests showed that the ultimate strength of the SFCBCspecimens was approximately twice that of ordinary concretewith the same size (fc= 60MPa reinforced with stirrups). Therefore,SFCBC has good possibility to replace the traditional rebars inthe anchorage zones of prestressed bridges.
This composite has different behavior than the traditionalconcrete e.g. crack formation, failure criteria, effectivestrength and angle of friction. A vertical crack on thecenterline was occurred while wedge developed under the loadingplate. In contrast to ordinary concrete, the cracks could notreach to the bottom of the blocks.
The tests results gave the ideas of that this material actslike metals or plastics in the high fiber content. Thismaterial is neither very brittle as concrete nor very ductileas metals but it is somewhere between them.
Upper-bound plasticity solutions were utilized for modelingthe bearing capacity of SFCBC. Predictions of this method aregood enough to estimate the bearing capacity of SFCBC in theanchorage zones of prestressed bridges.
Keywords:Process improvement of bridges, Prestressedconcrete, High performance concrete, Ultra high performanceconcrete, Hydration, Cement based composites, Fibers,Self-compacting concrete, Bearing capacity, Anchorage zones,Tests
29
Kim, Byoungil. "Effect of fiber types on the mechanical properties and permeability of high strength concrete." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015827.
Full text
30
Wong, Kong-yeung, and 黃剛揚. "Development of high strength concrete for Hong Kong and investigation of their mechanical properties." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31213765.
Full text
31
Gea, dos Santos Fabio Luis 1989. "Estudo e automação da influência da taxa de carregamento na resposta em fratura quase-frágil." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258435.
Full textAbstract:
Orientador: José Luiz Antunes de Oliveira e SousaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-26T02:16:10Z (GMT). No. of bitstreams: 1 GeadosSantos_FabioLuis_M.pdf: 8564383 bytes, checksum: 72e9522142ccde293049d4563ab69368 (MD5) Previous issue date: 2014
Resumo: Nos últimos anos, o aumento no número de construções mais altas e complexas fez com que o estudo das propriedades mecânicas do concreto na ruptura em tração fosse foco de muitas pesquisas. O concreto desenvolve, durante o carregamento, diferentes processos de coalescência e crescimento de micro-fissuras e, devido a sua natureza heterogênea, um enorme esforço ainda é requerido para o desenvolvimento de um modelo constitutivo capaz de descrever aspectos relevantes do seu comportamento. A essa premissa soma-se a discussão da validade dos procedimentos de ensaio em descrever o comportamento real do material, devido à influência estrutural (forma da geometria, condições de contorno e tamanho) do espécime de teste. O comportamento quase-frágil do concreto, caracterizado pelo desenvolvimento de uma zona de processos inelásticos e/ou zona de processos de fratura (ZPF) ao redor do fronte da trinca, quando na ruptura em tração, requer uma lei constitutiva ¿ chamada lei coesiva, curva tensão-abertura de fissura (? ¿ w), curva de amolecimento ou função coesiva (?=f(w)) ¿ que relaciona a tensão desenvolvida no fronte da fratura, isto é na ZPF, e a sua abertura como ingrediente para modelagem da nucleação e da propagação da fratura, seja esta representada de maneira implícita e/ou explícita. Desenvolveu-se um software para a determinação automática da lei constitutiva utilizando-se curvas da relação carga versus abertura da boca fratura (load versus crack mouth opening displecement ¿ P-CMOD) ou da relação carga versus deslocamento no ponto de aplicação (P-?) obtidas em ensaios com vigas prismáticas ranhuradas em flexão em três pontos (Three-Point-Bend Test), com taxas de carregamento variada. O objetivo desse trabalho é avaliar a lei coesiva-viscosa proposta por Rosa et al. (2012) utilizando o software desenvolvido para o ajuste de curvas P-? numéricas com curvas de vigas ranhuradas de concreto de alta resistência, ensaiadas com taxas de carregamento variando da ordem de ? ?=?10?^(-5) mm/s a ? ?=?10?^(+1) mm/s
Abstract: In recent years, the increase of high and more complex constructions, many researches focus on the study of the mechanical properties of concrete at failure. The concrete under loading develops different processes of coalescence and growth of micro-cracks, and due to its heterogeneous nature, a great effort is still required to develop a constitutive model capable of describing the relevant aspects of its behavior. In addition to this premise is the discussion of validity of tests that describe the real behavior of the material, due to the structural influence (shape of the geometry, boundary conditions and size) of the test specimen. The quasi-brittle behavior of concrete, characterized by the development of a zone of inelastic processes and/or fracture processes (ZPF) around the crack front at failure, requires a constitutive law ¿ called cohesive law curve stress-crack opening (? ¿ w), softening or cohesive function (?=f(w)) ¿ curve that relates the stress developed across the front of the fracture, i. e., the ZPF, and its opening displacement as an ingredient for modeling fracture nucleation and propagation, represented implicitly and/or explicitly. A software developed for automatic determination of a constitutive law using curves of load versus relative fracture mouth opening (P-CMOD) or the load versus displacement relationship at the application line (P-?) obtained in tests with notched prismatic beams in Three-point Bend Test, with varying loading rates. This study aims at the evaluation of the viscous-cohesive model proposed by Rosa et al. (2012), using a software developed for the curve fitting P-? numerical curve with notch beams of high strength concrete, tested with loading rate numerical in the order between ? ?=?10?^(-5) mm/s and ? ?=?10?^(+1) mm/s
Mestrado
Estruturas e Geotécnica
Mestre em Engenharia Civil
32
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.
Full textAbstract:
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.
33
Hu, Hang. "Mechanical properties of blended steel fibre reinforced concrete using manufactured and recycled fibres from tyres." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/21168/.
Full text
34
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.
Full textAbstract:
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.
35
He, Qinyue. "The Study of Comprehensive Reinforcement Mechanism of Hexagonal Boron Nitride on Concrete." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804976/.
Full textAbstract:
The addition of hexagonal boron nitride (h-BN) has introduced a comprehensive reinforcing effect to the mechanical and electrochemical properties of commercial concrete, including fiber reinforced concrete (FRC) and steel fiber reinforced concrete (SFRC). Although this has been proven effective and applicable, further investigation and study is still required to optimize the strengthen result which will involve the exfoliation of h-BN into single-layered nano sheet, improving the degree of dispersion and dispersion uniformity of h-BN into concrete matrix. There is currently no direct method to test the degree of dispersion of non-conductive particles, including h-BN, in concrete matrix, therefore it is necessary to obtain an analogous quantification method like SEM, etc. The reinforcing mechanism on concrete, including FRC and SFRC is now attracting a great number of interest thanks to the huge potential of application and vast demand across the world. This study briefly describes the reinforcing mechanism brought by h-BN. In this study, different samples under varied conditions were prepared according to the addition of h-BN and dispersant to build a parallel comparison. Characterization is mainly focused on their mechanical properties, corrosive performance and SEM analysis of the cross-section of post-failure samples.
36
Chang, Lei. "Experimental Data on Fire-Resistance Behavior of Reinforced Concrete Structures with Example Calculations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3003/.
Full textAbstract:
This thesis selects concrete, steel and their relation as research subjects, mainly commentary and discusses the property changes of steel and concrete materials under and after high temperature.The differences and comparisons of reasearch methods and ways between different researchers and different papers,particularly for chinese researches and chinese papers,and partly for comparison between chinese papers methods and Euro-Amercian papers methods about Fire Resistance Behavior of Reinforced Concrete will be summarized and analyzed.The researches on fire-resistance behavior of reinforced concrete become more and more important all over the world. And I would find differences between Chinese researches results, between Chinese researches results and other countries researches results.
37
Babalola, O. E., P. O. Awoyera, M. T. Tran, D. H. Le, O. B. Olalusi, A. Viloria, and D. Ovallos-Gazabon. "Mechanical and durability properties of recycled aggregate concrete with ternary binder system and optimized mix proportion." Elsevier Editora Ltda, 2020. http://hdl.handle.net/10757/656774.
Full textAbstract:
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.This study aimed to investigate the mechanical and durability properties of recycled aggre-gate concrete with a ternary binder system and optimized mix proportion. Two concretebatches were developed using a densified mix design approach (DMDA) to evaluate therequired mix proportions. Batch I have GGBS content varied at 0%, 10%, 20%, 30%, 40% and50% at constant w/b ratio of 0.45, while batch II concrete mix have varied water/binder ratios:0.3, 0.35, 0.4, 0.45 and 0.5 at constant GGBS replacement level of 30%. The fine aggregate(river sand) of the two batches was blended with fly ash at optimum loose packing density(FA + Sand) and superplasticizer (SP) was incorporated in the mix at a constant level of 1.4%.A control mix comprising of natural aggregate was also developed. The results obtainedshowcased the feasibility of producing structural concrete with recycled aggregates usingGGBS and fly ash. The mechanical and durability properties were best at 30% GGBS contentand 0.35 water/binder ratio. The DMDA for mix proportion adopted for RAC contributed sig-nificantly to improving its properties when compared to NAC, especially at the optimumobserved RAC mix with compressive strength of 52 MPa. Also, the mix demonstrated goodpermeability resistance in terms of chloride-ion ingress and capillary water absorption.
38
Wen, Chao. "Bounding Surface Approach to the Fatigue Modeling of Engineering Materials with Applications to Woven Fabric Composites and Concrete." Diss., North Dakota State University, 2011. https://hdl.handle.net/10365/28843.
Full textAbstract:
It has been known that the nucleation and growth of cracks and defects dominate the fatigue damage process in brittle or quasi-brittle materials, such as woven fabric composites and concrete. The behaviors of these materials under multiaxial tensile or compression fatigue loading conditions are quite complex, necessitating a unified approach based on principles of mechanics and thermodynamics that offers good predictive capabilities while maintaining simplicity for robust engineering calculations. A unified approach has been proposed in this dissertation to simulate the change of mechanical properties of the woven fabric composite and steel fiber reinforced concrete under uniaxial and biaxial fatigue loading. The boundary surface theory is used to describe the effect of biaxial fatigue loading. A fourth-order response tensor is used to reflect the high directionality of the damage development, and a second-order response tensor is used to describe the evolution of inelastic deformation due to damage. A direction function is used to capture the strength anisotropic property of the woven fabric composite. The comparisons between model prediction results and experimental data show the good prediction capability of models proposed in this dissertation.
39
Souza, Andréa Resende. "Retração em concreto autoadensável: contribuição de produtos mitigadores." Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/2330.
Full textAbstract:
CAPESO concreto autoadensável (CAA) apresenta-se como o concreto do futuro por aumentar o rendimento e reduzir barulho e risco de acidentes nas obras, além de possibilitar a execução de elementos esbeltos ou com elevada taxa de armadura, além da eliminação do processo de adensamento do concreto. No entanto, por apresentar um alto teor de pasta cimento, e refinamento da rede porosa existe o aumento das forças capilares e, por consequência, elevação das mudanças volumétricas presentes na matriz cimentícias, oriundas do processo de retração por hidratação e de secagem dessa matriz. Desta forma, esse trabalho busca avaliar a eficácia de diferentes soluções mitigadoras de retração (autógena e por secagem), em misturas de CAA, sendo utilizado como adições ao estudo: aditivo redutor de retração (SRA), adição compensadora de retração do tipo-S (CSA), fibra polimérica de polipropileno (FP) e um tipo de polímero superabsorvente a base de poliacrilato de potássio (SAP). Com o objetivo de analisar o desempenho dessas adições foram realizados os ensaios de retração, conforme NM 131 (1997) e avaliação da influência dessas adições nas propriedades no estado fresco e endurecido do CAA. As misturas de CAA foram confeccionadas com três diferentes cimentos (CP V ARI, CP II-Z e CP II-E) em combinação com três teores de SRA (1%, 1,5% e 2%), com três teores de CSA (3%, 5% e 7%), com três teores de FP (0,05%, 0,10% e 0,15%) e com três teores de SPA (0,10%, 0,15% e 0,20%) totalizando 39 amostras. Os resultados de ANOVA mostraram que tanto o tipo de cimento, quanto o tipo da adição influenciam significativamente as propriedades avaliadas nesse estudo, tanto as do estado fresco quanto endurecido. Para mitigar a retração autógena e hidráulica foi verificado a influência do tipo de cimento e adição, onde o emprego de CP II-Z reduz a retração entre os cimentos para as misturas de controle, e a adição de 7% de CSA resultam em menores retrações para todos os concretos. Com os resultados obtidos foi verificado que definir o melhor tipo de adição mitigadora da retração ao CAA é um processo complexo, pois exige, além da análise em laboratório, análise da sua aplicação em campo. Ressalta-se que as adições são, em diferentes proporções, capazes de afetar em diferentes ruas, a retração e as propriedades mecânicas do concreto. Deve-se também ressaltar, que tanto a habilidade passante, quanto a perda de trabalhabilidade, são também afetadas pela escolha do tipo de cimento, tipo de adição e teor empregado. Entretanto, em que pese o fato da ocorrência dessas mudanças, foi possível constatar que os concretos produzidos com cimento CP V ARI e fibra polimérica, nos teores de 0,05%, ou com aditivo compensador de retração, no teor de 7%, apresentam-se como potencialmente aplicáveis em várias utilizações.
Self-compacting concrete (CAA) is the concrete of the future for increasing the performance and reducing noise and risk of accidents in the works, besides allowing the execution of slender elements or with a high rate of reinforcement, besides the elimination of the densification process The concrete. However, due to the high content of cement paste and the porous network refinement, there is an increase in the capillary forces and, consequently, increase of the volumetric changes present in the cement matrix, resulting from the retraction process by hydration and drying of the matrix. In this way, this work seeks to evaluate the effectiveness of different retraction mitigation solutions (autogenous and by drying), in CAA mixtures, being used as additions to the study: additive retraction reducer (SRA), compensatory addition of Stype retraction (CSA), polypropylene polymer fiber (FP) and a type of superabsorbent polymer based on potassium polyacrylate (SAP). To analyze the performance of these additions, the retraction tests were performed according to NM 131 (1997) and evaluation of the influence of these additions on the fresh and hardened CAA properties. The CAA mixtures were made with three different cements (CP V ARI, CP II-Z and CP II-E) in combination with three contents of RAS (1%, 1,5% and 2%), with three levels of CSA (3%, 5% and 7%), with three levels of PF (0.05%, 0.10% and 0.15%) and three SPA contents (0.10%, 0.15% and 0.20%) totaling 39 samples. The results of ANOVA showed that both the type of cement and the type of addition significantly influence the properties evaluated in this study, both fresh and hardened. In order to mitigate the autogenous and hydraulic retraction, the influence of cement type and addition was verified, where the use of CP II-Z reduces the retraction between the cements for the control mixtures, and the addition of 7% of CSA results in smaller retractions For all concrete. With the results obtained, it was verified that defining the best type of addition mitigation of retraction to the CAA is a complex process, since it requires, besides the analysis in the laboratory, analysis of its application in the field. It should be noted that the additions are, in different proportions, able to affect in different streets, the retraction and the mechanical properties of the concrete. It should also be noted that both the throughput and the loss of workability are also affected by the choice of cement type, type of addition and content employed. However, in spite of the fact of the occurrence of these changes, it was possible to verify that the concretes produced with cement CP V ARI and polymer fiber, in the contents of 0.05%, or with compensating additive of retraction, in the content of 7%, present Themselves as potentially applicable in various uses.
40
Schaefer, Carolyn (Carolyn E. ). "Irradiated recycled plastic as a concrete additive for improved chemo-mechanical properties in hardened cement pastes." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/114051.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Page 37 blank. Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 33-36).
Portland cement based concrete production contributes heavily to greenhouse gas emissions. Thus a need exists for the development of durable and sustainable concrete with a lower carbon footprint. This can be achieved when Portland cement is partially replaced with another material without compromising the concrete's strength. The use of waste plastics in concrete has been explored as a means of improving concrete's mechanical properties while also providing an efficient way to both re-purpose waste plastic and partially displace cement for the purpose of reducing carbon emissions. This replacement, however, typically comes with a sacrifice of compressive strength. This work discusses the design for and progress toward a high-strength concrete with a dense cementious matrix that contains an irradiated plastic additive. Cement samples containing various combinations of cement binder and plastic content were prepared; compressive strength tests showed that for all cement binder types, the addition of high dose irradiated plastic resulted in increased compressive strength as compared to the strengths achieved by samples with regular, non-irradiated plastic. This suggests that irradiating plastic at a high dose is a viable potential solution for gaining some of the strength back that is lost when plastic is added to concrete. To assess the internal structure of the samples and gain some insight into what aspects of their chemical compositions' contributed to the observed strength differences, a microstructural analysis -- consisting of XRD, SEM, and X-ray microtomography -- was performed. XRD analysis showed that various differences in C-S-H and C-A-S-H phase formation from the addition of both irradiated plastic and mineral additives helped to form high-density phases that contributed to higher relative strengths. BSE analysis showed that an increased alumina content among fly ash samples helped to form the high-density phases that contributed to higher relative strength among the fly ash samples, as evidenced through a ternary phase diagram. X-ray microtomography showed that the addition of high dose irradiated plastic consistently contributed to a decrease in segmented porosity, indicating that irradiated plastic may have acted as a pore-blocking agent. The results presented clearly show the benefit of using irradiated plastic as a concrete additive for improved compressive strength. By partially replacing Portland cement with a repurposed waste material, this design, when scaled to the level of mass concrete production, could contribute to reduced carbon emissions and provide a long-term solution for waste plastic storage.
by Carolyn Schaefer.
S.B.
41
Ameli, Mehran. "Investigating the behaviour of FRP strengthened reinforced concrete beams under torsion /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18734.pdf.
Full text
42
Bozkurt, Emrah Tanoğlu Metin. "Mechanical and thermal properties of non-crimp glass fiber reinforced composites with silicate nanoparticule modified epoxy matrix/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/makinamuh/T000517.pdf.
Full textAbstract:
Thesis (Master)--İzmir Institute of Technology, İzmir, 2006Keywords: polymer composites, Nanoparticles, glass fiber, mechanical properties, thermal properties. Includes bibliographical references (leaves 75-79).
43
Acosta, Urrea Fernando [Verfasser]. "Influence of elevated temperatures up to 100 °C on the mechanical properties of concrete / Fernando Acosta Urrea." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.
Full text
44
Amirrasouli, Benyamin. "Mechanical properties of low density fibre-reinforced cellular concrete and its energy absorption potential against air blast." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-properties-of-low-density-fibrereinforced-cellular-concrete-and-its-energy-absorption-potential-against-air-blast(a8457a33-c479-4db9-adbc-579599783bc9).html.
Full textAbstract:
The scope of this study is to establish extensive material tests to determine the mechanical properties of cellular concrete and evaluate its potential as energy absorption material against air blast load. This study includes a literature review of existing studies on cellular concrete, proportioning, and its mechanical properties, together with studies on the properties and application of other foams such as aluminium and polymer foams. It is concluded that, unlike other foam materials, there is a lack of systematic studies on the mechanical properties of cellular concrete especially for densities less than 1000 kg/m3. The survey also reviewed the existence of materials being used as a sacrificial layer against air blast load, together with the analytical models proposed to determine the parameters required to design a cladding system. As a result it was found that cellular concrete can maintain most of the properties of the cladding materials and can be applied as a new sacrificial layer against the blast load. Extensive material tests are carried out to characterise the effect of ingredients and density on material properties of cellular concrete. Based on the experimental results, an empirical model is proposed which determines the plateau and densification regime of nominal stress-strain curve of the cellular concrete with different densities. The penetration resistance of cellular concrete with different densities under truncated, conical, flat and hemi-spherical solid indenters are studied experimental. By determining the deformation mechanism of cellular concrete under indentation with application of an X-Ray tomography image system, an analytical model is proposed to determine the resistance of cellular concrete under penetration of flat indenter. Experimental closed range blast tests are performed with 1kg and 3kg C4 explosive to determine the mitigation potential of cellular concrete against air blast load. Numerical modelling of the experimental blast test is carried out using Ansys LS-DYNA to evaluate the feasibility of the numerical modelling techniques to predict the response of cellular concrete against air blast load.
45
Baccin, Antonio Guilherme Canhassi. "Fundamentos do concreto de alto desempenho e sua aplicação no projeto de pilares." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-14122017-152756/.
Full textAbstract:
Grandes vantagens econômicas e estruturais são obtidas com a utilização do concreto de alto desempenho (CAD), tais como: redução das seções dos elementos, baixa porosidade e permeabilidade, elevada resistência ao desgaste e menor custo de manutenção. Isto tem contribuído para a crescente aplicação do concreto de alto desempenho, o qual está sendo empregado em vários países, entre os quais: EUA, Noruega, Canadá, Inglaterra, França e Japão. No Brasil, o concreto de alto desempenho já está sendo utilizado em diferentes tipos de obras, apesar de não existir ainda uma norma específica. Os procedimentos de cálculo e critérios de projetos, recomendados pela Norma Brasileira, ainda estão baseados em resultados experimentais de concretos de baixa resistência. Em vista disso, este trabalho apresenta um estudo teórico sobre os materiais constituintes do CAD, as quantidades que devem ser empregadas nos concretos e as diferenças existentes na forma de produção e no controle de qualidade. São também estudadas algumas propriedades mecânicas do concreto de alto desempenho, como resistência à compressão, resistência à tração, módulo de deformação longitudinal, curva tensão-deformação e coeficiente de Poisson. Várias recomendações são indicadas para projeto de pilares, como taxa mínima de armadura longitudinal e transversal, resistência ao escoamento, espaçamento e configuração da armadura transversal, a fim de se garantir apropriada ductilidade de pilares de concreto de alto desempenho. E por último, têm-se exemplos de dimensionamento de pilares, com base nos procedimentos indicados na norma americana ACI 318-89 e na britânica BS 8110.Many advantages not only an economical but also from a structural point of view are obtained when using the high-performance concrete (HPC), such as: reduction of element section, low porosity and permeability, high wearing resistance and less cost of maintenance. This has contributed to a growing use of HPC in several countries, among them: USA, Norway, Canada, England, France and Japan. In Brazil, HPC is being used in different kinds of construction work, although there are no existing standards yet. Procedures of the sizing and desing criteria, recommended by Brazilian standards, are still based in experimental results obtained with low-strength concretes. Given that, this paper presents a theoretical study on material components of HPC, the amount to be employed on preparation of those concretes and the existing differences on ways of production and quality control. Also studied are some mechanical properties of HPC, such as: compression strength, tension strength, elasticity modulus, strain-strength curve and Poisson\'s ratio. Several recommendation are pointed out for columns design, such as: minimun rate of both longitudinal and transverse reinforcements, yielding strength, spacing and lay out of transversal reinforcement to provide adequate ductility of columns made with HPC. Lastly examples of design of columns based on American standard ACI 318-89 and British standard BS 8110 are given.
46
Trussoni, Matthew. "Fracture Properties of Concrete Containing Expanded Polystyrene Aggregate Replacement." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/285.
Full textAbstract:
Fracture mechanics is applied to study the behavior of concrete containing expanded polystyrene (EPS) aggregate replacement. The EPS replaces a portion of the normal weight fine aggregate. Previous research has shown EPS aggregate replacement changes the failure mode in compression from a typical instantaneous failure, as in normal weight concrete (NWC), to a more gradual dissipation of load carrying capacity. This behavior is investigated through the use of fracture mechanics. The fracture energy, critical stress intensity factor and characteristic length of EPS concrete, NWC and fiber reinforced concrete (FRC) are experimentally determined. The two types of tests used to study these properties are the three point bending test recommended by the RILEM technical committee and a wedge splitting test developed recently. The conclusions derived from this research demonstrate that EPS aggregate replacement increases the size of the fracture process zone in front of the crack tip. This increase in size changes the failure mode of concrete allowing it to maintain load after reaching peak load and absorb more energy during the fracture process.
47
Vieira, Geilma Lima. "Influência da microfissuração causada por carregamento precoce nas propriedades mecânicas de concretos produzidos com diferentes tipos de cimento." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/18291.
Full textAbstract:
No Brasil, o processo construtivo como um todo está modificado, assim como o cálculo estrutural e as técnicas gerenciais de construção. Algumas empresas que visam competitividade no mercado buscam soluções para aumentar a velocidade de suas obras, como redução do tempo de execução da estrutura, redução do período de escoramento e antecipação das alvenarias. A retirada antecipada do escoramento submete a estrutura de concreto a um carregamento precoce, sem que haja tempo de ocorrerem todas as reações de hidratação do cimento, podendo desencadear um processo de microfissuração. Dessa forma, o presente estudo avaliou o comportamento das propriedades mecânicas de concretos produzidos com quatro diferentes tipos de cimento (CPV ARI, CPV ARI RS, CPIV RS, CPII Z), quando submetidos a um carregamento precoce de compressão. Foram avaliados resultados de resistência à compressão, resistência à tração por compressão diametral, módulo de elasticidade, velocidade de onda ultra-sônica, condições de cura e ensaios de microscopia eletrônica de varredura. Procurou-se analisar o efeito de diferentes níveis de resistências com a produção de concretos com relações água/cimento de 0,35, 0,50 e 0,70, quando submetidos a um carregamento precoce em diferentes idades (1, 3 e 7 dias) e diferentes percentuais de carregamento (0%, 25%, 50% e 75%). Aos 28 dias foram ensaiados em suas propriedades especificadas. Os resultados mostraram que à medida que aumenta a idade de carregamento, as propriedades mecânicas são melhoradas para todos os cimentos. Por outro lado, quando se aplica os percentuais de pré-carregamento a resistência à compressão tende a aumentar, principalmente para o cimento CPV ARI. A análise de microscopia possibilitou a visualização de microfissuras causadas pelo pré-carregamento, assim como a recuperação das mesmas. Em relação aos outros cimentos foi observada uma queda nos valores de resistência à tração e no módulo de elasticidade.In Brazil the building process as a role is modified, as well as structural design and building management techniques. The companies that aim competitiveness in the market are in search of solutions to increase the speed of their constructions, like reduction of structure execution time, reduction of support time and anticipated masonry execution. The anticipated remove of support submits the concrete structure to a premature load, carrying damage in cement hydration reaction, can unleash microcracking process. In this way, the present study evaluated the mechanical properties behavior of concretes produced with four different cements types (CPV ARI, CPV ARI RS, CPIV RS, CP IIZ), when submitted to premature compression load. The analysis included evaluation of the results of compressive strength, split tensile strength, modulus of elasticity, ultrasonic pulse velocity, cure conditions and scanning electron microscopic. The effect from different strengths levels with 0.35, 0.50 and 0.70 water/cement ratio, when submitted to a premature load in different ages (1, 3 and 7 days) and different percents of load (0%, 25%, 50% and 75% from rupture load) were analyzed. At The concrete with the age of 28 days was submitted to tests in order to specify its properties. The results showed that the mechanical properties of all cements improve as the age of load increases. In the other hand, when the preload area applied, the compressive strength tends to increase, mainly to CPV ARI cement. The microscopy analysis makes possibly the visualization of microcracking caused by preload, as well the recovering themselves. In the other cements were observed a small decrease in tensile strength and modulus of elasticity values.
48
CHEN, KING KONG, and 陳金剛. "Mechanical properties of self-consolidating concrete." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/94820208451941696512.
Full textAbstract:
碩士國立中興大學
土木工程學系
91
Abstract The purpose of this study is to investigate the mechanical properties of self-consolidating concrete and normal concrete. A total of one hundred and thirty -four specimens were made in this study, seventy four were self-consolidating concrete and the rest were normal concrete. The results show that : 1. The strength development of normal concrete is higher than that of self-consolidating concrete. The strength development at 3 or 7 days of normal concrete is 2-3% higher than that of self-consolidating concrete. 2. The elastic modulus of normal concrete is lower than that of self-consolidating concrete. 3. The stress-strain curves of normal concrete are lower than that of self-consolidating concrete.
49
Juang, Yi-Ping, and 莊依萍. "The Mechanical Properties of Recycled Aggregate Concrete." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/23215442252642248211.
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
98
Recycling aggregated concrete is an increasingly important practice due to the overall goal of environmental protection. To enhance the use of recycled aggregate concrete (RAC) in order to enable energy conservation and sustainable development, the complete specifications of RAC must be determined. The key issue in reusing waste concrete is the quality of the recycled aggregate, which is determined according to its absorption of water. This study investigates the effects of brick and tile content in recycled aggregate on the mechanical properties of RAC. The results indicate that compared with normal concrete (NC), the slump of RAC significantly decreased, but the brick content of recycled aggregate only induced a slight change in slump. The test results showed that the unit weight of RAC ranged from 2206 kg/m3-2285 kg/m3, which was less than that of NC. The air content of RAC ranged from 1.1%-2%, which was higher than NC. The compressive strength of RAC decreased 15~30% compared with NC, but brick content had no obvious effect on the compressive strength of RAC. The flexural strength of RAC decreased 10-25% compared with normal concrete. The flexural strength of recycled concrete made from washed aggregates was better than that made from unwashed aggregates. With a low water-to-cement ratio, the water absorption of recycled aggregate had an obvious effect on recycled aggregate concrete, but brick content had no obvious effect on the flexural strength of RAC. Adding pozzolanic materials such as fly ash and slag in RAC could not improve the carbonation depth. Apparent chloride diffusion coefficient of NC is higher than RAC.
50
Shu, Bing-Kun, and 許炳崑. "Mechanical properties of Polypropylene Fiber Lightweight Concrete." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/55708906960735239420.
Full textAbstract:
碩士萬能科技大學
材料科學與工程研究所
101
Polypropylene fiber concrete has several good effective, such as reducing cracks, improve long-term performance, deformation capacity and durability on the construction engineering. Therefore, it has been subject to a wide range of applications in the military, transportation, construction and other projects. However, the studies of polypropylene fiber concrete are focus on the improvements of cracks an strength. And the references on the studies of polypropylene fiber utilized in the construction performance and mechanical properties of lightweight concrete were deficiency. In the study, the polypropylene fiber concretes consisted of lightweight aggregate which resulted from the reservoir sludge sintering under a high temperature, concrete and polypropylene fiber. The relationship between the mechanic properties and age of raising for of several compositions of polypropylene fiber concrete inhere are investigated by three ratios of water-cement (W/C) to estimate the optimization add specifications and content of polypropylene fiber in the concrete. Furthermore, the factors of the changes of polypropylene fiber concrete are also verified by SEM and XRD. The results showed that the mechanic strength under the ages of raise has no improve for the w/c=0.41. As the w/c=0.48 and 0.57, the mechanic strength is increased as the under the ages of raise, which is result from the polypropylene fiber lead the crystal of CH to transform the C-S-H gel and the bond strength is also improvement for the mechanic strength of polypropylene fiber concrete.