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Artykuły w czasopismach na temat "Air entrainment in cement and cement mortars"
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Miera, Patrycja. "Air Content in Fresh Air-Entraining Cement Mortars". IOP Conference Series: Materials Science and Engineering 1203, nr 3 (1.11.2021): 032016. http://dx.doi.org/10.1088/1757-899x/1203/3/032016.
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Abstract The durability of a cement composite is the most important criterion for assessing this material. However, due to the durability of the cement composite, its frost resistance is an important property. In order to ensure concrete frost resistance, the European standard PN-EN 206-1: 2013 requires its aeration at the level of 4 - 7%. The Committee 201 of the American Concrete Institute (ACI) also requires the use of an air-entraining admixture in concretes exposed to frost damage. The amount of air-entraining admixture is significantly influenced by the composition of the cement used. In order to minimize the problems with obtaining frostresistant concrete, an attempt was made to create air-entraining cements. This article presents the effect of the amount and type of dosing of air-entraining admixtures (natural and synthetic) on the air content in fresh air-entraining cement mortars. The test cements used also differed in the production method: joint mixing of components and joint grinding of components. Based on the research, a lot of valuable information was obtained related to the influence of the preparation of air-entraining cements on the air content in the mortar, e.g. mortars with mixed cement with natural air-entraining admixture have a higher air content. The air content is higher in the cement co-ground with natural air-entraining admixture. A synthetic air entraining admixture added separately to mixed cements with silica fly ash and ground granulated blast furnace slag increases air entrainment in mortars. The synthetic air-entraining admixture added separately to co-milled cements causes an increase in air entrainment in the mortars, except for those containing cement with ground granular blast furnace slag.
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Tian, Ye, Zong Jin Li, Hong Yan Ma, Xian Yu Jin i Nan Guo Jin. "Physical and Chemical Influence of Polyacrylate Latex on Cement Mortars". Advanced Materials Research 261-263 (maj 2011): 807–11. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.807.
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In this research, the physical and chemical influence of polyacrylate (PA) latex on cement-based materials were studied using polymer modified mortars with polymer/cement (P/C) ratios of 0%, 5% and 10%. Physically, the mechanical performance of PA latex modified mortars was investigated with compression toughness energy and bending strength. Further more, a comparison of the pore structure and porosity between PA latex modified and unmodified mortars was conducted. The chemical reactions between PA polymer and cement hydrates were clarified with thermogravimetric (TG) analysis. It can be concluded from this research that PA polymer can refine the pore structure of cement mortars and link the cement hydration products together chemically. While, at the same time, PA latex addition can cause air entrainment which will weaken the physical behavior of cement mortars. So there is an optimum P/C ratio to achieve the best mechanical properties. And in this research, the optimum P/C ratio is 5%.
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Riyazi, Siamak, John T. Kevern i Matt Mulheron. "Super absorbent polymers (SAPs) as physical air entrainment in cement mortars". Construction and Building Materials 147 (sierpień 2017): 669–76. http://dx.doi.org/10.1016/j.conbuildmat.2017.05.001.
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Tebbal, Nadia, Zine El Abidine Rahmouni i Lamis Rabiaa Chadi. "Study of the Influence of an Air-Entraining Agent on the Rheology of Motars". MATEC Web of Conferences 149 (2018): 01054. http://dx.doi.org/10.1051/matecconf/201814901054.
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The objective of this study is to analyze the effect of the air entrainment on the fresh rheological properties as well as on the compressive mechanical resistances of the mortars. The hardened concrete contains a certain amount of randomly spread air, coming either from a drive during kneading or from the evaporation of the mixing water. The air quantity is in the order of 20 l / m3, ie 2% of the volume. However, the presence of a large volume of air bubbles causes the mechanical resistances to fall in compression. On the other hand, the use of air entrainment could improve the rheological properties of fresh concrete. Experimental studies have been carried out to study the effect of air entrainment on compressive strength, density and ingredients of fresh concrete mix. During all the study, water cement ratio (w/c) was maintained constant at 0.5. The results have shown substantial decreasing in water and mortar density followed with decreasing in compressive strength of mortar. The results of this study has given more promising to use it as a guide for mortar mix design to choose the most appropriate concrete mix design economically.
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Sun, Zhen Ping, Dan Mei Ye, Le Feng Fu, Bo Cun Zheng, Zhong Jun Feng i Ming Chen. "Properties of Polyacrylic Ester Latex Modified Cement Mortar". Advanced Materials Research 687 (kwiecień 2013): 166–74. http://dx.doi.org/10.4028/www.scientific.net/amr.687.166.
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The water reducing performance, retarding effect, air entrainment, flexural and compressive strength of polyacrylic ester (PAE) latex modified cement mortar were investigated with fixed flow values. The research shows that PAE latex has water-reducing performance. The amount of water used in modified cement mortar decreases with increasing dosage of PAE latex. Because of the retarding effect, PAE latex delays the hydration process of cement. PAE latex has a strong effect of air entraining, and the air content of fresh mortar can be controlled by suitable dosage of defoamer. With the same air content of fresh mortar, PAE latex can obviously improve the flexural strength of cement mortar, and has no adverse effect on its compressive strength.
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Zhao, Ruohong, Yubin Weng, Christopher Tuan i An Xu. "The Influence of Water/Cement Ratio and Air Entrainment on the Electric Resistivity of Ionically Conductive Mortar". Materials 12, nr 7 (5.04.2019): 1125. http://dx.doi.org/10.3390/ma12071125.
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Ionically-conductive mortar can be used for indoor radiant heating partition walls. In these applications, mortar blocks are soaked in electrolyte solutions of CuSO4. The surfaces of the block are coated with sealant and epoxy resin afterwards to prevent evaporation. The mortar block becomes a heating element due to ionic conduction if a voltage is applied to the electrodes in the block. Its electrical conductivity depends on the dispersion of the electrolyte, and hence on the porosity of the mortar. The test specimens in this study were divided into four groups according to the different air entrainment agents, including aluminum powder and hydrogen peroxide as well as two air-entraining agents, SJ-2 and K12. Each group was manufactured with water/cement ratios in the range of 0.5 to 0.9. The test results showed that the conductivity of the mortar was strongly influenced by the air-entrainment and the water cement ratios. The volumetric electric resistivity and the associated microstructures of the mortar were investigated. The test results showed that the specimens made with aluminum powder and a water–cement ratio of 0.65–0.75 had high porosity. The porosity of those specimens was further increased by adding two different air-entraining agents. The specimens with aluminum powder and SJ-2, along with a water–cement ratio of 0.7 appeared to be the optimum mixture. Its resistivity was 19.37 Ω·m at 28 days under 25.31% porosity. The experimental results indicate that an ionically-conductive mortar can be produced by combining different air-entrainment agents with variable water-cement ratios to meet a specified electrical heating requirement.
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Wang, Rui, Lei Li, Wei Wang, Hong Song Wang, Yong Jing Jiang i Da Pu Shen. "Influences and Properties of Mortar Modified by Waterborne Polyurethane Latexes". Advanced Materials Research 1129 (listopad 2015): 345–52. http://dx.doi.org/10.4028/www.scientific.net/amr.1129.345.
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Two waterborne polyurethane latexes with different tensile strength were employed to modify mortar and the properties of mortar including air entrainment, setting behavior, compressive and flexural strength were investigated. The results show that curing methods, polymer-cement ratio and water-cement ratio have a significant impact on the compressive and flexural strength. The strength of mortar increased under dry curing condition in the range of the polymer-cement ratio from 0.005 to 0.05 (by weight) at water-cement ratio of 0.5. The hydration of the cement containing waterborne polyurethane latexes was not affected and no visible film was found in SEM images.
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Zuo, Shenghao, Qiang Yuan, Tingjie Huang, Zan Wang, Kai Zhang i Jing Liu. "Rheology and air entrainment of fresh Portland cement mortars in simulated low air pressure environments". Cement and Concrete Composites 135 (styczeń 2023): 104848. http://dx.doi.org/10.1016/j.cemconcomp.2022.104848.
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Łazniewska-Piekarczyk, Beata, i Janusz Szwabowski. "THE INFLUENCE OF THE TYPE OF ANTI-FOAMING ADMIXTURE AND SUPERPLASTICIZER ON THE PROPERTIES OF SELF-COMPACTING MORTAR AND CONCRETE". Journal of Civil Engineering and Management 18, nr 3 (29.06.2012): 408–15. http://dx.doi.org/10.3846/13923730.2012.698908.
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To prevent excessive air entrainment, superplasticizers (SPs) should not only be compatible with cement, but also should not create the air-entraining effect in mortar. In order to counteract excessive air entrainment, anti-foaming admixtures (AFAs) can be used to prevent the formation of air bubbles. This paper investigates the influence of the type, amount and time of introduction of AFAs on air-entrainment, rheological properties and workability loss of self-compacting mortar. The research results prove that AFAs decrease air-content in mortar. Mortar containing an AFA does not undergo segregation, as is the case with mortars of a similar degree of fluidity with no AFA and incorporating an SP only. Moreover, mortar with an AFA keeps initial consistency for longer in comparison to mortar with a SP only. The properties of hardened mortar mixes are also investigated. The research results show that AFAs do not have a significant influence on the compressive strength of mortar mixtures. The compressive strength of mortar mixtures incorporating an AFA is similar to mortar with a non-air-entraining SP. Moreover, AFAs increase significantly the flexural strength of mortar. In most cases, AFAs do not decrease the absorbability of mortar. Only two types of AFAs increase slightly the absorbability of mortar. In order to explain this phenomenon, a research was performed investigating the porosity structure according to the EN 480-11 (1999) and SEM analyses of two types of self-compacting concrete (SCC): one made of mortar with an AFA and the other without AFA. The freeze-proof resistance of SCC (made of the same mortar mixes) was also investigated according to PN-88/B-06250 (2003). The results show that the type of AFA and SP significantly influences porosity characteristics and frost-resistance of SCC.
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Chen, Xin, Xu Liu, Bo Tian, Yong Ge i Lihui Li. "Effect of Low Atmospheric Pressure on Air Entrainment in Cement-Based Materials: An On-Site Experimental Study at Different Elevations". Materials 13, nr 18 (8.09.2020): 3975. http://dx.doi.org/10.3390/ma13183975.
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The efficiency and stability of air entrainment in concrete are sometimes found to be weaker at higher elevation. This phenomenon was attributed to the low atmospheric pressure by many researchers, however, the level of influence of atmospheric pressure on concrete air content dramatically varied among different studies. In order to clarify the effect of low atmospheric pressure on air entrainment in cement-based materials, an on-site experimental study was conducted with a rigorous control of irrelevant variables. The study focused on the air-entraining efficiency in cement paste, mortar, and concrete prepared in both low and standard atmospheric pressures. The air bubble stability in fresh mortar and air void characteristics of hardened mortar in different atmospheric pressures were also included. In the study, little effect of low atmospheric pressure on the air-entraining efficiency and air bubble stability in mortar with studied air-entraining agents (AEAs) was found. The air void characteristics were found to be similar between mortar with SJ-2 or 303R type AEAs prepared in different atmospheric pressures. Concrete with either SJ-2 or 303R type AEA prepared in low atmospheric pressure presented a satisfactory air content. These conclusions indicate that it is not necessary to worry excessively about the potentially adverse effect of atmospheric pressure on the frost resistance of concrete if a suitable AEA is applied. Additionally, a supplementary mortar study found that the low temperature of raw materials stored at high elevation would significantly weaken the air entrainment, reminding that potential causes in addition to low atmospheric pressure should also be taken seriously.
Rozprawy doktorskie na temat "Air entrainment in cement and cement mortars"
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Kmack, Richard Matthew. "Characterization of air voids in fresh cement paste through ultrasonic nondestructive testing". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24794.
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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jacobs, Laurence; Committee Co-Chair: Kurtis, Kimberly; Committee Member: DesRoches, Reginald.
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Lima, Marco Ant?nio Batista de. "Formula??o e caracteriza??o de pastas espumadas por incorpora??o de ar e estabilizantes minerais". Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12969.
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Previous issue date: 2011-02-08Cementing operations may occur at various stages of the life cycle of an oil well since its construction until its definitive abandonment. There are some situations in which the interest zones are depleted or have low fracture pressure. In such cases, the adoption of lowdensity cement slurries is an efficient solution. To this end, there are basically three ways to reduce the density of cement slurries: using microspheres, water extending additives or foamed cement. The objective of this study is to formulate, to study and to characterize lowdensity foamed cement, using an air entrainment surfactant with vermiculite or diatomite as water extenders and stabilizers. The methodology consists on preparation and evaluation of the slurries under the American Petroleum Institute (API) and the Brazilian Association of Technical Standards (ABNT) guidelines. Based on calculated densities between 13 and 15 ppg (1.559 and 1.799 g/cm3), the slurries were prepared with fixed surfactant concentration, varying the concentrations of vermiculite and diatomite and were compared with the base slurries. The results of plastic viscosity, yield point and gel strength and the compressive strength for 24 h showed that the slurries presented suitable rheology and mechanical strength for cementing operations in oil wells, and had their densities reduced between 8.40 and 11.89 ppg (1.007 and 1.426 g/cm3). The conclusion is that is possible, under atmospheric conditions, to obtain light weighted foamed cement slurries with satisfactory rheological and mechanical properties by means of air entrainment and mineral additions with extenders and stabilizers effects. The slurries have great potential for cementing operations; applicability in deep wells, in low fracture gradient formations and in depleted zones and bring cost savings by reducing the cementing consumption
As opera??es de cimenta??o podem ocorrer em diversas etapas do ciclo de vida de um po?o, desde a sua constru??o at? seu abandono definitivo. H? situa??es em que as zonas de interesse se apresentam depletadas ou com baixa press?o de fratura. Nesses casos, a ado??o de pastas cimentantes de baixa densidade constitui solu??o eficiente. Para tanto, h? basicamente tr?s maneiras de reduzir a densidade de pastas de cimento: usando microesferas, aditivos estendedores de ?gua ou pastas espumadas. O objetivo deste trabalho ? formular, estudar e caracterizar pastas cimentantes espumadas de baixa densidade, utilizando um surfactante incorporador de ar juntamente com adi??es de vermiculita ou diatomita como estendedores e estabilizantes. A metodologia do trabalho consiste na prepara??o e avalia??o das pastas por meio de procedimentos adotados pelo American Petroleum Institute (API) e pela Associa??o Brasileira de Normas T?cnicas (ABNT). Partindo de densidades calculadas entre 13 e 15 lb/gal (1,559 e 1,799 g/cm3), as pastas foram preparadas com dosagem fixa do surfactante, variando as concentra??es de vermiculita e diatomita e foram comparadas com pastas base. Os resultados dos ensaios que determinam viscosidade pl?stica, limite de escoamento e for?as g?is, bem como os de resist?ncia ? compress?o para tempos de 24 h mostraram que as pastas apresentaram reologia e resist?ncia mec?nica adequadas para opera??es de cimenta??o em po?os de petr?leo, al?m de terem suas densidades reduzidas entre 8,40 e 11,89 lb/gal (1,007 e 1,426 g/cm3). Conclui-se que ? poss?vel, sob condi??es atmosf?ricas, obter pastas cimentantes espumadas de baixa densidade com propriedades reol?gicas e mec?nicas satisfat?rias, por meio de incorpora??o de ar e adi??es minerais com efeitos estendedores e estabilizantes. As pastas possuem grande potencial para opera??es de cimenta??o, t?m aplicabilidade em po?os profundos, forma??es de baixo gradiente de fratura e zonas depletadas e trazem redu??es de custo pela diminui??o do consumo de cimento
Części książek na temat "Air entrainment in cement and cement mortars"
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Smith, A. S., i R. Givens. "A review of research and experimental findings on the effects of hydrated (air) lime addition to cement-based masonry mortars on the properties of the mortars and associated masonry". W Brick and Block Masonry, 1897–904. CRC Press, 2016. http://dx.doi.org/10.1201/b21889-236.
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Baral, Aniruddha, i Jeffery R. Roesler. "Hydration and Air Entrainment Challenges of High-Volume Fly Ash Concrete Pavement". W 12th International Conference on Concrete Pavements. International Society for Concrete Pavements, 2021. http://dx.doi.org/10.33593/d0owmqk5.
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The goal of high-volume fly ash concrete (HVFAC) is to produce concrete pavements at a lower cost and carbon footprint while maintaining its desired durability. Previous research has demonstrated that the required fresh and hardened concrete properties can be achieved at higher replacement rates of cement with fly ash such as 40%. However, most transportation agencies do not permit more than 30% cement replacement with fly ash primarily because of the potential inconsistencies in early-age properties such as variable air entrainment, delays in setting times, and lower strength gains. In this paper, the heat evolved during hydration of HVFAC are presented with respect to the source of the cement and fly ash, the variability of fly ash from the same source, and addition of nano limestone. Isothermal calorimetry showed longer setting times were dependent on the specific fly ash-cement combination as well as the degree of sulfate imbalance. For this study, HVFAC mixes with class C fly ash had a larger sulfate imbalance than class F fly ash with final setting times 4.5 hours and 1.9 hours longer than straight cement system, respectively. Replacing cement with 10% nano limestone in HVFAC system accelerated the initial set time by 3.2 hours which was much greater than the set time acceleration (1.3 hours) with the replacement of straight cement with 10% nano limestone. The various types of inorganic and organic carbons in fly ash remain a challenge for predicting and maintaining air content but the foam index still offers a rapid and straightforward quality control test with operator variability within ±1 µL AEA/gm fly ash.
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Vyšvařil, Martin, i Patrik Bayer. "Cellulose ethers as water-retaining agents in natural hydraulic lime mortars". W The 13th international scientific conference “Modern Building Materials, Structures and Techniques”. Vilnius Gediminas Technical University, 2019. http://dx.doi.org/10.3846/mbmst.2019.014.
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Cellulose ethers (CEs) are commonly used as viscosity enhancing, water retaining agents in cement-based mortars. Nevertheless, studies about the effect of CEs on the properties of natural hydraulic lime-based mortars (NHL) are absent, although the use of mortars with hydraulic lime is often preferred for renovation purposes. In this study, the behavior of NHL mortars modified by four different CEs is assessed. The fresh state of mortars was characterized by water retention, air content, density a consistency. Hardened mortars were submitted to strength determination, study of pore size distribution, and thermogravimetric analyses. Transport of liquid water in the studied materials was characterized by water absorption coefficient, sorptivity, and liquid water diffusivity. Durability of the prepared mortars was monitored by frost-resistance tests. The results revealed elevated air content and water retention in mortars with increasing dose of CEs resulting in decreased density of fresh mortars. The strengths of modified mortars surpassed the reference ones at age of 180 d despite the fact that the mortars showed higher open porosity and water absorption. Enhanced porosity of mortars resulted in improvement of their frost resistance and faster carbonation. From a practical and economical point of view, the CEs dosage of 0.5% by weight of the binder appears to be sufficient.
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Paiva, Rayane de Lima Moura, Patrícia Brandão Sousa, Camila de Barros Lima Carreira, Adriana Paiva Souza Martins i Romildo Dias Toledo Filho. "Physical, Thermal and Microstructural Characterization of Earth Mortars Stabilized with Incorporating Air Additive". W 4th International Conference on Bio-Based Building Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.211.
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In recent years, the search for non-conventional materials has intensified, aiming to reduce environmental impacts in the civil construction sector as a strategy for more sustainable development. Among these materials, earth mortars are a promising option, as they have technological, economic, and environmental advantages. Due to the absence of literary data on the use of air-incorporating additives (AEA) in earth mortars, the objective of this article is to verify the influence of the incorporation of AEA (0,10, 20, and 40% of the total volume of the mixture) in the mechanical properties (compression strength at 28 days), physical (total water absorption by immersion), thermal, and microstructural (scanning electron microscopy) of the referred mortars. The study was carried out in a stabilized earth mortar, with a 1:3 mass mix proportion (binder: aggregate). The raw materials used were constituted by binders (cement, hydrated lime, fly ash, metakaolinite), aggregates (sand, a coarse fraction of the soil), additives (AEA, calcium chloride, superplasticizer), and water. The water-binder material ratio (a / bm) was fixed at 0.65, and the consumption of binder and aggregate was 461.71 and 1385.12 kg, respectively, per m3 of the mixture. The tests demonstrated that the incorporation of the additive influenced the behavior under compression (strength and stiffness reduction), thermal performance (conductivity reduction), and physical behavior (absorption and voids index´s increases) compared to the mixture without AEA. From the analysis of the results, it was found that the incorporation of air in the mortars led to an increase in porosity, directly influencing the thermal insulation capacity, measured by thermal conductivity. Microstructure changes were observed through SEM images, corroborating the influence of the AEA. Under compression loads, the stiffness reduction decreases the risk of eventual cracking, however, the reduction in strength should be controlled to meet normative limits.
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Pesce, Cecilia, Giovanni Pesce, Marco Molinari i Alan Richardson. "Customising Microstructural and Mineralogical Characteristics of Hydrated Lime Using Biopolymers". W 4th International Conference on Bio-Based Building Materials. Switzerland: Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/www.scientific.net/cta.1.353.
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The study of lime-based systems is vital to the design of new sustainable building materials. Air lime (calcium hydroxide, Ca (OH)2) is a binder that has attracted considerable attention for its ability to capture CO2 from the atmosphere, its low-cost and low-energy production process. Furthermore, Ca (OH)2 is an important phase of hydrated Portland cements, and lime-based mortars have shown high elasticity and the ability of self-healing. The performance of lime-based building materials can be enhanced by the addition of organic compounds that can modify the mineralogy and microstructure of Ca (OH)2. In this study, the effects of four biopolymers including starch, inulin, pectin, and calcium lignosulfonate, on the microstructure and mineralogy of lime have been investigated. Hydrated lime was produced by slaking quicklime in water. Two sets of hydrated lime batches were produced for each polymer: (i) the polymer was previously dissolved in water and subsequently mixed with lime, and (ii) the polymer was added as a dry powder to the already hydrated lime at the end of the slaking process. Characterisation of the batches was performed using scanning electron microscopy, X-ray diffraction and laser diffraction. Results indicate that biopolymers affect the nucleation and growth of Ca (OH)2 crystals. This influences the microstructure and crystal aggregation of hydrated lime in colloidal suspension, which will have important implications on the use of biopolymers in Portland cement applications and in the use of lime as a binder for mortars.
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Kowalska, Danuta, Paweł Iwanowski i Agata Kowalewska. "Determination of Parametres of the Air-Void System in Airfield Pavement Concrete Using Computed Tomography". W Environmental Engineering. VGTU Technika, 2017. http://dx.doi.org/10.3846/enviro.2017.108.
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Immediately after completion airfield pavements begin a gradual deterioration that is attribute to several factors. One of the major elements contribute to airfield pavement deterioration is exposure to the environment (freezingthawing and de-icing salts). Air-voids microstructure in cement-based materials is an important feature related to the freeze-thaw durability of these materials since all the adverse influences are result of potentially harmful ionic fluids and aggressive gas transport through the concrete and the transport properties strongly depend on the morphology of the pores inside the concrete. For revealing the porous microstructure in airfield pavement concrete X-ray tomography method was used. New and advance methodologies have been developed to determine the basic parameters of air entrainment in concrete (total content of the air, specific surface area of the air-voids system, spacing factor and content of micropores) by summing the distances traversed across a given component along a series of regularly spaced lines in one or more planes intersecting the sample. Using the method mentioned above, to meet requirements of PN-EN 480-11 specification (describes procedure for microscopical determination of air voids characteristics in hardened concrete), the original software was applied – AVCT (Air Void by Computed Tomography) computer programme. The specimens for CT testing were cylinders extracted by drilling out from the investigated concrete core or cubic specimen. The CT method does not require any special processing of the surface of tested specimen as opposed the common method according to PN-EN 480-11, by which the properly polished section is a prerequisite for obtaining proper results of air voids characterization. The paper presents the results of the evaluation of air-voids microstructure in concrete conducted with the application of computed tomography method. Exemplary images of distribution and size of air-voids in concrete specimens have been presented. Special attention was paid to obtain effective image resolution.
Raporty organizacyjne na temat "Air entrainment in cement and cement mortars"
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Baral, Aniruddha, Jeffrey Roesler, M. Ley, Shinhyu Kang, Loren Emerson, Zane Lloyd, Braden Boyd i Marllon Cook. High-volume Fly Ash Concrete for Pavements Findings: Volume 1. Illinois Center for Transportation, wrzesień 2021. http://dx.doi.org/10.36501/0197-9191/21-030.
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High-volume fly ash concrete (HVFAC) has improved durability and sustainability properties at a lower cost than conventional concrete, but its early-age properties like strength gain, setting time, and air entrainment can present challenges for application to concrete pavements. This research report helps with the implementation of HVFAC for pavement applications by providing guidelines for HVFAC mix design, testing protocols, and new tools for better quality control of HVFAC properties. Calorimeter tests were performed to evaluate the effects of fly ash sources, cement–fly ash interactions, chemical admixtures, and limestone replacement on the setting times and hydration reaction of HVFAC. To better target the initial air-entraining agent dosage for HVFAC, a calibration curve between air-entraining dosage for achieving 6% air content and fly ash foam index test has been developed. Further, a digital foam index test was developed to make this test more consistent across different labs and operators. For a more rapid prediction of hardened HVFAC properties, such as compressive strength, resistivity, and diffusion coefficient, an oxide-based particle model was developed. An HVFAC field test section was also constructed to demonstrate the implementation of a noncontact ultrasonic device for determining the final set time and ideal time to initiate saw cutting. Additionally, a maturity method was successfully implemented that estimates the in-place compressive strength of HVFAC through wireless thermal sensors. An HVFAC mix design procedure using the tools developed in this project such as the calorimeter test, foam index test, and particle-based model was proposed to assist engineers in implementing HVFAC pavements.
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Baral, Aniruddha, Jeffery Roesler i Junryu Fu. Early-age Properties of High-volume Fly Ash Concrete Mixes for Pavement: Volume 2. Illinois Center for Transportation, wrzesień 2021. http://dx.doi.org/10.36501/0197-9191/21-031.
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High-volume fly ash concrete (HVFAC) is more cost-efficient, sustainable, and durable than conventional concrete. This report presents a state-of-the-art review of HVFAC properties and different fly ash characterization methods. The main challenges identified for HVFAC for pavements are its early-age properties such as air entrainment, setting time, and strength gain, which are the focus of this research. Five fly ash sources in Illinois have been repeatedly characterized through x-ray diffraction, x-ray fluorescence, and laser diffraction over time. The fly ash oxide compositions from the same source but different quarterly samples were overall consistent with most variations observed in SO3 and MgO content. The minerals present in various fly ash sources were similar over multiple quarters, with the mineral content varying. The types of carbon present in the fly ash were also characterized through x-ray photoelectron spectroscopy, loss on ignition, and foam index tests. A new computer vision–based digital foam index test was developed to automatically capture and quantify a video of the foam layer for better operator and laboratory reliability. The heat of hydration and setting times of HVFAC mixes for different cement and fly ash sources as well as chemical admixtures were investigated using an isothermal calorimeter. Class C HVFAC mixes had a higher sulfate imbalance than Class F mixes. The addition of chemical admixtures (both PCE- and lignosulfonate-based) delayed the hydration, with the delay higher for the PCE-based admixture. Both micro- and nano-limestone replacement were successful in accelerating the setting times, with nano-limestone being more effective than micro-limestone. A field test section constructed of HVFAC showed the feasibility and importance of using the noncontact ultrasound device to measure the final setting time as well as determine the saw-cutting time. Moreover, field implementation of the maturity method based on wireless thermal sensors demonstrated its viability for early opening strength, and only a few sensors with pavement depth are needed to estimate the field maturity.