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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.
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Kumar, Shiv. "Effect of Sugar Waste on Cement Concrete". International Journal for Research in Applied Science and Engineering Technology 9, nr 9 (30.09.2021): 1353–60. http://dx.doi.org/10.22214/ijraset.2021.38124.
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Abstract: This investigation deals with the effects of the sugar- waste (Molasses) on the cement concrete. Studies were carried out on a cement paste, the types of different mortar mixes and five types of different concrete mixes, with and without the use of molasses. Molasses is one among the four types of sugar waste and it contains 40-60 percent of total sugar content depending upon types of molasses. While other sugar waste are Bassage, pressed mud and Discharging water containing mud. Among these wastes first two contains 3 percent of sugar and three contains negligible percent of sugar. In the present work molasses was collected sugar mill name. The effects of different dosage level 0, 0.1, 0.25, 0.50, 0.75, 1.00, 2.00, 3.00, 4.00, 5.00 percent of the molasses by weight of cement were studied for standard consistency, setting time, water – reduction behavior and air – entrainment in fresh concrete. The studies were also carried out for 7-day and 28-day compressive strength of the mortar, 7-day, 28-day, 56-day and 91-day compressive strength for five types of concrete mixes, 14-day tensile strength and flexural strength of concrete for the dosage levels 0, 0.10, 0.25, 0.50 percent of molasses by weight of cement. This test results indicates that molasses acts as accelerator upto 0.50 percent dose and then becomes retarder. Also it is slightly a water reducer and air entraining agent. The compressive strength of mortar, concrete, flexural strength and tensile strength of concrete get increased on using 0- 0.50 percent dose of molasses but the most favourable dose is 0.25 percent of molasses by weight of cement. Keywords: Air-entraining admixture, organic materials, microscopic bubbles, cohesion, durability, cavities
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Guo, Jinjun, Yanling Yan, Juan Wang i Yaoqun Xu. "Strength Analysis of Cement Mortar with Carbon Nanotube Dispersion Based on Fractal Dimension of Pore Structure". Fractal and Fractional 6, nr 10 (19.10.2022): 609. http://dx.doi.org/10.3390/fractalfract6100609.
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Carbon nanotubes (CNTs) are considered among the ideal modifiers for cement-based materials. This is because CNTs can be used as a microfiber to compensate for the insufficient toughness of the cement matrix. However, the full dispersion of CNTs in cement paste is difficult to achieve, and the strength of cement material can be severely degraded by the high air-entraining property of CNT dispersion. To analyze the relationship between the gas entrainment by CNT dispersion and mortar strength, this study employed data obtained from strength and micropore structure tests of CNT dispersion-modified mortar. The fractal dimensions of the pore volume and pore surface, as well as the box-counting dimension of the pore structure, were determined according to the box-counting dimension method and Menger sponge model. The relationship between the fractal dimensions of the pore structure and mortar strength was investigated by gray correlation. The results showed that the complexity of the pore structure could be accurately reflected by fractal dimensions. The porosity values of mortar with 0.05% and 0.5% CNT content were 15.5% and 43.26%, respectively. Moreover, the gray correlation between the fractal dimension of the pore structure and strength of the CNT dispersion-modified mortar exceeded 0.95. This indicated that the pore volume distribution, roughness, and irregularity of the pore inner surface were the primary factors influencing the strength of CNT dispersion-modified mortar.
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Zeng, Xiao-Hui, Xu-Li Lan, Hua-Sheng Zhu, Yu-Zhou Ran, Hussaini Abdullahi Umar, Guo-Cui Teng, Jun-Qing Wu, Yun-Xian Zhou, Jie-Bo Peng i Guang-Cheng Long. "Using stirring power curves to investigate the air-entrainment and mechanical properties of cement mortar at low air pressure". Construction and Building Materials 378 (maj 2023): 131142. http://dx.doi.org/10.1016/j.conbuildmat.2023.131142.
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Zhou, Dongliang, Han Yan, Yong Yang, Xin Shu, Lei Chen, Changcheng Li i Qianping Ran. "Investigation of the Effect of Particle Surface Charge and Dispersion Stability on Latex Behavior in Cement Using Non-Ionic and Traditional Latexes". Materials 15, nr 17 (5.09.2022): 6145. http://dx.doi.org/10.3390/ma15176145.
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In this work, a novel total non-ionic polystyrene-polyurethane (PS-PU) composite latex was synthesized with polymerizable polyethylene glycol ether. Contrary to traditional styrene-butyl acrylate latex (St-BA), PS-PU has a smaller size and superior dispersion stability, and it is stable in saturated Ca(OH)2 even after 72 h. In fresh-mixed mortars, PS-PU showed a little adverse effect on workability and insignificant air entrainment, with little defoamer consumption. The retardation effect of PS-PU is also much milder than traditional St-BA. As for strength, PS-PU showed a less adverse effect on early and late age compressive strength, but its effect on flexural strength is not as pronounced as St-BA at high dosages (4% and 6%). The different behavior in cementitious materials between PS-PU and St-BA can be reasoned from their different adsorption behavior and surface charge properties, as the results from characterizations suggest. The non-ionic nature of PS-PU made it less prone to destabilization and adsorption, which turned out as the aforementioned behavior in cementitious systems. The difference can further be ascribed to the difference in their polymeric structure and properties.
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Stenechkina, Kseniya. "The use of superplasticizers in multicomponent concrete mixtures". E3S Web of Conferences 389 (2023): 01032. http://dx.doi.org/10.1051/e3sconf/202338901032.
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In addition to the positive effect of the introduction of a superplasticizer, there are also negative ones: an increase in the period of structure formation, a significant air entrainment and, as a result, a decrease in strength. One of the ways to reduce the negative impact on the structure and properties of concrete composites is the method of preparing a suspension, which consists in first dissolving 10% of the amount of cement in all the mixing water in a concrete mixer for 1-2 minutes. Then load the rest of the cement and aggregate. Preliminary dissolution in water mixing with superplasticizer leads to the formation of a colloidal solution containing an increased amount of micro- and nanoparticles. When a superplasticizer is introduced into a cement-water suspension, particles with a high degree of dispersion are formed, as well as calcium hydrosilicate cristolites with a size of 1-3 nm. This sharply increases the activity of the superplasticizer and, consequently, improves the mobility of the concrete mixture. For example, from P2 to P3, from P3 to P5. This allows to reduce the consumption of the additive by 1.5 - 2 times. It has been established that the superplasticizer can be adsorbed only on hydrate neoplasms. For pre-treatment, it is necessary to use special equipment with high energy consumption such as RPA, fine grinding mills, disintegrators and various activators. Obtaining a cement-water suspension can be carried out in mortar, concrete mixers, in mixers of any type. The concrete mixture consists of cement, crushed stone, sand, water and superplasticizer C-3, determination of the draft of the cone using the Abrams cone, determination of the cubic strength using a hydraulic press in accordance with GOST 10180-2012. It becomes possible to increase the grade in terms of workability as a result of preliminary hydroactivation of the plasticizing additive, which leads to a decrease in its consumption. This method of hydroactivation of superplasticizers for the manufacture of cement concretes can be used to save the consumption of a plasticizing additive.
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de Bem, Diogo Henrique, Daniel Petzold Barbosa Lima i Ronaldo A. Medeiros-Junior. "Effect of chemical admixtures on concrete’s electrical resistivity". International Journal of Building Pathology and Adaptation 36, nr 2 (14.05.2018): 174–87. http://dx.doi.org/10.1108/ijbpa-11-2017-0058.
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PurposeThe purpose of this paper is to verify the influence of superplasticizer and air entrainment admixtures (AEs) in the electrical resistivity of concrete.Design/methodology/approachTen different types of concrete have been studied. Three levels of superplasticizer and air AEs have been used (0.20, 0.35 and 0.50 per cent). Concrete samples were cast and the electrical resistivity was monitored at the ages of 28, 63 and 91 days. Compressive strength and density tests have also been executed.FindingsThe superplasticizer admixture presented an optimal level of 0.35 per cent that significantly increased the electrical resistivity. The air AEs at the same dosage caused a considerable decrease in the electrical resistivity. The concrete with air AEs showed highest resistivity/MPa ratio.Research limitations/implicationsThe results should be carefully extrapolated for other materials and admixtures.Practical implicationsThe usage of chemicals admixture in concrete is extremely common nowadays. However, only a few authors have studied the impact of such materials on the concrete’s electrical resistivity. Since many other researchers have already correlated electrical resistivity with other concrete’s properties, such as strength, setting time and corrosion probability, it is important to better understand how superplasticizers and air-entraining agents, for instance, impact the resistivity.Originality/valueThe vast majority of studies only tested the resistivity of cement paste or mortar and usually for short period of time (up to 28 days), which seems not to be adequate since the cement reaction continues after that period. This paper fills this gap and studied the impact of admixture on concrete and for a period of 91 days.
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Tuskaeva, Zalina, i Soslan Karyaev. "Influence of various additives on properties of concrete". E3S Web of Conferences 164 (2020): 14007. http://dx.doi.org/10.1051/e3sconf/202016414007.
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A comparative analysis of concrete samples without chemical additives and three concrete samples with additives was carried out The first sample contains the liquid additive, the other two contain the powder additive. The article aims at finding out the effectiveness of additives influence on the physical and mechanical properties of concrete and the basis for the application areas of modified types of concrete. By means of laboratory tests, the physical and mechanical properties of concrete mixtures are determined. To determine the strength characteristics of concrete samples, the IM-1250M testing machine was used. The tests were carried out under the same temperature and humidity conditions. According to the results of the experiments, the samples with the multifunctional additive "D-5" showed the best characteristics of concrete, and the samples with the dolomite flour additive were the cheapest. As a result of the experimental analysis, the effects of three additives on the strength characteristics of concrete and water resistance were determined. Cemplast and D-5 additives are highly effective modifiers of concrete and mortar. They can increase the strength by 20-40% at the age of 28 days at dosages of 1.6-6% with a decrease in water-cement ratio and a decrease of cement amount by 20%. Additives highly increase the workability of the mixture, air entrainment and water resistance. While using the chemical additives an early set of the concrete design strength is observed for the construction time reducing in 7 days.
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Coutts, R. S. P. "Air-cured woodpulp, fibre/cement mortars". Composites 18, nr 4 (wrzesień 1987): 325–28. http://dx.doi.org/10.1016/0010-4361(87)90296-5.
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Dvorkin, Leonid, Patrycja Duży, Karolina Brudny, Marta Choińska i Kinga Korniejenko. "Adhesive Strength of Modified Cement–Ash Mortars". Energies 15, nr 12 (8.06.2022): 4229. http://dx.doi.org/10.3390/en15124229.
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The main aim of this article, carried out in relation to ash-cement mortars, is to determine the effect of complex additives of polyfunctional modifiers, including, in addition to superplasticizers, air-entraining and water-retaining additives, at different values of water–cement ratios. With the use of experimental–statistical models, the complex effect on the adhesive strength of cement–ash mortars of water–cement and ash–cement ratios, as well as complex additives of polyfunctional modifiers, including air-entraining and water-retaining additives, is considered. The extreme nature of the water–cement and ash–cement ratios on the adhesive strength of ash–cement mortars are established. Their optimal values are in the ranges of 0.7–0.75 and 0.35–0.4, respectively. The addition of a naphthalene-formaldehyde superplasticizer makes it possible to increase the adhesive strength of mortars by up to 40%. A positive effect is achieved along with the addition of a superplasticizer by introducing optimal amounts of air-entraining and water-retaining additives into the mortar mixtures. Quantitative parameters of mortar compositions that positively affect adhesive strength are established. The influence on the adhesive strength of the fly ash was also investigated, as well as on the binder–sand ratio. In addition, a positive effect on the adhesive strength of modified cement–ash mortars was experimentally shown by increasing the specific surface area of fly ash by regrinding it and increasing the cement–sand ratio.
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Nikoloutsopoulos, Nikolaos D., Sofia P. Nikolopoulou i Zacharias G. Pandermarakis. "Strength of Polypropylene Fiber Reinforced Cement Mortar Composites with Variable Water/Cement Ratio". Materials Science Forum 1042 (10.08.2021): 157–63. http://dx.doi.org/10.4028/www.scientific.net/msf.1042.157.
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For cement mortars the reinforcement techniques by randomly distributed short fibers, contribute highly to their micro-cracking stabilization and to improvement of their flexibility and tensile strength. Among the wide different types of short fiber reinforcement that have been used in the past for mortars, those made of steel, polymers and natural fibers dominate the area. It is a common sense that the reinforcement of mortars by polypropylene fibers (PP) is considered a very efficient method for reducing their curing shrinkage and enhanced toughness and strength of un-reinforced cemented material. In this study, PP fiber reinforced mortars were prepared with specific composition but with variable water to cement (W/C) ratio and appropriate superplasticizer amounts. For all mixtures their workability, air content and flexural and compressive strengths were measured. In conclusion it can be stated that even though W/C ratio of mortars is varied considerably, and also do their mechanical response, it is possible by appropriate mixture designing, for all studied compositions to produce suitable mortars that can be used successfully in a wide range of demands and applications, achieving high mortar strengths and ideal workability behavior.
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Marczewska, Julia. "Influence of the fly ash and the prior freezing and thawing on the sulphate resistance of cement mortars". MATEC Web of Conferences 174 (2018): 02004. http://dx.doi.org/10.1051/matecconf/201817402004.
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The use of fly ash for the production of cement is a typical example of the utilization of by-products (waste) from various fields of production in construction, a significant reduction of CO2 emissions and reduction of energy consumption. However, in order to be able to determine the suitability of this additive in construction, it is necessary to examine the durability of cement composites with fly ash in various, often complicated, destructive environments. There are known publications regarding the durability of concretes with fly ash in individual environments. However, in natural conditions, several destructive environments are common at the same time. The article presents an attempt to reproduce natural conditions. This paper presents the results of sulphate expansion tests of air-entrained (AE) and non-air-entrained (nAE) Portland and fly ash cement mortars subjected to prior freezing and thawing. Despite significant strains experienced during freeze-thaw cycles, unlike the non-air-entrained Portland cement mortars, the non-air-entrained mortars made of fly ash cement did not exhibit any significant expansion when exposed to Na2SO4. For 17 months no expansion was found in the air-entrained mortars made of either of the cement types when immersed in Na2SO4solution after freezethaw cycles. The results of the SEM and EDS analyses showed that gypsum and ettringite were the sulphate attack products in all the mortars. The highest amounts of ettringite were found in air voids.
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Knap, Monika, i Wojciech Piasta. "Effect of sulphate corrosion on the durability of air-entrained cement mortars". MATEC Web of Conferences 174 (2018): 02012. http://dx.doi.org/10.1051/matecconf/201817402012.
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Sulphate corrosion is a complex sequence of chemical and physical processes that, when the aqueous sulphate solutions are exposed for a sufficiently long time, irreversibly destroys the microstructure of cement paste. In order to determine the durability of Portland cement mortars, mortar resistance tests were carried out on a 5% solution of sodium sulphate by measuring linear deformations. The tests included 1 series of non air-entrained mortars and 3 series of air-entrained mortars with air content: 7%, 10% and 13%. The biggest deformations were observed for non air-entrained samples, the smallest for mortar with an air content of 13%. Compressive strength tests of mortars after 28 days and 80 weeks of residence in a solution of sodium sulphate were also carried out. For all mortars, the strength measured after 80 weeks immersion in Na2SO4 increased in relation to the strength after 28 days of maturation. Observations of the cement mortar microstructure using a scanning electron microscope (SEM-EDS) showed that ettringite was present in both the C-S-H structure and the air pores. By means of XRD analysis, the occurrence of crystalline materials was detected. Based on the research, it was found that air-entrained cement mortars showed greater durability in the context of sulphate corrosion.
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Maia Pederneiras, Cinthia, Rosário Veiga i Jorge de Brito. "Physical and Mechanical Performance of Coir Fiber-Reinforced Rendering Mortars". Materials 14, nr 4 (9.02.2021): 823. http://dx.doi.org/10.3390/ma14040823.
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Coir fiber is a by-product waste generated in large scale. Considering that most of these wastes do not have a proper disposal, several applications to coir fibers in engineering have been investigated in order to provide a suitable use, since coir fibers have interesting properties, namely high tensile strength, high elongation at break, low modulus of elasticity, and high abrasion resistance. Currently, coir fiber is widely used in concrete, roofing, boards and panels. Nonetheless, only a few studies are focused on the incorporation of coir fibers in rendering mortars. This work investigates the feasibility to incorporate coir fibers in rendering mortars with two different binders. A cement CEM II/B-L 32.5 N was used at 1:4 volumetric cement to aggregate ratio. Cement and air-lime CL80-S were used at a volumetric ratio of 1:1:6, with coir fibers were produced with 1.5 cm and 3.0 cm long fibers and added at 10% and 20% by total mortar volume. Physical and mechanical properties of the coir fiber-reinforced mortars were discussed. The addition of coir fibers reduced the workability of the mortars, requiring more water that affected the hardened properties of the mortars. The modulus of elasticity and the compressive strength of the mortars with coir fibers decreased with increase in fiber volume fraction and length. Coir fiber’s incorporation improved the flexural strength and the fracture toughness of the mortars. The results emphasize that the cement-air-lime based mortars presented a better post-peak behavior than that of the cementitious mortars. These results indicate that the use of coir fibers in rendering mortars presents a potential technical and sustainable feasibility for reinforcement of cement and cement-air-lime mortars.
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Kuziak, Justyna, Kamil Zalegowski, Wioletta Jackiewicz-Rek i Emilia Stanisławek. "Influence of the Type of Cement on the Action of the Admixture Containing Aluminum Powder". Materials 14, nr 11 (29.05.2021): 2927. http://dx.doi.org/10.3390/ma14112927.
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The study of the effect of cement type on the action of an admixture increasing the volume of concrete (containing aluminum powder), used in amounts of 0.5–1.5% of cement mass, was presented. The tests were carried out on cement mortars with Portland (CEM I) and ground granulated blast-furnace slag cement (CEM III). The following tests were carried out for the tested mortars: the air content in fresh mortars, compressive strength, flexural strength, increase in mortar volume, bulk density, pore structure evaluation (by the computer image analysis method) and changes in the concentration of OH− ions during the hydration of used cements. Differences in the action of the tested admixture depending on the cement used were found. To induce the expansion of CEM III mortars, a smaller amount of admixture is required than in the case of CEM I cement. Using the admixture in amounts above 1% of the cement mass causes cracks of mortars with CEM III cement due to slow hydrogen evolution, which occurs after mortar plasticity is lost. The use of an aluminum-containing admixture reduces the strength properties of the cement mortars, the effect being stronger in the case of CEM III cement. The influence of the sample molding time on the admixture action was also found.
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Janus, Magdalena, Szymon Mądraszewski, Kamila Zając, Ewelina Kusiak-Nejman, Antoni W. Morawski i Dietmar Stephan. "Photocatalytic Activity and Mechanical Properties of Cements Modified with TiO2/N". Materials 12, nr 22 (14.11.2019): 3756. http://dx.doi.org/10.3390/ma12223756.
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In this paper, studies of the mechanical properties and photocatalytic activity of new photoactive cement mortars are presented. The new building materials were obtained by the addition of 1, 3, and 5 wt % (based on the cement content) of nitrogen-modified titanium dioxide (TiO2/N) to the cement matrix. Photocatalytic active cement mortars were characterized by measuring the flexural and the compressive strength, the hydration heat, the zeta potential of the fresh state, and the initial and final setting time. Their photocatalytic activity was tested during NOx decomposition. The studies showed that TiO2/N gives the photoactivity of cement mortars during air purification with an additional positive effect on the mechanical properties of the hardened mortars. The addition of TiO2/N into the cement shortened the initial and final setting time, which was distinctly observed using 5 wt % of the photocatalyst in the cement matrix.
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Gołaszewska, Małgorzata, Jacek Gołaszewski, Jerzy Bochen i Grzegorz Cygan. "Comparative Study of Effects of Air-Entraining Plasticizing Admixture and Lime on Physical and Mechanical Properties of Masonry Mortars and Plasters". Materials 15, nr 7 (31.03.2022): 2583. http://dx.doi.org/10.3390/ma15072583.
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This article presents research on selected physical and mechanical properties of cement-based plasters and masonry mortars with consistency-improving additives, namely, traditional hydrated lime and a plasticizing and aerating mixture (APA), which, in practice, is often considered to be a lime substitute. Comparative analysis of the properties of mortars with alternative additives—lime or APA—was carried out, taking into consideration possible effects of cement, as two types of Portland cement were used for the research. For fresh mortar, mixture consistency, air content, resistance to segregation, and water retention were determined. Tests on hardened mortars included tests of porosity and impermeability, depth of penetration of water under pressure, drying shrinkage, as well as compressive and bending strength, modulus of elasticity, and adhesion of mortars to the base. In addition, research has shown that cement–lime mortars and cement mortars with APA admixture of similar consistency in the fresh state are characterized by significantly different properties. The results show, in most of the features analyzed, more favorable properties of mortars with the use of traditional lime. For shrinkage only, the use of admixture turned out to be more advantageous.
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Camarini, Gladis, Valdir Moraes Pereira, Pedro Murilo Gonçalves de Freitas i Regina Andrade Tirello. "Methods to Measure the Transfer Properties of Mortars". Applied Mechanics and Materials 148-149 (grudzień 2011): 184–87. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.184.
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The search for techniques and materials able to improve structure quality and durability has lead to research some methods that are able to measure the transfer properties of composites. Cement type has an important influence on mortar performance, and chemical and physical deteriorations modify microstructure, and thereby transfer properties. The aim of this work is to evaluate two methods which can measure the transfer properties of cement based materials: capillary absorption and air permeability tests in mortars produced with blastfurnace slag Portland cement. The relationship between these two methods was investigated. The mortars were submitted to steam curing (60 °C) and standard curing. Results show that steam curing improved initial compressive strength. At 28 days all mortars had the same performance. Water absorption coefficient and air permeability was higher for steam cured mortars. There was a significant correlation between both tests results.
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Jaworska-Wędzińska, Monika, i Iga Jasińska. "Durability of Mortars with Fly Ash Subject to Freezing and Thawing Cycles and Sulfate Attack". Materials 15, nr 1 (28.12.2021): 220. http://dx.doi.org/10.3390/ma15010220.
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Destruction of cement composites occurs due to the alternate or simultaneous effects of aggressive media, resulting in the destruction of concrete under the influence of chemical and physical factors. This article presents the results of changes in the measurement of linear strains of samples and changes in the microstructure of cement after 30 freezing and thawing cycles and immersed in 5% sodium sulfate solution. The compressive strengths ratios were carried out at the moment when the samples were moved to the sulfate solution after 30 cycles and at the end of the study when the samples showed visual signs of damage caused by the effect of 5% Na2SO4. The composition of the mixtures was selected based on the Gibbs triangle covering the area up to 40% replacement of Portland cement with low and high-calcium fly ashes or their mixture. Air-entrained and non-air entrained mortars were made of OPC, in which 20%, 26.6%, and 40% of Portland cement were replaced with low and/or high-calcium fly ash. Initial, freezing and thawing cycles accelerated the destruction of non- air-entrained cement mortars immersed in 5% sodium sulfate solution. The sulfate resistance, after the preceding frost damage, decreased along with the increase in the amount of replaced fly ash in the binder. Air-entrained mortars in which 20% of cement was replaced with high-calcium fly ash showed the best resistance to the action of sodium sulfate after 30 freezing and thawing cycles.
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Spychał, Edyta, i Anna Kotwa. "ASSESSMENT OF THE POSSIBILITY OF USING CHALCEDONITE POWDER AS A COMPONENT OF MORTARS". Structure and Environment 14, nr 4 (30.12.2022): 119–25. http://dx.doi.org/10.30540/sae-2022-014.
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The article presents the results of the assessment of the possibility of using chalcedonite powder as a partial replacement for cement in mortars. Portland cement CEM I 42.5 R was used as a binder, which was replaced in the amount of 5%, 20%, 35% and 50% with chalcedonite powder. The experimental tests concerned the determination of the technological and mechanical properties of mortars: consistency, air content, compressive and bending strength, supplemented by X-ray diffraction analysis and calorimetric measurements of the pastes. The research results indicate that chalcedonite powder can be used in the production of mortars. The best mechanical properties of tested mortars were obtained in the case of replacing cement with the addition of powder in the amount of 5% and 20%.
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Chajec, Adrian. "Granite Powder vs. Fly Ash for the Sustainable Production of Air-Cured Cementitious Mortars". Materials 14, nr 5 (4.03.2021): 1208. http://dx.doi.org/10.3390/ma14051208.
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The partial replacement of cement in concrete with the addition of granite powder and fly ash can help to reduce the carbon dioxide (CO2) emissions into the atmosphere associated with cement production. The aim of the article is to compare the performance of granite powder and fly ash for the sustainable production of air-cured cementitious mortars. The morphological, chemical, and granulometric properties of these additives were first compared with the properties of cement. Afterward, a series of mortars modified with the addition of granite powder and fly ash was made. The properties of the fresh mixes and the mechanical properties of the hardened composites were then tested. Finally, based on the obtained results, a cost analysis of the profitability of modifying cementitious composites with granite powder or fly ash was investigated. The obtained results allow similarities and differences between granite powder and fly ash in relation to cement to be shown. To conclude, it should be stated that both of these materials can successfully be used for the sustainable production of air-cured cementitious composites. This conclusion has a significant impact on the possibility of improving the natural environment by reducing the amount of cement production. More sustainable production of cement-based materials could enable CO2 emissions to be decreased. The use of granite powder for the production of cementitious mortars can significantly reduce the amount of this material deposited in landfills.
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Spychał, Edyta, i Piotr Stępień. "Effect of Cellulose Ether and Starch Ether on Hydration of Cement Processes and Fresh-State Properties of Cement Mortars". Materials 15, nr 24 (8.12.2022): 8764. http://dx.doi.org/10.3390/ma15248764.
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The production of factory-made mortars is a multicomponent system. Viscosity-modifying admixtures (VMAs) are an inherent ingredient of these materials. The correct choice of the amount and type of these admixtures is important from the practical and scientific points of view. In this article, the use of cellulose ether (CE) and starch ether (SE) in cement pastes and mortars is studied. This research focuses on the hydration process and fresh-state properties of mortars because this subject determines the correct choice of the amount and type of admixture used, and the results determine the application and properties of hardened mortars. Polymers were added in the range from 0.056% to 0.22% in relation to the dry ingredients of the mortar. The research showed that cellulose ether had the greatest impact on the consistency, air content, bulk density, and water retention of ordinary dry-mix mortars. On the other hand, starch ether affected the hydration process, delaying the setting and hardening processes much more than cellulose ether. The action of these admixtures rose with the increase in the amount of polymer used in different ways (depending on the type of ether).
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Liu, Si Feng, i Pei Ming Wang. "Early-Age Free Shrinkage of Mortars with Different Dosages of EVA Redispersible Powder". Key Engineering Materials 539 (styczeń 2013): 49–54. http://dx.doi.org/10.4028/www.scientific.net/kem.539.49.
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The plastic free shrinkage evolutions of mortars in the presence of different dosages of redispersible Ethylene-vinyl acetate (EVA) copolymer powder were measured using the laser sensor at acceleration dry for 6 hours. The effects of temperature, relative humidity, air contents and water evaporation of mortars on the plastic free shrinkage were observed. The plastic free shrinkage of mortars declines firstly and then rise under the increasing dosage of EVA powder in range of 1%~10% mass of cement in mortars, the plastic free shrinkage of mortars with 10% EVA powder was almost closed to that of plain cement mortars. The EVA powder facilitates a decrease in plastic free shrinkage of mortars. The linear regression equation between the plastic free shrinkage and its effect factors was set up, and analysis of variance was used to analyze the significant of air content and water evaporation.
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Dinler, Ebru. "An evaluation of cooling Portland cement mortars exposed to high temperature, by using firefighting foam". Cement Wapno Beton 27, nr 6 (19.04.2023): 425–35. http://dx.doi.org/10.32047/cwb.2022.27.6.5.
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The purpose of this study was to investigate the effects of cooling Portland cement mortars exposed to high temperature, with synthetic high-expansion firefighting foam. In this experimental study, mortar samples produced with Portland cement CEM I 42,5R, Rilem-Cembureau sand and tap water were first subjected to water curing for 28, 90 and 180 days and then exposed to 20°C, 150°C, 300°C, 500°C and 700°C for 3 hours, respectively. Cement mortars exposed to high temperatures were cooled with high expansion firefighting foam and the resulting flexural strength and compressive strengths were evaluated according to hydration period and temperature parameters. Subsequently, 180-day cement mortar samples exposed to high temperature were cooled using air, water, and foam cooling methods. It was determined that the air cooling method resulted in a higher compressive strength than water or foam cooling. The flexural strength, compressive strength, ultrasonic pulse velocity, and mass loss percentage values, obtained by the different cooling methods and exposure temperatures employed, were then analysed. It was determined that samples exposed to 500°C, cooling with firefighting foam, yielded a compressive strength of 9% higher, compared to water cooling. SEM images of 180-day Portland cement mortars exposed to 20°C, 300°C and 700°C and subsequently air, water and foam cooled, respectively, were obtained and analysed.
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Łaźniewska-Piekarczyk, Beata. "The Influence of W/C Ratio and Superplasticizer Type on Porosity of Concrete with Air-Entraining Cement with Fly Ash". Solid State Phenomena 279 (sierpień 2018): 266–70. http://dx.doi.org/10.4028/www.scientific.net/ssp.279.266.
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The research results of stability of air-entrainment of concrete acc. PN-EN 480-1 in case of innovate air-entraining multi-component cement CEM II/B-V is presented in the paper. The influence of PCE, naphthalene and phosphonamidite based superplasticizers and w/c ratio: 0.45, 0.50 and 0.55 on air-entrainment and consistency of fresh concrete mix was investigated. The research results indicated that with increasing w/c ratio the air-entrainment of concrete increases. Moreover, in case of an increase in the degree of liquidity of the air-entrained concrete made of participation of the innovative, air-entraining multi-component cement CEM II/B-V, first and new generation superplasticizers based on modified naphthalene, and then modified phosphonamidite should be used. PCE based superplasticizer cause the too high air-entrainment of concrete. The research results proved, that the porosity of hardened concrete meets the European standards for frost-resistant concrete.
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Kravchenko, Igor, Mihail Erofeev, Aleksandr Fedorov, Valeriy Kondrashchenko, Diana Abdumuminova, Shukurilo Yuldashev, Jaloliddin Matyokubov i Kudrat Bobomurodov. "Research of Mechanochemical Processes of Activation of Building Materials by Air-Impact Method". E3S Web of Conferences 304 (2021): 02009. http://dx.doi.org/10.1051/e3sconf/202130402009.
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To increase the specific surface area of the binder and accelerate the strength gain of fast-hardening concrete mixtures, a model has been created for calculating aeroactivators as part of mobile complexes based on new equipment for cement activation, sand enrichment, local materials, and production waste. The proposed model establishes the dependence of the rate of destruction of the dusty shell of particles on the mechanical impact of the beaters and materials` physical and mechanical characteristics. To improve the operational characteristics of the cement aeroactivator, experimental studies were carried out, the results of which made it possible to determine the rational parameters of the developed installation. Based on the test results, it was found that the use of the cement activation process with additives accelerates the hardening process of concrete and mortar mixtures in the initial period, increases the design strength of concretes and mortars by 20–40% in comparison with the strength of the control composition at the same cement consumption, and also reduces the consumption cement up to 17% to obtain concretes and mortars equal to the control composition at the design age.
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Baran, Edyta, Mariusz Hynowski, Łukasz Kotwica i Jacek Rogowski. "Effect of Portland Cement on the Selected Properties of Flue Gas Desulfurization Gypsum-Based Plasters". Materials 16, nr 14 (18.07.2023): 5058. http://dx.doi.org/10.3390/ma16145058.
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The introduction of the European Union’s climate change legislation and the intended use of renewable energy sources instead of fossil fuels will significantly reduce the production of flue gas desulfurization (FGD) gypsum used as the raw material for gypsum mortar plasters’ production. This has forced mortar producers to look for alternative materials, including gypsum–cement composites. This work investigated the mechanical strength and linear extension of four gypsum–cement mortars with the gypsum content reduced to 30%. The authors showed that the cement admixture of 6 to 12% introduced into the prepared mortars resulted in the formation of gypsum–cement mortars, which fulfill the requirements of the EN 13279-1:2008 standard concerning mechanical strength. This publication took into account the use of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffractometry to characterize the chemical and phase composition of the mortars up to 180 days of dry air curing and increased relative humidity (RH) conditions. The formation of thaumasite, ettringite, and mixed ettringite–thaumasite phases was interesting because of their deleterious effect on the durability of plaster mortars.
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Sanytsky, Myroslav, Tetiana Kropyvnytska, Roman Kotiv, Mykola Bevz i Stanislav Fic. "Suitability of modified low carbon Roman cements for architectural restoration". E3S Web of Conferences 280 (2021): 07002. http://dx.doi.org/10.1051/e3sconf/202128007002.
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Article is devoted to the investigation of suitability of low carbon Roman cement for restoration and finishing works. The history of the development of Roman cement as a natural hydraulic binder, which was commonly used to decorate building facades in the 19th and early 20th centuries, is presented. The properties of mortars based on Roman cement make it an excellent product for architectural restoration and conservation, as they are characterized by fast setting, high porosity typical for lime mortars, high resistance to weather conditions, high initial strength. At the same time, due to the high surface activity and increased water demand for cement, with the age of hardening, shrinkage deformations can develop, which leads to the formation of main cracks on the surface of the products. It is shown that the addition of gypsum is an effective regulator of the setting time of Roman cement and contributes to an increase in the strength of the cement paste. Analogs of Roman cement based on multicomponent cement binders modified with plasticizing and air-entraining additives are presented.
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Polverino, Salvatore, Antonio Esau Del Rio Castillo, Antonio Brencich, Luigi Marasco, Francesco Bonaccorso i Renata Morbiducci. "Few-Layers Graphene-Based Cement Mortars: Production Process and Mechanical Properties". Sustainability 14, nr 2 (11.01.2022): 784. http://dx.doi.org/10.3390/su14020784.
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Cement is the most-used construction material worldwide. Research for sustainable cement production has focused on including nanomaterials as additives to enhance cement performance (strength and durability) in recent decades. In this concern, graphene is considered one of the most promising additives for cement composites. Here, we propose a novel technique for producing few-layer graphene (FLG) that can fulfil the material demand for the construction industry. We produced specimens with different FLG loadings (from 0.05% to 1% by weight of cement) and curing processes (water and saturated air). The addition of FLG at 0.10% by weight of cement improved the flexural strength by 24% compared to the reference (bare) sample. Similarly, a 0.15% FLG loading by weight of cement led to an improvement in compressive strength of 29% compared to the reference specimen. The FLG flakes produced by our proposed methodology can open the door to their full exploitation in several cement mortar applications, such as cementitious composites with high durability, mechanical performance and high electrical conductivity for electrothermal applications.
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Azevedo, Afonso, Thuany Lima, Noan Simonassi, Matheus Pereira Ribeiro, Fabio Garcia Filho i Sergio Monteiro. "Piassava Fiber: A Novel Reinforcement for Cement-Based Matrix Composites". Concilium 22, nr 1 (15.02.2022): 379–90. http://dx.doi.org/10.53660/clm-150-166.
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The addition of 2 and 5 wt% of piassava fiber, a natural lignocellulosic fiber extracted from a Brazilian palm tree botanically named Attallea funifera, into cement-based matrix composites was investigated. Both alkali-treated piassava fibers by NaOH and non-treated fibers were embedded in Portland cement, lime, and sand to fabricate mortars intended for civil construction. The non-aged fresh mortars were tested for paste consistency, water retention, and relative volume of incorporated air. Preliminary results showed that the addition of NaOH-treated piassava slightly increased the water retention while decreasing the incorporated air content. Together with these preliminary results, the comparatively low density of the piassava fiber allows the fabrication of novel cement-based composite with the potential to be used as mortar in building construction.
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Vyšvařil, Martin, Libor Topolář i Richard Dvořák. "Acoustic insulation properties of lime mortars with natural lightweight aggregate". MATEC Web of Conferences 282 (2019): 02075. http://dx.doi.org/10.1051/matecconf/201928202075.
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Porous pozzolan-active aggregate can be used to prepare lightweight lime mortars with high ability to salt accumulation from masonry, enhanced strengths and improved their acoustic and thermal insulation properties, or fire resistance. In this study, the effect of 3 types of natural lightweight aggregate on acoustic insulation properties of air lime mortars, NHL mortars, and cement-lime mortars has been investigated. Measurements of the signal attenuation in the frequency range of 16 Hz to 16 kHz showed the appreciable effect of binder and aggregate used in the mortars. Pumiceous aggregate caused the highest attenuation of the acoustic signal. The natural zeolite seems to be suitable aggregate to NHL and blended lime-cement plasters because it lightens the mortar and positively affects the acoustic attenuation.
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Sequeira, Lucas, Blas Cantero, Miguel Bravo, Jorge de Brito i César Medina. "The Influence of Recycled Cement, Fly Ash, and Magnesium Oxide on the Mechanical Performance of Sustainable Cementitious Materials". Materials 16, nr 7 (30.03.2023): 2760. http://dx.doi.org/10.3390/ma16072760.
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In the construction industry, cement is the most widely used material. So, to achieve greater sustainability in this industry, it is imperative to improve the sustainability of this material. One way to reduce the ecological footprint of cement is to replace it, even if partially, with other more sustainable materials that can act as binders. This paper analyses the mechanical properties of more sustainable mortars containing recycled cement (RC), fly ash (FA), and magnesium oxide (MgO). Different types of binary, ternary, and quaternary mortars were used: containing recycled cement (5% and 10%), fly ash (10% and 20%), and MgO (7.5% and 15%). An experimental campaign was carried out analysing air content, density, compressive and flexural strengths, modulus of elasticity, and ultrasonic pulse velocity. The ternary mortars showed decreases between 0.4% (M-5RC10FA) and 35.3% (M-10RC15Mg) in terms of compressive strength at 365 days (compared to RM), when the theoretically expected decrease (the sum of the decreases obtained with the individual incorporation of these materials) would be between 16.6% and 41.5%, respectively. The results obtained allow for concluding that the joint use of these materials in ternary mortars improves the mechanical capacity, relative to the individual incorporation of each material in binary mortars.
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Tarhan, Yeşim, i Remzi Şahin. "Fresh and Rheological Performances of Air-Entrained 3D Printable Mortars". Materials 14, nr 9 (5.05.2021): 2409. http://dx.doi.org/10.3390/ma14092409.
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The effect of air-entraining admixture (AEA) on the fresh and rheological behavior of mortars designed to be used in 3D printers was investigated. Blast furnace slag, calcined kaolin clay, polypropylene fiber, and various chemical additives were used in the mortar mixtures produced with Super White Cement (CEM I 52.5 R) and quartz sand. In addition to unit weight, air content, and compressive strength tests, in order to determine the stability of 3D printable mortar elements created by extruding layer by layer without any deformation, extrudability, buildability, and open time tests were applied. Fresh and rheological properties of 3D printable mortars were also determined. It was concluded that the addition of AEA to the mortars decreased the unit weight, viscosity, yield, and compressive strength, but increased the air content, spread diameter, initial setting time, and thixotropy of 3D printable mortar. It is recommended to develop a unique chemical admixture for 3D printable mortars, considering the active ingredients of the chemical additives that affect fresh and rheological performance of mortar such as superplasticizer, viscosity modifying, and cement hydration control.
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Rattanaveeranon, Santi, Sarote Dumrongsil i Knavoot Jiamwattanapong. "Effect of Latex Rubber and Rubber Powder as an Admixture on Bending Strength of Cement Mortars". Applied Mechanics and Materials 891 (maj 2019): 180–86. http://dx.doi.org/10.4028/www.scientific.net/amm.891.180.
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This paper reported the effect of latex rubber (LR) and rubber powder (RP) on the bending strength of cement mortars containing fly ash silica (FAS) prepared from sugarcane bagasse. The bending strengths of the cement mortars with the addition of LR and RP were compared. The study was conducted by adding 5-10 wt% of each admixture into cement mortar specimens and left in air atmosphere for 28 days before measuring their bending strength. At 5 wt.%, both LR or RP could significantly reinforce the bending strength of the mortar. The bending strength of cement mortars decreased when the proportion of the LR and RP were higher than 5 wt%. In addition, at 10 wt%, LR provided better bending strength than that of RP, i.e. the bending strength of mortar contained LR was 550 ksc, whereas that contained RP was 85 ksc. The bending strength of mortar with LP was much higher than that of the pure cement mortar (20 wt% FAS : 80 wt% cement) which was about 62 ksc. The low bending strength of the mortar with 10 wt% RP may be due to the decrease of Si-O-Si hybrid compounds which was inhibited by the hydroxyl group during the hydrolyzation process.
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Tassos, Christos, Kosmas Sideris, Alexandros Chatzopoulos, Nikolaos Pistofidis i Emmanouil Chaniotakis. "Influence of cement type on carbonation of concrete mixtures". MATEC Web of Conferences 163 (2018): 05005. http://dx.doi.org/10.1051/matecconf/201816305005.
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This research aims to investigate the influence of cement type to carbonation. For this purpose mixtures of four different cement mortars and eight different concretes that have been prepared with four different cements were left exposed for one year in open air in northern Greece. Results indicate that the type of cement influences the carbonation rate. Concrete mixtures produced according to the definitions of EN 206 standard perform lower service life against carbonation induced corrosion if the choice of the cement type is not carefully examined.
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Kim, Hayeon, i H. M. Son. "Effects of Air Entrainment on Bacterial Viability in Cement Paste". Materials 15, nr 6 (15.03.2022): 2163. http://dx.doi.org/10.3390/ma15062163.
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This study investigated the effect of air entrainment (AE) on bacterial viability in cementitious materials. Specimens were fabricated with Portland cement, urea, calcium lactate, and ureolytic bacteria, and with varying amounts of an AE agent. Specimens with different amounts of the AE agent were fabricated, and then a compressive strength test, quantitative polymerase chain reaction, X-ray diffraction, and thermogravimetry were used to investigate the mechanical properties, viability of bacteria, and hydrates of the specimens. The highest compressive strength was achieved by the specimen with 0.3% AE agent, while the compressive strength of the specimens decreased considerably when the incorporated AE agent was over 0.6%, due to increased porosity. The quantitative polymerase chain reaction result showed that the cell number of the viable bacteria was increased by incorporation of the AE agent, which also corresponded with an increase in CaCO3 due to microbial mineral formation. The obtained result confirmed the positive effect of AE agent incorporation in cementitious materials containing bacterial admixtures, as the viability of bacteria, which play a vital role in self-healing efficiency of concrete, was increased by the space provided by the AE agent in the cement matrix. In addition, the quantity of CaCO3 and the compressive strength were highest when 0.3% AE agent was incorporated.
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Sypek, Maciej, Rafał Latawiec, Beata Łaźniewska-Piekarczyk i Waldemar Pichór. "Impact of Surfactant and Calcium Sulfate Type on Air-Entraining Effectiveness in Concrete". Materials 15, nr 3 (27.01.2022): 985. http://dx.doi.org/10.3390/ma15030985.
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The paper presents the evaluation of the influence of calcium sulfate on the air void microstructure in concrete and its action mechanism depending on the character of the air-entraining agent. Gypsum dehydration has been previously proven to negatively influence the air void structure of air-entrained concrete. Ettringite, nucleating from tricalcium aluminate and calcium sulfate, influences the adsorption and mode of action of anionic-based polycarboxylate ether admixtures. The authors suspected the admixture’s air-entraining mechanism was also affected by these characteristics. Gypsum dehydration was confirmed to influence the air void structure. In the case of the anionic surfactant, the content of air bubbles smaller than 300 µm was lower compared to cement with gypsum and hemihydrate. On the other hand, the content of air voids with a diameter up to 60 µm, which are the most favorable, was higher. The results obtained led to the conclusion that the mechanism of air entrainment was twofold, and in most cases occurred through the lowering of surface tension and/or through the adsorption of surfactant on cement grains. The adsorptive mechanism was proved to be more effective in terms of the total air content and the structure of the air void system. The results and conclusions of the study provide guidelines to determine the proper surfactant type to reduce the risk of improper air entrainment of concrete, and emphasize the importance of gypsum dehydration of cement in the process of air entrainment.
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Berkak, Hichem, Zoubir Makhloufi, Madani Bederina, Abdellah Demdoum i Yacine Hadj Aissa. "Physico-mechanical characterization of composite cementitious mortars modified by resin containing antifoam". MATEC Web of Conferences 149 (2018): 01067. http://dx.doi.org/10.1051/matecconf/201814901067.
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Nowadays, polymer-modified mortars (PMM) are generally used in the field of building as finishing materials. In general, The properties of the fresh and hardened PMC are affected by several factors that tend to interact each other: the nature of materials used as latex, cement and aggregates; the mix proportions (W/C, polymer/cement ratio, etc.); air content; type and amount of surfactants and anti-foaming; and curing methods. This present experimental work aims to study the influence of the rate of partial substitution of cement by resin containing anti-foaming on the properties of composite mortars in the fresh and hardened state particularly workability, tensile and compressive strengths at different times (3, 7 and 28 days) and module of static elasticity at 28 days. For that purpose, seven mortar combinations were developed from the various substitution percentages (0 to 15% by step of 2.5%). The treatment of the obtained results reveals that this partial replacement of the cement by resin improves, clearly, the workability of mortars and decreases the report W/C at the same time. Besides, the incorporation of resin affects significantly the mechanical strengths, and consequently, the addition by substitution of the polymer-latex improves, slightly, the mechanical behavior in tensile where the rates of increase range from 2.20% to 8.54% for replacement percentages of 2.5% and 15%, respectively. Furthermore, the compressive strengths of cement - resin composite mortars are lower compared to the reference mortar made with the cement Portland (CEM I). The notable decrease in compressive strength of polymer–modified mortars can be justified by the reduction of cementitious part, in hybrid materials, which is an indispensable and responsible part of improving compressive strength.
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Casali, Juliana Machado, Fernanda Domigues Melo, Vitoria Carminatti Serpa, Alexandre Lima de Oliveira, Andrea Murillo Betioli i Luciana Maltez Lengler Calçada. "Influence of cement type and water content on the fresh state properties of ready mix mortar". Ambiente Construído 18, nr 2 (kwiecień 2018): 33–52. http://dx.doi.org/10.1590/s1678-86212018000200241.
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Abstract The main characteristic of ready mix mortar is to remain workable for up to 72hours after mixing. This greater duration of workability is obtained by use of hydration stabilizing admixtures and air-entrained admixtures. Thus, the behavior of this mortar depends on the compatibility between Portland cement and these two admixtures. Within this context, the objective of this article is to evaluate the influence of Portland cement type and water content on the properties of ready mix mortars in fresh state. Three types of Portland cement and four water/dry material ratios were evaluated. The produced mortars were analyzed with respect to their properties in fresh state: consistency index, specific gravity, air entrained content and rheological behavior by squeeze-flow. The properties were determined for three storage durations (0, 24 and 48 hours). The results show that both types of cement (mainly, the rheological behavior) and water content (mainly, the air entrained content, consistency and rheological behavior) influenced the ready mix mortar properties. Therefore, these two parameters must be evaluated for mortar dosages in order to obtain the required properties in fresh state.
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Cantero, Blas, Miguel Bravo, Jorge de Brito, Isabel Fuencisla Sáez del Bosque i César Medina. "The Influence of Fly Ash on the Mechanical Performance of Cementitious Materials Produced with Recycled Cement". Applied Sciences 12, nr 4 (21.02.2022): 2257. http://dx.doi.org/10.3390/app12042257.
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Concrete is the most widely used construction material in the world; as such, the best way to promote a more sustainable construction industry is to improve the environmental performance of this material. Since cement production is the main source of the high environmental impact of concrete, due to the high calcination temperature that clinker requires, replacing this binder with recycled cement would allow for the establishment of a new concrete design with a much lower ecological footprint. This research intends to analyse the mechanical performance of mortars with recycled cement and fly ash. Mixes with two replacement ratios of recycled cement (5% and 10%) were studied separately or in combination with fly ash (10% and 20%). An exhaustive experimental programme was designed to assess the variation in air content, density, compressive and flexural strengths, modulus of elasticity, and ultrasonic pulse velocity. The results suggest that the simultaneous use of recycled cement and fly ash improves the mechanical performance of mortars relative to those with recycled cement only or fly ash only.
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Vyšvařil, Martin, Michaela Hegrová i Tomáš Žižlavský. "Influence of Cellulose Ethers on Fresh State Properties of Lime Mortars". Solid State Phenomena 276 (czerwiec 2018): 69–74. http://dx.doi.org/10.4028/www.scientific.net/ssp.276.69.
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Cellulose ethers (CEs) are widely used as viscosity enhancing, water retaining additives in cement based mortars. Nevertheless, studies about the effect of cellulose ethers on the properties of aerial lime-based mortars are very lack. The use of water retaining additives in lime mortars can influence not only their fresh state properties but also the pore structure and strength of hardened mortars. In this work, four different commercial cellulose ethers were added to lime mortars in order to test their influence on properties of mortars in the fresh state. Mortar rheological parameters (relative yield stress, consistency coefficient and fluidity index) were correlated with flow table tests, relative density measurements, water retention and air content in the mortars. It was found that CEs reduce the spread of lime mortars and increase air content in the mortars. The CEs are not so effective in water retention compared with other types of water retention agents. Most dosages of CEs change the behaviour of mortars from pseudoplastic to dilatant. In contrast to the effect of CEs in cement-based materials, their viscosity enhancing behavior in lime mortars is denied, due to the presence of large amounts of calcium hydroxide. From this point of view, the CEs are not so suitable to use as viscosity enhancing admixtures in lime mortars like derivatives of chitosan or guar gum.