Showing papers on "Mortar published in 2007"
TL;DR: In this paper, the properties of cement mortars with nano-SiO 2 were experimentally studied, and the results showed that the compressive strength of mortars containing nano SiO 2 particles was significantly higher than those of those containing silica fume at 7 and 28 days.
867 citations
TL;DR: The uniaxial monotonic compressive stress-strain behavior and other characteristics of unreinforced masonry and its constituents, i.e., solid clay bricks and mortar, have been studied by several laboratory tests.
Abstract: The uniaxial monotonic compressive stress-strain behavior and other characteristics of unreinforced masonry and its constituents, i.e., solid clay bricks and mortar, have been studied by several laboratory tests. Based on the results and observations of the comprehensive experimental study, nonlinear stress-strain curves have been obtained for bricks, mortar, and masonry and six “control points” have been identified on the stress-strain curves of masonry, which can also be used to define the performance limit states of the masonry material or member. Using linear regression analysis, a simple analytical model has been proposed for obtaining the stress-strain curves for masonry that can be used in the analysis and design procedures. The model requires only the compressive strengths of bricks and mortar as input data, which can be easily obtained experimentally and also are generally available in codes. Simple relationships have been identified for obtaining the modulus of elasticity of bricks, mortar, and ...
550 citations
TL;DR: In this article, three pre-soaking treatment approaches, namely, ReMortarHCl, Re MortarH2SO4, and ReMORTARH3PO4, were used to reduce the mortar attached to the aggregate.
Abstract: With a rising tide of adoption of recycled aggregate (RA) for construction, investigation on ways to improve the quality of RA has been overwhelming. The adoption of RA brings benefits including savings in the limited landfill spaces and the use of natural resources. However, the poorer quality of RA often limits its utilization to low grade applications such as sub-grade activities, filling materials and low grade concrete. The major reason that affects the quality of RA is the large amount of cement mortar remains on the surface of the aggregate, resulting in higher porosity, water absorption rates and thus a weaker interfacial zone between new cement mortar and aggregates, which weakens the strength and mechanical performance of concrete made from RA. This paper attempts to study three pre-soaking treatment approaches; namely ReMortarHCl, ReMortarH2SO4 and ReMortarH3PO4 in reducing the mortar attached to RA. The results show that the behaviour of RA has improved with reduction in water absorption, without simultaneous exceeding the limits of chloride and sulphate compositions after the treatment. This work has also compared the compressive strength, flexural strength and modulus of elasticity of concrete made from the approaches, which shows marked improvements in quality when compared with those using traditional approaches.
458 citations
TL;DR: In this article, the application of textile-reinforced mortar (TRM) as a means of increasing the load carrying capacity and deformability of unreinforced masonry walls subjected to cyclic in-plane loading is experimentally investigated.
Abstract: In this study the application of a new structural material, namely textile-reinforced mortar (TRM), as a means of increasing the load carrying capacity and deformability of unreinforced masonry walls subjected to cyclic in-plane loading is experimentally investigated. The application of externally bonded TRM is considered in this work as an alternative method to the application of fiber-reinforced polymers (FRP). Hence, the effectiveness of TRM overlays is evaluated in comparison to the one provided by FRPs. Medium-scale tests were carried out on 22 masonry walls subjected to in-plane cyclic loading. Three types of specimens were used: (a) shear walls; (b) beam-columns; and (c) beams. The parameters under investigation included the matrix material (mortar versus resin), the number of textile layers and the compressive stress level applied to shear walls and beam-columns. Compared with their resin-impregnated counterparts, mortar-impregnated textiles may result in generally lower effectiveness in terms of strength, but in much higher in terms of deformability. From the results obtained in this study it is believed that TRMs hold strong promise as a solution for the structural upgrading of masonry structures under in-plane loading.
450 citations
TL;DR: In this paper, the authors link the molecular structure of polycarboxylate-ether-type superplasticizers with the performance of cementitious systems in order to develop new products with enhanced properties, e.g. improved water reduction with a wide range of cements or reduced retardation of cement hydration.
Abstract: The objective of this study is to link the molecular structure of polycarboxylate-ether-type superplasticizers with the performance of cementitious systems in order to develop new products with enhanced properties, e.g. improved water reduction with a wide range of cements or a reduced retardation of cement hydration. Different experimental superplasticizers have been synthesized varying length and density of the polyether chains as well as the molecular weight of the polymer. The influence of these polymers on the properties of cement pastes and mortars was determined using various characterization methods like mortar flow, rheological and calorimetric measurements, adsorption measurements and mortar compressive strength. Characteristic connections between molecular structure of the polycarboxylate-type water reducers, adsorption behaviour, workability and retarding effect have been determined allowing the synthesis of new superplasticizers with improved performance.
416 citations
TL;DR: In this article, the use of ternary blended cement improves the early age and the long-term compressive and flexural strengths of mortar prisms in which Portland cement was replaced by up to 20%LF and 30%NP at 2, 7, 28 and 90 days.
Abstract: The benefits of limestone filler (LF) and natural pozzolana (NP) as partial replacement of Portland cement are well established. Economic and environmental advantages by reducing CO2 emission are well known. However, both supplementary materials have certain shortfalls. LF addition to Portland cement causes an increase of hydration at early ages inducing a high early strength, but it can reduce the later strength due to the dilution effect. On the other hand, NP contributes to hydration after 28 days improving the strength at medium and later ages. Hence, ternary blended cement (OPC–LF–NP) with better performance could be produced. In this paper, mortar prisms in which Portland cement was replaced by up to 20%LF and 30%NP were tested in flexure and compressive strength at 2, 7, 28 and 90 days. Some samples were tested under sulfate and acid solutions and for chloride ions permeability. Results show that the use of ternary blended cement improves the early age and the long-term compressive and flexural strengths. Durability was also enhanced as better sulfate, acid and chloride ions penetration resistances were proved. (A) “Reprinted with permission from Elsevier”.
373 citations
TL;DR: A priori error estimates are derived and show, with appropriate choice of the mortar space, optimal order convergence and some superconvergence on the fine scale for both the solution and its flux.
Abstract: We develop multiscale mortar mixed finite element discretizations for second order elliptic equations. The continuity of flux is imposed via a mortar finite element space on a coarse grid scale, while the equations in the coarse elements (or subdomains) are discretized on a fine grid scale. The polynomial degree of the mortar and subdomain approximation spaces may differ; in fact, the mortar space achieves approximation comparable to the fine scale on its coarse grid by using higher order polynomials. Our formulation is related to, but more flexible than, existing multiscale finite element and variational multiscale methods. We derive a priori error estimates and show, with appropriate choice of the mortar space, optimal order convergence and some superconvergence on the fine scale for both the solution and its flux. We also derive efficient and reliable a posteriori error estimators, which are used in an adaptive mesh refinement algorithm to obtain appropriate subdomain and mortar grids. Numerical experi...
320 citations
TL;DR: In this paper, the results of an experimental investigation on the chloride transport properties of engineered cementitious composites (ECC) under combined mechanical and environmental loads were presented, and the results showed that ECC is a newly developed, high-performance, fiber-reinforced cementitious composite with substantial benefit in both high ductility and improved durability due to tight crack width.
Abstract: This paper presents the results of an experimental investigation on the chloride transport properties of engineered cementitious composites (ECC) under combined mechanical and environmental loads. ECC is a newly developed, high-performance, fiber-reinforced cementitious composite with substantial benefit in both high ductility and improved durability due to tight crack width. By employing micromechanics-based material design, maximum ductility in excess of 3% under uniaxial tensile loading can be attained with only 2% fiber content by volume, and the typical single crack fracture behavior commonly observed in normal concrete or mortar is converted to multiple microcracking in ECC. In this study, immersion and salt ponding tests were conducted to determine chloride ion transport properties. Under high imposed bending deformation, the preloaded ECC beam specimens reveal microcracks less than 50 μm and an effective diffusion coefficient significantly lower than that of the similarly preloaded reinforced mortar beam because of the tight crack width control in ECC. In contrast, cracks larger than 150 μm are easily produced under the same imposed deformation and have significant effects on effective diffusion coefficient of reinforced mortar. Moreover, through the formation of microcracks, a significant amount of self-healing was observed within the ECC cracks subjected to NaCl solution exposure.
276 citations
TL;DR: In this article, the sulfate resistance of blended Portland cement with fly ash and ground rice husk ash (RHA) was studied, and it was shown that RHA was more effective than fly ash in reducing the expansion of the mortar bars and the pH values.
232 citations
TL;DR: In this paper, an epoxy emulsion based polymer system has been developed for improving the properties of plain cement mortar or concrete, which has superior strength properties and better resistance to the penetration of chloride ions and carbon dioxide.
225 citations
TL;DR: In this article, the compressive strengths of concrete bricks with nano-SiO 2 particles (NS) were evaluated at various water-cementitious material ratios (w/cm).
Abstract: The amorphous or glassy silica, which is the major component of a pozzolan, reacts with calcium hydroxide formed from calcium silicate hydration. The rate of the pozzolanic reaction is proportional to the amount of surface area available for reaction. Therefore, it is plausible to add nano-SiO 2 particles (NS) to make high-performance concrete. The compressive strengths of cement mortar were evaluated at various water-cementitious material ratios (w/cm). Five different w/cm were used, including 0.23, 0.25, 0.32, 0.35, and 0.48 and four contents of NS, 3, 6, 9, and 12% by weight of cement. The compressive strengths of cement mortar with the addition of silica fume were also evaluated at a w/cm of 0.35 to compare with mortar containing nano-SiO 2 particles and three contents of silica fume were: 5, 10, and 15% by weight of cement. The experimental results show that the compressive strengths of mortars with NS were all higher than those of mortars containing silica fume at 7 and 28 days. It was demonstrated that the nano-particles were more valuable in enhancing strength than silica fume. This paper also analyzes some available examinations to monitor the hydration progress continuously, such as SEM observation, residual quantity test for Ca(OH) 2 , and the rate of heat evolution. The results of the examinations indicate that the SiO 2 in nano scale behave not only as a filler to improve the microstructure, but also as an activator to promote pozzolanic reactions.
TL;DR: In this article, the corrosion behavior of steel in concrete, mortar, or in simulated pore solution is studied, and it is shown that steel needs to be kept at least three days in synthetic pore solutions and seven days in mortar to be passivated.
TL;DR: In this article, the effects of high temperature on the mechanical properties of cement-based mortars containing pumice and fly ash were investigated by using X-ray and SEM analyses.
TL;DR: In this article, the pore fluid of SRA-containing mortar has lower surface tension, which can result in lower crackinducing stresses at the mortar's topmost layer, reduced capillary tension, reduced settlement, and less evaporation.
Abstract: Cracking that forms between concrete placement and concrete setting is generally described as plastic shrinkage cracking The authors discuss how concave menisci may form on fresh concrete surfaces due to water evaporation Potential development of plastic shrinkage cracks may occur when concrete surface tensile stress and concrete settlement develop because of the menisci The authors focus on how mortars containing a shrinkage-reducing admixture (SRA), which is commercially available, develop plastic shrinkage cracks When exposed to the same environmental conditions, fewer and narrower plastic shrinkage cracks are shown in SRA-containing mortar than plain mortar The authors propose that pore fluid of SRA-containing mortar has lower surface tension, which can result in lower crack-inducing stresses at the mortar's topmost layer, reduced capillary tension, reduced settlement, and less evaporation
TL;DR: In this paper, the properties of brick masonry were studied using table-moulded bricks and wire-cut bricks of India with various types of mortars and various sizes of prisms and wallettes.
Abstract: The characteristics of brick masonry are influenced by the properties of bricks and mortar. This paper attempts at studying the properties of brick masonry using table moulded bricks and wire-cut bricks of India with various types of mortars. The strength and elastic modulus of brick masonry under compression have been evaluated for strong-brick soft-mortar and soft-brick strong-mortar combinations. Various sizes of prisms and wallettes have been tested during these experiments to study the size effect and different bonding arrangements. The failure mechanisms of such specimens have been studied. Attempts are also made to derive empirical relationships for masonry strength as a function of brick and mortar strength in the Indian context.
TL;DR: In this article, the pore structure and mechanical properties of lime-cement mortars are evaluated in order to analyze their potential use, because this kind of mortar could reduce the disadvantages presented by both lime-based and cement-based mortars.
TL;DR: In this article, the performance of manufactured fine aggregates produced by cone crushing or impact crushing has been compared to that of mortars prepared from a natural sand control-sample, and it was shown that the unclassified impact crusher product presented the highest packing density, and mortars produced from it had comparatively low porosity and low absorptivity and the highest unconfined compressive strength.
TL;DR: In this article, the diffusivity of chloride has been evaluated using mortar specimens, and concrete specimens were used to assess the durability performance related to inorganic coating materials via carbonation test and frost resistance test.
TL;DR: In this article, the authors investigated the effect of acid-silica reaction (ASR) on concrete paving blocks produced with partial replacement of natural aggregates by crushed glass cullet.
Abstract: There is a growing interest of using recycled crushed glass (RCG) as an aggregate in construction materials especially for non-structural applications. Although the recycled crushed glass is able to reduce the water absorption and drying shrinkage in concrete products due to its near to zero water absorption characteristics, the potential detrimental effect of using glass due to alkali–silica reaction (ASR) in cementitious materials is a real concern. The extent of ASR and its effect on concrete paving blocks produced with partial replacement of natural aggregates by crushed glass cullet are investigated in this study. This study is comprised of two parts. The first part quantified the extent of the ASR expansion and determined the adequate amount of mineral admixtures that was needed to reduce the ASR expansion for concrete paving blocks prepared with different recycled crushed glass contents using an accelerated mortar bar test in accordance with ASTM C 1260 (80 °C, 1 N NaOH solution). In the second part, concrete paving blocks were produced using the optimal mix proportion derived in the first part of this study and the corresponding mechanical properties were determined. It was found from the mortar bar test that the incorporation of 25% or less RCG induced negligible ASR expansion after a testing period of 28 days. For mixes with a glass content of higher than 25%, the incorporation of mineral admixtures such as pulverized fuel ash and metakaolin was able to suppress the ASR expansion within the stipulated limit but the results need to be confirmed by other test methods such as the concrete prism test. The study concluded that the optimal mix formulation for utilizing crushed waste glass in concrete paving blocks should contain at least 10% PFA by weight of the total aggregates used.
TL;DR: In this paper, the pitting corrosion behavior of reinforced steel in cement mortar has been studied by electrochemical noise analysis (ENA) method, the wavelet transform has been employed to analyze the EN data of reinforcing steel in mortar, and the energy distribution plot (EDP) is plotted.
TL;DR: In this paper, the durability of concrete and mortar, including aggregate of discarded car tires under environmental conditions, was evaluated using physical, mechanical, and durability experiments on mortar and concrete specimens and it was determined that in the regions where the environmental conditions are not harsh, use of concrete produced with 10% rubber aggregate is appropriate as it is e...
Abstract: This study aims at determining the durability of mortar and concrete, including aggregate of discarded car tires under environmental conditions. These conditions are freeze-thaw, seawater, and high temperature. Concrete specimens produced with a cement dosage of 300, a 0.5 water-cement ratio, and 0, 10, 20, and 30% rubber aggregate in volume, where the grain size is 1–4 mm instead of fine aggregate, and portland compose cement (CEM II/B 32.5) are used for freeze-thaw. The effect of seawater on specimens produced with 10, 20, 30, and 40% rubber aggregate in volume instead of sand was investigated. For specimens produced with 10, 20, and 30% rubber aggregate in volume, the effect of high temperature was investigated. During this research physical, mechanical, and durability experiments were performed on mortar and concrete specimens. As a result it was determined that in the regions where the environmental conditions are not harsh, use of concrete produced with 10% rubber aggregate is appropriate as it is e...
TL;DR: In this article, an accelerated corrosion test was carried out by impressing current between steel embedded in mortar and a counter-electrode to study the process of corrosion leading to cracking in mortar.
TL;DR: In this article, the authors used acoustic emission and X-ray tomography to identify the mechanisms of damage and the fracture process during compressive loading on concrete specimens, in relation with the microstructure of the material.
TL;DR: In this article, the effect of temperature on the ultimate strength of concrete bricks was evaluated by a new model, which satisfactorily predicts the strength at 28 and 90 days of the second set mortar.
Abstract: A first set of mortar specimens was made with 0%, 10%, 20%, 30% and 40% of natural pozzolan replacement and cured under constant curing temperature of 20, 40 and 60 °C with saturated humidity. The second set incorporating only 20% of natural pozzolan was exposed to elevated temperatures for 1, 3 and 7 days and then cured in saturated environment under a temperature of 20 °C. This paper presents the experimental results of the mortar properties such as the ultimate strength, the half age of strength and the activation energy. The introduction of the pozzolan enhances the ultimate compressive strengths and increases the activation energy which indicates the slow reactivity. The effect of the temperature on the ultimate strengths is evaluated by a new model. By using the equivalent time method, we could estimate the strength at 28 and 90 days of the second set mortar. This method satisfactorily predicts the strength of concrete cured at any temperature history.
TL;DR: Several methods have been proposed for rapid measurement of the liquid permeability of saturated cement paste, mortar and concrete as discussed by the authors, and some recent results obtained on pastes and mortars are presented.
TL;DR: In this article, the authors assess the mechanical properties of hollow concrete masonry using experimental results from prisms constructed with blocks of two different strengths and four types of mortar and conclude that mortar is mostly responsible for the non-linear behavior of masonry.
Abstract: The aim of this work is to critically assess the mechanical properties of hollow concrete masonry using experimental results from prisms constructed with blocks of two different strengths and four types of mortar. A key conclusion is that mortar is mostly responsible for the non-linear behavior of masonry. Moreover, a strongly non-linear relationship between masonry elasticity modulus and compressive strength is found, which contradicts the simple linear relation proposed by Eurocode 6 [CEN. Eurocode 6: Design of masonry structures – Part 1 – Common rules for reinforced and unreinforced masonry structures. EN-1996-1-1; 2005.]. The porosity of mortar and the state of stress that mortar undergoes in the process of compressive loading can be responsible for changes in the mechanical properties, such as elasticity modulus and Poisson’s ratio. Finally, different types of mortars induce different failure modes in the masonry prisms and there is clear evidence that the failure of hollow concrete masonry starts after onset of mortar crushing. In order to better reproduce the observed experimental behavior, a tentative model for the mortar Poisson’s ratio variation upon loading is also presented.
TL;DR: In this article, the compressive strength of cement mortar with the addition of silica fume was evaluated at various water-cementitious ratio, including 0.23, 0.25, 0, 32, 35, and 0.48, and four contents of nano-SiO2 particles, 3, 6, 9, and 12%.
Abstract: The nano scale of particles can result in dramatically improved or different properties from conventional grain-size materials of the same chemical composition. Therefore, it is practical to add nano-silica in particle form with 99.9% of SiO2 in nano scale to improve the characteristics of cement mortar. The compressive strengths of cement mortar were evaluated at various water-cementitious ratio. Five different water-cementitious ratios were used including, 0.23, 0.25, 0.32, 0.35, and 0.48 and four contents of nano-SiO2 particles, 3%, 6%, 9%, and 12% by weight of cement. The compressive strength of cement mortar with the addition of silica fume were also evaluated at w/cm ratio of 0.48 to compare with mortar containing nano-SiO2 particles and three contents of silica fume were: 5%, 10% and 15% by weight of cement. The experimental results show that the compressive strengths of mortars with nano-SiO2 particles were all higher than those of mortars containing silica fume at 7 and 28 days. It was demonstrated that the nano-particles were more valuable in enhancing strength than silica fume. This paper also analyzed some available examinations to monitor the hydration progress continuously, such as SEM observation, residual quantity test for Ca(OH)2 and the rate of heat evolution. The results of the examinations indicate that the SiO2 in nano scale behave not only as a filler to improve the microstructure, but also as an activator to promote pozzolanic reactions.
TL;DR: In this article, the Novosol® process is used for the treatment of polluted sediments, which is based on the stabilisation of heavy metals and on the thermal elimination of organic matter.
Abstract: The disposal of contaminated dredged material has become an economical and environmental issue. Firstly, this study presents the Novosol® process which was used for the treatment of polluted sediments. This process is based on the stabilisation of heavy metals and on the thermal elimination of organic matter. A physical characterization of the processed material reveals high porosity (60%) and water absorption (45%). Moreover, the treated sediment aggregate (TSA) has a relatively low strength and a high content of fine particles. Secondly, an experimental study on the feasibility of TSA introduction in cement-based materials was performed. Three mortars for which a given sand volume was replaced by the same sediment volume (33%, 66% and 100%) were designed. A strong increase of drying shrinkage was observed (up to 10 times higher, when compared to a reference mortar). Permeability remained virtually constant, though. There was a significant increase in strength for low to moderate substitution, while high incorporated quantity of sediment led to a strength on the same order of that of the reference mortar.
TL;DR: In this article, the textural aspects, porometry and hydric behaviour of combinations of building materials and their durability under attack by salt crystallisation and freezing were dealt with, and four types of lime mortar were selected.