Showing papers on "Mortar published in 2006"
TL;DR: In this article, results from experimental research carried out on certain engineering properties of a new (portland cement-free) concrete made with alkali-activated fly ash are reported.
Abstract: In this paper, results are reported from experimental research carried out on certain engineering properties of a new (portland cement-free) concrete made with alkali-activated fly ash Lab tests were conducted to determine its bending and compression mechanical strength, modulus of elasticity, bond strength, and shrinkage The results show that mortar and concrete made with portland cement-free activated fly ash develop a high mechanical strength in short periods of time, have a moderate modulus of elasticity, bond better to reinforcing steel, and shrink much less than ordinary portland cement concrete
403 citations
TL;DR: In this article, the carbonation of fly ash concrete is studied by using two types of Fly Ash with different CaO contents, and it is observed that under natural exposure environments, the Carbonation rate is the highest when specimens are exposed in the city.
292 citations
TL;DR: In this article, the authors evaluated the effectiveness of various mineral additives and chemical admixtures in producing self-compacting concrete (SCM) and concluded that fly ash and limestone powder significantly increased the workability of SCM.
Abstract: Mortar serves as the basis for the workability properties of self-compacting concrete (SCC) and these properties could be assessed by self-compacting mortars (SCM). In fact, assessing the properties of SCM is an integral part of SCC design. The objective of this study was to evaluate the effectiveness of various mineral additives and chemical admixtures in producing SCMs. For this purpose, four mineral additives (fly ash, brick powder, limestone powder, and kaolinite), three superplasticizers (SP), and two viscosity modifying admixtures (VMA) were used. Within the scope of the experimental program, 43 mixtures of SCM were prepared keeping the amount of mixing water and total powder content (portland cement and mineral additives) constant. Workability of the fresh mortar was determined using mini V-funnel and mini slump flow tests. The setting time of the mortars, were also determined. The hardened properties that were determined included ultrasonic pulse velocity and strength determined at 28 and 56 days. It was concluded that among the mineral additives used, fly ash and limestone powder significantly increased the workability of SCMs. On the other hand, especially fly ash significantly increased the setting time of the mortars, which can, however, be eliminated through the use of ternary mixtures, such as mixing fly ash with limestone powder. The two polycarboxyl based SPs yield approximately the same workability and the melamine formaldehyde based SP was not as effective as the other two.
292 citations
01 Jan 2006
286 citations
TL;DR: In this article, optical microscopy is also used for damage diagnosis of degraded historic mortars and for the study of the interfacial zone, the bonding and possible reaction rims between aggregates, bricks or stone and the mortar.
282 citations
TL;DR: In this paper, a simple model is proposed to relate ultrasonic pulse velocity with porosity and permeability, and experimental results are shown and correlations between the measured parameters of the material are discussed.
269 citations
TL;DR: In this paper, the behavior of waterglass- or NaOH-activated slag mortars after carbonation was analyzed and the effect of a superplasticizer based on vinyl copolymer and shrinkage reducing polypropylenglycol derivative admixtures on that process was examined.
Abstract: This study analyzes the behaviour of waterglass- or NaOH-activated slag mortars after carbonation. The effect of a superplasticizer based on vinyl copolymer and shrinkage reducing polypropylenglycol derivative admixtures on that process was also examined. The same tests were run on cement mortars for reference purposes. The mortars were carbonated in a chamber ensuring CO2 saturation for four and eight months, after which ages the samples were tested for mechanical strength; mercury porosimetry and mineralogical (XRD, FTIR) and microstructural characterization (SEM/EDX) were also conducted. The results obtained indicate that alkali-activated slag mortars were more intensely and deeply carbonated than Portland cement mortars. Carbonation took place directly on the gel, causing decalcification. When waterglass was the alkaline activator used, carbonation caused a loss of cohesion in the matrix and an important increase in porosity and decrease in mechanical strength. When a NaOH solution was used as the alkali activator, carbonation enhanced mortar compaction and increased mechanical strength. Finally, in waterglass-activated slag mortars, the inclusion of organic admixtures had no effect either on their behaviour after carbonation or the nature of the reaction products.
248 citations
TL;DR: In this article, a buckling-restrained brace can be formed by welding a core plate covered with unbonded material to a pair of mortar-filled channel steels as a restraining part.
Abstract: The authors developed a buckling-restrained brace that enables increased design freedom at both ends of the core plate and strict quality control while providing stable hysteresis characteristics even under high strains. The buckling-restrained brace can be formed by welding a core plate covered with unbonded material to a pair of mortar-filled channel steels (steel mortar planks) as a restraining part. The use of this approach enables visual confirmation of the status of the mortar filling and also facilitates standardizing structural members and member-by-member quality control. Specimens of a buckling-restrained brace with different steel mortar plank heights are fabricated to adjust the restraining force, along with specimens with different core plate width-to-thickness ratios. The tests were conducted to reveal the hysteretic characteristics of the braces, as well as their cumulative plastic strain energy, elastoplastic properties, and stiffening properties. A performance evaluation formula as well as a buckling-restrained brace design method using the test results is proposed. Copyright © 2006 John Wiley & Sons, Ltd.
196 citations
TL;DR: In this article, the microstructure of recycled aggregate concrete was analyzed using a fluorescent light optical microscope, which made it possible to observe the high porosity of recycled aggregates with and without adhered mortar.
Abstract: Fifty percent of the total weight of construction and demolition waste is concrete. Consequently, the utilisation of crushed waste concrete must be considered as imperative in concrete production. Recycled aggregates are formed basically by adhered mortar and original aggregates. Adhered mortar is a very porous material, with a high absorption capacity and high permeability. Four different percentages (0, 25, 50 and 100%) of wet recycled coarse aggregates were used in the production of the concrete tested, the same compressive strength being obtained in all four mixes. The microstructure of recycled aggregate concrete was analysed using a fluorescent light optical microscope, which made it possible to observe the high porosity of recycled aggregates with and without adhered mortar, the increment of air void percentage in new cement paste when high amounts of recycled aggregates are used and the effectiveness of new interfacial transition zone in recycled aggregate concrete.
182 citations
TL;DR: In this paper, the authors presented the characterization of microstructural evolution in a mortar subjected to a chemical attack, by means of a powerful non-intrusive experimental method, namely synchrotron X-ray computed microtomography.
166 citations
TL;DR: In this paper, a penalty formulation based on the mortar concept for two-dimensional large deformation frictional contact is presented, which can be used within a quadratic approximation of the solid elements.
TL;DR: In this paper, an adequate number of mortar series were prepared and tested to find the effect of water/binder (w/b) ratio, the aggregate volume content, the evolution of porosity with time and formulate the strength-porosity relationship based on Power's basic mathematical expression.
TL;DR: In this paper, the decrease in strength of tile adhesives during wet storage was investigated, and it was observed that cellulose ether and polyvinyl alcohol structures are water-soluble.
TL;DR: In this paper, the authors present an overview of some of the research published on the use of CKD in cement paste/mortar/concrete, and their effect on the CKD properties like compressive strength, tensile strength properties, durability, hydration, setting time, sorptivity, electrical conductivity are presented.
Abstract: Solid waste management is one of the major environmental concerns around the world. Cement kiln dust (KKD), also known as by-pass dust, is a by-product of cement manufacturing. The environmental concerns related to Portland cement production, emission and disposal of CKD is becoming progressively significant. CKD is fine-grained, particulate material chiefly composed of oxidized, anhydrous, micron-sized particles collected from electrostatic precipitators during the high temperature production of clinker. Cement kiln dust so generated is partly reused in cement plant and landfilled. The beneficial uses of CKD are in highway uses, soil stabilization, use in cement mortar/concrete, CLSM, etc. Studies have shown that CKD could be used in making paste/mortar/concrete. This paper presents an overview of some of the research published on the use of CKD in cement paste/mortar/concrete. Effect of CKD on the cement paste/mortar/concrete properties like compressive strength, tensile strength properties (splitting tensile strength, flexural strength and toughness), durability (Freeze–thaw), hydration, setting time, sorptivity, electrical conductivity are presented. Use of CKD in making controlled low-strength materials (CLSM), asphalt concrete, as soil stabilizer, and leachate analysis are also discussed in this paper.
TL;DR: In this article, the influence of rubber aggregates on the load-deflection relationship of mortar in flexure was investigated and the synergy between rubber aggregate substitution and metal-fibre reinforcement was also investigated.
TL;DR: In this paper, the carbonation profile of material taken at various depths in a lime mortar specimen has been determined at different times from manufacture using a novel, high-speed thermogravimetric analysis (TGA) method.
TL;DR: In this paper, a set of mortars consisting of air-hardening lime with a progressively increasing cement content, as well as a mortar containing hydraulic lime were used to investigate the pore structure of lime-based mortars.
TL;DR: The results of the tests indicate that desert sand can be used as a fine aggregate in mortar and concrete for general civil engineering as mentioned in this paper, which indicates that sand can also be applied as fine aggregate for concrete.
TL;DR: In this paper, the effects of water-retaining admixture on the rheological properties of a cement-based render mortar were studied with a rheometer for mortars using two different speed profiles.
TL;DR: In this article, the results of an investigation of the properties of mortar in which a calcined clay was employed as a pozzolan were presented, and the compressive strengths of the mortars were monitored up to 90 days and the resistance to sodium sulphate solution and synthetic seawater was monitored for up to 300 days.
Abstract: This paper presents the results of an investigation of the properties of mortar in which a calcined clay was employed as a pozzolan. Mortars were prepared using either heat treated clay or ground waste clay bricks (from the same clay subjected to 1000 °C calcining) as a pozzolanic partial replacement for cement at replacement levels of 10%, 20% and 30%. The compressive strengths of the mortars were monitored up to 90 days and the resistance to sodium sulphate solution and synthetic seawater was monitored up to 300 days. The specimens were also monitored for weight changes. Partially replacing cement by ground brick or heat-treated brick clay gives early strengths that are lower than that of the control. At 90 days, however, the strengths are the same as or are greater than that of the control. Heat-treated clay is effective in reducing expansion during exposure of the mortar to sulphate solution and synthetic seawater. The rapidly cooled clay gives better performance, in terms of strength development and resistance to harmful solutions, than the slow cooled clay.
TL;DR: In this article, a comparative study was carried out of several mortars, in some cases using different additions of silica fume or activated fly ash, and the influence that these additives have on the mechanical resistance of the mortars was studied.
TL;DR: In this article, the influence of chloride ingress on mortar microstructure (including microstructural alterations of hydration products and of pore structure) has been studied by the authors on the basis of cross-section image analysis of reinforced mortar specimens.
TL;DR: In this article, the effect of level of addition of natural pozzolana (0, 10, 20, 30, and 40%) on the mechanical properties of mortars at different ages was investigated.
Abstract: This paper presents a study of the properties and behaviour of cement mortar with natural pozzolana from Algeria. The effect of level of addition of natural pozzolana (0, 10, 20, 30, and 40%) on the mechanical properties of mortars at different ages as well as the effect of curing environment and the period of initial curing on the mechanical properties were investigated. The performance of natural pozzolana cement exposed to three aggressive solutions (acids, sulphate, and chloride) is also analysed. The results indicate that the strength of pozzolanic cement is lower than that of plain Portland cement at early ages, but can reach the same order of strength at longer curing periods. The enhancement of the resistance to acid and sulphate attack as well as to chloride ion penetration of natural pozzolanic cement is also demonstrated.
TL;DR: In this article, the porosity and strength of OPC pastes with 10% to 40% mineral additives, such as steel-making slag, granulated blast furnace slag and fly ash, were determined at 3, 7, 28, 90 and 180 days.
TL;DR: In this article, the authors used cylindrical mortar specimens produced with a ram extruder to investigate the transition of the mortar from plastic and deformable to hardened state, and wave transmission and reflection measurements with P- and S-waves were conducted to obtain further information about the microstructural changes during the setting and hardening process.
Journal Article•
TL;DR: An attempt has been made to develop bioconcrete material incorporating of an enrichment culture of thermophilic and anaerobic bacteria within cement-sand mortar/concrete, showing a significant increase in compressive strength of both cement- sand mortar and concrete.
Abstract: In the biosphere, bacteria can function as geo-chemical agents, promoting the dispersion, fractionation and/or concentration of materials. Microbial mineral precipitation is resulted from metabolic activities of microorganisms. Based on this biomineralogy concept, an attempt has been made to develop bioconcrete material incorporating of an enrichment culture of thermophilic and anaerobic bacteria within cement-sand mortar/concrete. The results showed a significant increase in compressive strength of both cement-sand mortar and concrete due to the development of filler material within the pores of cement sand matrix. Maximum strength was observed at concentration 10(5)cell/ml of water used in mortar/concrete. Addition of Escherichia coil or media composition on mortar showed no such improvement in strength.
TL;DR: In this article, the shape memory alloys were used for concrete prestressing, and three-point bending tests were performed for the mechanical properties of the resulting concrete bricks, and it was found that prestressing increased the bending strength and cracking stress of the bricks.
Abstract: This article reports the mechanical properties of concrete prestressed by the Fe–Mn–Si-based shape memory alloys containing NbC that exhibit an excellent shape memory effect without the so-called ‘training’ treatment. A thermomechanically treated Fe–28Mn–6Si–5Cr–0.53Nb– 0.06C (mass%) alloy was used for this purpose. Four square bars of the alloy were embedded in mortar, and heated above their reverse martensitic transformation start temperature after hardening of the mortar matrix. Three-point bending tests were performed for the mechanical property characterization. It was found that prestressing by the shape memory alloys increased the bending strength and cracking stress of the mortar.
TL;DR: In this paper, the impact of a protein additive (powdered red blood cells) on selected physical properties of cement paste, fresh mortar and physical and mechanical properties of hardened mortar is described.
Abstract: Test results presented in the article describe the impact of a protein additive (powdered red blood cells) on selected physical properties of cement paste, fresh mortar and physical and mechanical properties of hardened mortar. The protein additive is achieved as a result of industrial processing of animal blood. The research was made in the laboratory of the Institute of Structural Engineering of Poznan University of Technology. The analysis of the test results achieved showed that the protein included in the preparation added to the mortar leads to intensive air entraining, which has a significant effect on the most basic of physical properties both of the fresh mortar (consistence, plasticity, volumetric density) and hardened mortar (bending strength, shrinkage, volumetric density and frost resistance). The intensity of this influence, calculated in relation to the mass of the protein preparation added to the mortar, for most of the tested properties, is much higher than in the case of currently used air entraining agents [Chatterji S. Freezing of air-entrained cement-based materials and specific actions of air-entraining agents. Cem Concr Compos 2003;25:759–65, Du Lianxiang, Folliard KJ. Mechanisms of air entrainment in concrete. Cem Concr Res 2005;35:1463–71, Neville AM. Properties of concrete. 4th and final ed. London: Longman Group Limited, 1995. p. 844].
TL;DR: In this article, the effect of factors such as dosage, curing conditions and use of a superplasticiser admixture on the porosity, mechanical strength and composition of slaked lime (SL)-metakaolin (MK) mortars was determined.
Abstract: The purpose of the present study is to determine the effect of factors such as dosage, curing conditions and use of a superplasticiser admixture on the porosity, mechanical strength and composition of slaked lime (SL)–metakaolin (MK) mortars. Statistical correlations have been established to describe the mechanical properties as well as porosity and composition of the slaked lime–metakaolin mortars. The SL/MK ratio has a moderate effect on mortar flexural and compressive strengths. The SL + MK/sand ratio is the factor with the highest impact on all the properties studied: strength, porosity and mortar composition. As this ratio increases, strength, porosity and amount of hydration and carbonation products formed in the samples also rise. The next factor by order of importance is the presence of a superplasticiser admixture, which affects porosity, strength and the amount of calcite in the sample. The presence of this superplasticiser admixture increases strength, raises the percentage of calcite in the mortars and reduces porosity. It is particularly striking that neither curing nor open air carbonation time (in the range studied) has a significant effect on the composition or porosity of the SL–MK mortars studied, although they do have a moderate effect on mechanical strength.
01 Jan 2006
TL;DR: In this article, the role of sulphate ions in causing deterioration of concrete has been investigated intensively, with particular attention to the use of blended cement in recent times with the influences of the parameters related to the Sulphate resistance of cement concrete and mortar.
Abstract: Cement concrete continues to be the pre-eminent construction materials for use in any type of civil engineering structure. Performance of these structures in terms of their strength and stability has withstood the test of time but the life span of the structures has become a matter of concern. This is on account of the environment becoming chemically ever more aggressive. The atmosphere is found increasingly laden with higher percentages of Sulfur Dioxide, Carbon Dioxide and Chlorides. Oxides of Sulfur are injurious to concrete while Chlorides are harmful to the reinforcing steel. As a consequence of these, the life-span of the reinforced concrete structures have got compromised significantly from its original estimated life of about ninety years. The role of Sulphate ions in causing deterioration of concrete has been investigated intensively. Based on the literature available, the present paper discusses this aspect with particular attention to the use of blended cement in recent times with the influences of the parameters related to the Sulphate resistance of cement concrete and mortar.