Effect of mortar properties on strength of masonry /

"Issued November 20, 1961."

Properties of Mortar Using Cubes, Prism Halves, and Cylinder Specimens

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biomass fly ash incorporation in cement based materials

In recent years, pressures on global environment and energy security have led to an increasing demand on renewable energy sources, and diversification of Europe’s energy supply. Among these resources the biomass could exert an important role, since it is considered a renewable and CO2 neutral energy resource once the consumption rate is lower than the growth rate, and can potentially provide energy for heat, power and transports from the same installation. Currently, most of the biomass ash produced in industrial plants is either disposed of in landfill or recycled on agricultural fields or forest, and most times this goes on without any form of control. However, considering that the disposal cost of biomass ashes are raising, and that biomass ash volumes are increasing worldwide, a sustainable ash management has to be established. The main objective of the present study is the effect of biomass fly ashes in cement mortars and concretes in order to be used as a supplementary cementitious material. The wastes analyzed in the study were collected from the fluidized bed boilers and grate boilers available in the thermal power plants and paper pulp plants situated in Portugal. The physical as well as chemical characterisations of the biomass fly ashes were investigated. The cement was replaced by the biomass fly ashes in 10, 20 and 30% (weight %) in order to investigate the fresh properties as well as the hardened properties of biomass fly ash incorporated cement mortar and concrete formulations. Expansion reactions such as alkali silica reaction (ASR), sulphate attack (external and internal) were conducted in order to check the durability of the biomass fly ash incorporated cement mortars and concretes. Alternative applications such as incorporation in lime mortars and alkali activation of the biomass fly ashes were also attempted. The biomass fly ash particles were irregular in shape and fine in nature. The chemical characterization revealed that the biomass fly ashes were similar to a class C fly ash. The mortar results showed a good scope for biomass fly ashes as supplementary cementitious materials in lower dosages (<20%). The poor workability, concerns about the organic content, alkalis, chlorides and sulphates stand as the reasons for preventing the use of biomass fly ash in high content in the cement mortars. The results obtained from the durability tests have shown a clear reduction in expansion for the biomass fly ash mortars/concretes and the binder blend made with biomass fly ash (20%) and metakaolin (10%) inhibited the ASR reaction effectively. The biomass fly ash incorporation in lime mortars did not improve the mortar properties significantly though the carbonation was enhanced in the 15-20% incorporation. The biomass fly ash metakaolin blend worked well in the alkali activated complex binder application also. Portland cement free binders (with 30-40 MPa compressive strength) were obtained on the alkali activation of biomass fly ashes (60-80%) blended with metakaolin (20-40%).

Síntese, aplicação e avaliação do efeito do teor de fósforo da celulose fosfatada em argamassa de alvenaria com aditivo comercial a base de hidroxi-etil-metil celulose (HEMC)

Generally, cellulose ethers improves mortar properties such as water retention, workability and setting time, along with adherence to the substrate. However, a major disadvantage of the addition of cellulose ethers in mortars is the delay in hydration of the cement. In this paper a cellulose phosphate (Cp) was synthesized water soluble and has been evaluated the effect of their incorporation into mortar based on Portland cement. Cellulose phosphate obtained was characterized by spectrophotometry Fourier transform infrared (FTIR), X-ray diffraction (XRD), elemental analysis and scanning electron microscopy (SEM). Mortar compositions were formulated with varying phosphorus content in cellulose and cellulose phosphate concentrations, when used in partial or total replacement of the commercial additive based hydroxyethyl methyl cellulose (HEMC). The mortars formulated with additives were prepared and characterized by: testing in the fresh state (consistency index, water retention, bulk density and air content incorporated) and in the hardened state (absorption by capillarity, density, flexural and compression strength). In mixtures the proportion of sand:cement of 1:5 (v / v) and factor a / c = 1.31 and water were held constant. Overall, the results showed that the celluloses phosphates employed in mortars added acted significantly when partially substituting the commercial additive. With regard to consistency index, water retention and bulk density in the fresh state and absorption by capillarity and bulk density apparent in the hardened state, showed no appreciable differences as compared to the commercial additive. The incorporated air content in the fresh state reduced markedly, but did not affect other properties. The mortars with cellulose phosphate, partially replacing the commercial additive showed an improvement of the properties of flexural strength and compressive strength

Desenvolvimento de argamassa para restauração utilizando resíduo do polimento do porcelanato

The coatings mortars are essential elements of building structures because they execute an important role in protecting walls and are particularly exposed to aggressive action responsible for its degradation over time. The importance of wall coverings has been the subject of discussion and analysis in the conservation and rehabilitation of old buildings. Are sometimes removed and replaced with inappropriate solutions of constructive point of view or architecture. The most commonly used coatings on walls of old buildings is based on traditional hydraulic lime mortars. The present study aims at the formulation of new lime- based mortars and aerial fine aggregate, in order to contribute to a better field of conservation and restoration mortar coating of old buildings. Residue was used for polishing porcelain as fine aggregate, replacing the aggregate (sand), in percentages 05-30% by mass. We conducted a thorough evaluation of the mortar properties in fresh and hardened state by comparing the performance of the same with a reference mortar. The residue used was characterized as the density, bulk density, and particle size laser, scanning electron microscopy, X-ray diffraction and X-ray fluorescence. Formulations were produced 7, 6 with residue and one commonly used formulation, which served as a reference. In the formulations of lime mortars air (hydrated lime powder CH-I) has been adopted a stroke volume (1:3) with constant binder, was varied and the water / binder and aggregate and waste. For evaluation of mortars fresh, proceeded to consistency analysis, specific gravity, water retention and air content embedded. In the hardened state assays were performed in specific gravity, water retention, modulus of elasticity, tensile strength in bending, compressive strength, water absorption by capillary action, adhesion, tensile strength, resistance to shrinkage and salts by of crystallization trials with resources chloride solution, nitrate and sulfate all sodium in prismatic at 90 days of age, in addition to the micro structural analysis of mortars. Based on the results we can see that the mortar formulated with 10% content of waste and the reference free retraction feature more stable closer to neutrality. The composition of 10% was obtained better performance against the action of the salt crystallization. The mortar with 15% residue obtained better density, lower air content embedded and high capacity for water retention developing good workability. The replacement of 20% of waste generates a satisfactory utilization of resistance to compression, flexion and traction grip the base. And, finally, it can be seen that the mortar with 10, 15 and 20% residual show, in principle, good suitability as coatings, thus enabling a final result consistent with durability, workability and aesthetics developing therefore a material with better performance to repair or replace existing mortars in old buildings

Síntese, aplicação e avaliação do efeito do teor de fósforo da celulose fosfatada em argamassa de alvenaria com aditivo comercial a base de hidroxi-etil-metil celulose (HEMC)

Generally, cellulose ethers improves mortar properties such as water retention, workability and setting time, along with adherence to the substrate. However, a major disadvantage of the addition of cellulose ethers in mortars is the delay in hydration of the cement. In this paper a cellulose phosphate (Cp) was synthesized water soluble and has been evaluated the effect of their incorporation into mortar based on Portland cement. Cellulose phosphate obtained was characterized by spectrophotometry Fourier transform infrared (FTIR), X-ray diffraction (XRD), elemental analysis and scanning electron microscopy (SEM). Mortar compositions were formulated with varying phosphorus content in cellulose and cellulose phosphate concentrations, when used in partial or total replacement of the commercial additive based hydroxyethyl methyl cellulose (HEMC). The mortars formulated with additives were prepared and characterized by: testing in the fresh state (consistency index, water retention, bulk density and air content incorporated) and in the hardened state (absorption by capillarity, density, flexural and compression strength). In mixtures the proportion of sand:cement of 1:5 (v / v) and factor a / c = 1.31 and water were held constant. Overall, the results showed that the celluloses phosphates employed in mortars added acted significantly when partially substituting the commercial additive. With regard to consistency index, water retention and bulk density in the fresh state and absorption by capillarity and bulk density apparent in the hardened state, showed no appreciable differences as compared to the commercial additive. The incorporated air content in the fresh state reduced markedly, but did not affect other properties. The mortars with cellulose phosphate, partially replacing the commercial additive showed an improvement of the properties of flexural strength and compressive strength

Desenvolvimento de argamassa para restauração utilizando resíduo do polimento do porcelanato

The coatings mortars are essential elements of building structures because they execute an important role in protecting walls and are particularly exposed to aggressive action responsible for its degradation over time. The importance of wall coverings has been the subject of discussion and analysis in the conservation and rehabilitation of old buildings. Are sometimes removed and replaced with inappropriate solutions of constructive point of view or architecture. The most commonly used coatings on walls of old buildings is based on traditional hydraulic lime mortars. The present study aims at the formulation of new lime- based mortars and aerial fine aggregate, in order to contribute to a better field of conservation and restoration mortar coating of old buildings. Residue was used for polishing porcelain as fine aggregate, replacing the aggregate (sand), in percentages 05-30% by mass. We conducted a thorough evaluation of the mortar properties in fresh and hardened state by comparing the performance of the same with a reference mortar. The residue used was characterized as the density, bulk density, and particle size laser, scanning electron microscopy, X-ray diffraction and X-ray fluorescence. Formulations were produced 7, 6 with residue and one commonly used formulation, which served as a reference. In the formulations of lime mortars air (hydrated lime powder CH-I) has been adopted a stroke volume (1:3) with constant binder, was varied and the water / binder and aggregate and waste. For evaluation of mortars fresh, proceeded to consistency analysis, specific gravity, water retention and air content embedded. In the hardened state assays were performed in specific gravity, water retention, modulus of elasticity, tensile strength in bending, compressive strength, water absorption by capillary action, adhesion, tensile strength, resistance to shrinkage and salts by of crystallization trials with resources chloride solution, nitrate and sulfate all sodium in prismatic at 90 days of age, in addition to the micro structural analysis of mortars. Based on the results we can see that the mortar formulated with 10% content of waste and the reference free retraction feature more stable closer to neutrality. The composition of 10% was obtained better performance against the action of the salt crystallization. The mortar with 15% residue obtained better density, lower air content embedded and high capacity for water retention developing good workability. The replacement of 20% of waste generates a satisfactory utilization of resistance to compression, flexion and traction grip the base. And, finally, it can be seen that the mortar with 10, 15 and 20% residual show, in principle, good suitability as coatings, thus enabling a final result consistent with durability, workability and aesthetics developing therefore a material with better performance to repair or replace existing mortars in old buildings

Influence of Joint Thickness and Mortar-Block Elastic Properties on the Strength and Stresses Developed in Soil-Cement Block Masonry

Soil-cement blocks are employed for load bearing masonry buildings. This paper deals with the study on the influence of bed joint thickness and elastic properties of the soil-cement blocks, and the mortar on the strength and behavior of soil-cement block masonry prisms. Influence of joint thickness on compressive strength has been examined through an experimental program. The nature of stresses developed and their distribution, in the block and the mortar of the soil-cement block masonry prism under compression, has been analyzed by an elastic analysis using FEM. Influence of various parameters like joint thickness, ratio of block to mortar modulus, and Poisson's ratio of the block and the mortar are considered in FEM analysis. Some of the major conclusions of the study are: (1) masonry compressive strength is sensitive to the ratio of modulus of block to that of the mortar (Eb/Em) and masonry compressive strength decreases as the mortar joint thickness is increased for the case where the ratio of block to mortar modulus is more than 1; (2) the lateral tensile stresses developed in the masonry unit are sensitive to the Eb/Em ratio and the Poisson's ratio of mortar and the masonry unit; and (3) lateral stresses developed in the masonry unit are more sensitive to the Poisson's ratio of the mortar than the Poisson's ratio of the masonry unit.

Dynamic mechanical properties for polyurethane elastomers applied in elastomeric mortar

Dynamic mechanical properties of a polyurethane (PU) elastomer and a mortar processed with the same elastomer (modified polytetramethylene ether glycol (PTMEG)) were studied. The results obtained showed that the liquid aromatic amine ETHACURE (R) 300, used as cure agent, can be used to substitute the aromatic amine MOCA (R), which is usually used as cure agent in high performance elastomers. The resulting mortar produced with ETHACURE (R) 300 presents similar dynamic-mechanical thermal properties when compared with MOCA (R). However, dynamic-mechanical thermal analysis studies showed that the mortar developed with ETHACURE (R) 300 presents some advantages such as the low values of tan d, indicating a good capacity of recovery of the strain after retreating an applied force. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Influence of interface properties on fracture behaviour of concrete

Hardened concrete is a three-phase composite consisting of cement paste, aggregate and interface between cement paste and aggregate. The interface in concrete plays a key role on the overall performance of concrete. The interface properties such as deformation, strength, fracture energy, stress intensity and its influence on stiffness and ductility of concrete have been investigated. The effect of composition of cement, surface characteristics of aggregate and type of loading have been studied. The load-deflection response is linear showing that the linear elastic fracture mechanics (LEFM) is applicable to characterize interface. The crack deformation increases with large rough aggregate surfaces. The strength of interface increases with the richness of concrete mix. The interface fracture energy increases as the roughness of the aggregate surface increases. The interface energy under mode II loading increases with the orientation of aggregate surface with the direction of loading. The chemical reaction between smooth aggregate surface and the cement paste seems to improve the interface energy. The ductility of concrete decreases as the surface area of the strong interface increases. The fracture toughness (stress intensity factor) of the interface seems to be very low, compared with hardened cement paste, mortar and concrete.

Effect of nanosilica addition on the fresh properties and shrinkage of mortars with fly ash and superplasticizer

The ongoing use of various mineral additions along with chemical admixtures such as superplasticizers justifies the need for further research. Understanding and quantifying their effects and possible synergies on the fresh and hardened properties of cement-based materials is necessary, especially if some of these components are known to have a pozzolanic effect. This paper describes and models the fresh and hardened properties of cement mortars including nanosilica and fly ash, and relates their properties to the proportioning of these materials and the superplasticizer dosage. Mini-slump, Marsh cone and Lombardi cone tests were used to examine the properties of the fresh mortars, and to assess density, plastic shrinkage, and drying shrinkage up to 20 days. The equations presented in this paper make it possible to optimize mortar proportionings to the required levels of performance in both fresh and hardened states.

An experimental evaluation of prediction models for the mechanical behavior of unreinforced, lime-mortar masonry under compression

This paper contributes to the understanding of lime-mortar masonry strength and deformation (which determine durability and allowable stresses/stiffness in design codes) by measuring the mechanical properties of brick bound with lime and lime-cement mortars. Based on the regression analysis of experimental results, models to estimate lime-mortar masonry compressive strength are proposed (less accurate for hydrated lime (CL90s) masonry due to the disparity between mortar and brick strengths). Also, three relationships between masonry elastic modulus and its compressive strength are proposed for cement-lime; hydraulic lime (NHL3.5 and 5); and hydrated/feebly hydraulic lime masonries respectively.

Disagreement between the experimental results and former mathematical prediction models (proposed primarily for cement masonry) is caused by a lack of provision for the significant deformation of lime masonry and the relative changes in strength and stiffness between mortar and brick over time (at 6 months and 1 year, the NHL 3.5 and 5 mortars are often stronger than the brick). Eurocode 6 provided the best predictions for the compressive strength of lime and cement-lime masonry based on the strength of their components. All models vastly overestimated the strength of CL90s masonry at 28 days however, Eurocode 6 became an accurate predictor after 6 months, when the mortar had acquired most of its final strength and stiffness.

The experimental results agreed with former stress-strain curves. It was evidenced that mortar strongly impacts masonry deformation, and that the masonry stress/strain relationship becomes increasingly non-linear as mortar strength lowers. It was also noted that, the influence of masonry stiffness on its compressive strength becomes smaller as the mortar hydraulicity increases.

Design of experiments applied to the mix design process of polymer mortar materials modified with GFRP recyclates

In this work, the effect of incorporation of recycled glass fibre reinforced plastics (GFRP) waste materials, obtained by means of shredding and milling processes, on mechanical behavior of polyester polymer mortar (PM) materials was assessed. For this purpose, different contents of GFRP recyclates (between 4% up to 12% in mass), were incorporated into polyester PM materials as sand aggregates and filler replacements. The effect of silane coupling agent addition to resin binder was also evaluated. Applied waste material was proceeding from the shredding of the leftovers resultant from the cutting and assembly processes of GFRP pultrusion profiles. Currently, these leftovers, jointly with unfinished products and scrap resulting from pultrusion manufacturing process, are landfilled, with supplementary added costs. Thus, besides the evident environmental benefits, a viable and feasible solution for these wastes would also conduct to significant economic advantages. Design of experiments and data treatment were accomplish by means of full factorial design approach and analysis of variance ANOVA. Experimental results were promising toward the recyclability of GFRP waste materials as aggregates and reinforcement for PM materials, with significant improvements on mechanical properties with regard to non-modified formulations.

Mortar added by tyre rubber residues: Characterisation in fresh and hardened state

Due to the progressive increase of vehicles, the number of used tires is globally one of the serious environmental problems faced now. Therefore, several researches have being developed for its reuse. The use of tires' rubber in the concrete is a possible form of its application, aiming at the recycling of this material and the improvement of certain properties, as tenacity, impact resistance, thermal and acoustic isolation. This article presents conclusions that several researchers obtained using the rubberized concrete. Thus there were researched several works enclosing the period of 1993 to 2003, presenting then the results of some characteristics of this concrete such as: physical properties in fresh and hardened state, mechanical properties and properties that remit the durability. The bibliographical revision has as objective to subsidize future researches that can contribute to improve the use of this concrete in civil construction.