Tensile Strength Of Mortar Research Articles

Stochastic fracture of concrete composites: A mesoscale methodology

The accurate prediction of concrete composites’ fracture behaviour requires precise meso-structural characterization, appropriate fracture modelling, and pivotal uncertainty assessment. Towards this goal, we adopt a dynamics approach with CT images to generate numerical concrete models using real aggregates with 30%-60% contents. An image slicing method is then developed to obtain a large number of realistic models in 2D, whose heterogeneity is characterised by aggregates, mortar and interfaces. Monte Carlo simulations of uniaxial tension are performed, incorporating cross-scale fracture evolution through a phase-field cohesive zone model. Statistical analyses reveal that the stochasticity of crack patterns and stress-displacement curves, especially post-peak softening responses, is inherently dependent on the random meso-structures. It is observed that increasing aggregate content accelerates the deterioration rate of peak stress, decreases the softening curve, and leads to more tortuous crack paths, considering the ITZ crack channels. On the other hand, the tensile strength of mortar has significant impacts on the load-carrying capacity, while the fracture energy primarily influences the ductility and has negligible effects on the peak stress and the pre-peak nonlinear part. Besides, the ratios of mortar-ITZ tensile strength and fracture energy are found to affect the crack paths. The proposed numerical framework holds promise to reveal complex fracture mechanisms of concrete with more insights into other loading or environmental conditions.

Dynamic enhancing effect of free water on the dynamic tensile properties of mortar

This study investigates free water effect on the dynamic tensile properties of mortar. Fully saturated and saturated-then-redried mortar specimens with two porosities, namely common and high-porosity, are prepared and tested under quasi-static and dynamic split-tension states covering strain rates between 1.49e−06s−1 and 5.29s−1. The split-tensile strength and elastic modulus at different strain rates are quantified. Comparing the dynamic increase factor (DIF) for mortar tensile strength, a maximum difference of 1.2 at strain rate 5 s−1 is found between saturated and dried high-porosity mortars revealing the influence of free water. The testing data is compared with other existing data which shows the mortar water effect is more similar to concrete than limestone and sandstone. The high-speed camera images during the dynamic tests are analysed which revealed a water retarding effect on the dynamic split-tension failure process, resulting in an initial crack delay of up to 0.4 ms due to free water. The wave speed for different mortar specimens at different strain rates is analysed, which shows that higher porosity is more sensitive to the water effect. Possible mechanisms leading to this water effect is discussed. Overall, the study provides a quantitative measure of the water enhancing effect on the dynamic tensile strength of mortar and offers insights into the practical use of water in the design and construction of mortar structures.

Microstructure, tensile strength and shear strength of aggregate-mortar interface: Effect of aggregate mineralogy

This work aims to study the mechanical properties of the interfacial transition zone (ITZ) through both experimental tests and microstructural observations. The study considers a mortar with water-cement ratio of 0.58 and four types of aggregates: sandstone, granite, and two different types of limestone with varying water absorption coefficients. Chemical compositions, physical characteristics, and surface micromorphology of the four aggregates were evaluated using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and water absorption measurements as well as SEM observations. Experimental setups were developed to investigate the bonding behavior of the aggregate-mortar interface. The bonding strength between granite and mortar through direct tensile test varied from 51% to 69% of tensile strength of mortar from young age to mature, while 61% to 74% for sandstone, 48% to greater than 90% and 81% to greater than 102% averagely for black and white limestone respectively. The fact of failure in the bulk mortar indicates ITZ adhesion for limestones may equal or exceed the mortar tensile strength generally from 28-day age. This conclusion is consistent with the results obtained by slant shear test. The significant difference of adhesion behavior of ITZ between two limestones due to their water absorption capability. High-water absorption turns out to be beneficial in forming a strong chemical bond at early age, however, the mineralogy remains the pivot under same surface condition. This chemical bond is evidenced by the failure pattern and morphology of the aggregate surface after failure and the presence of a dense accumulation of portlandite and C-S-H under SEM.

Mechanical, environmental, and economic assessment of sustainable cement mortar using Afghan natural pozzolan as a partial replacement for cement

Using natural pozzolan to produce cement-based mortar is one of the suitable solutions to reduce cost, energy consumption, and environmental impacts. In this experimental study, the paste replacement methodology (replacement of partial cement wt% with supplementary cementitious material) is used. Natural pozzolan, as vernacular material with high silicate aluminate originating in Afghanistan, is replaced (6, 13, and 20%) with cement in mortar. Various tests such as slump, compressive strength, tensile strength, water absorption, freezing-thawing cycles, relative length change, pull-off test, and microstructure analysis have been performed to study the properties of fresh and hardened mortar. The findings showed that the use of natural pozzolan containing a high level of silicate and aluminate as a replacement of cement in mortar improved 56 days compressive and tensile strength of mortar by 2.2 and 6%, respectively, water absorption was reduced by 1.6%, and the resistance to the freezing and thawing cycles was increased 10.7% as well compared to the reference samples. In addition, the results of economic analysis and sustainable development indicators assessment of mortar showed that using this replacement methodology was economically acceptable and reduced the potential of global warming and energy consumption by 13% of the production of one ton of cement using standard technology. The optimum replacement percentage was selected at 13% without compromising the mechanical properties of mortar.

Waste-based mortars containing glass powder, GGBS, lead smelter slag and foundry sand reinforced with graphene oxide

The aim of this study is to investigate the possibility of improving the mechanical properties of mortars produced with waste-based binder and sand by incorporating graphene oxide (GO) nanomaterial. Twenty-seven unique mortars were manufactured by replacing cement with glass powder (GP) and ground granulated blast furnace slag (GGBS), and river sand with lead smelter slag and foundry sand. GO was added to mortars at of 0.05% and 0.1% dosages, and flow, compression and tension tests were performed on the mortars. Scanning electron microscopy analyses were carried out to evaluate the mortars' microstructure. The results show that addition of 0.05% GO caused decreased flowability and increased in strength of the waste-based mortar. Increasing GO dosage caused a further decrease in flowability and an increase in compressive and tensile strength of mortars. Strength enhancements in the mortars from 0.05% to 0.1% GO were less significant compared to those from 0% to 0.05% GO. The scanning electron microscopy analyses revealed that mortars reinforced with 0.05% and 0.1% GO exhibited a more compact microstructure with less pores compared to the unreinforced mortars, resulting in improved properties of mortars. The results indicate a significant potential using GO in waste-based mortars for developing a new and sustainable construction material for structural applications.

Research on the back analysis and failure mechanism of recycled concrete aggregate meso-parameters based on Box-Behnken Design response surface model

To obtain the mesophase material parameters of recycled concrete aggregate and analyze the material failure mechanism, based on the Box-Behnken Design, a non-linear material parameter back analysis model of recycled concrete is proposed, and the failure mechanism of recycled concrete materials is explored. Based on the indoor experiment, the numerical simulation experiment of 25 sets of inversion parameters was constructed with the help of Design-Expert. The response surface relationship between different response variables (inversion parameters) and independent variables (mortar elastic modulus, interface elastic modulus, mortar tensile strength, and interface tensile strength) was obtained, which realized the explicit expression of the implicit relationship between mesophase parameters and macroscopic mechanical properties. The mesophase parameters are obtained by inverse analysis, and the stress-strain curve is obtained by bringing it into the numerical model. The comparison with the test results shows that the peak stress error is only 2.8%, the peak strain error is close to 8%, and the fitting degree is good. Combined with the grey relational degree theory, the material failure mechanism is analyzed from the perspectives of the material area ratio of each phase and the mesophase material parameters: the effect of the mortar phase parameters on the stress-strain process is greater than that of the interface phase. The elastic modulus of the mortar has the greatest influence on the stress of each stage, and the tensile strength of the mortar has the greatest influence on the peak strain. This study provides a theoretical basis for the follow-up research on the mechanical properties of recycled concrete.

Numerical Study of Concrete Dynamic Splitting Based on 3D Realistic Aggregate Mesoscopic Model.

In mesoscopic scale, concrete is regarded as a heterogeneous three-phase material composed of mortar, aggregate and interfacial transition zone (ITZ). The effect of mesoscopic structure on the mechanical behaviors of concrete should be paid more attention. The fractal characteristics of aggregate were calculated, then the geometric models of aggregate were reconstructed by using fractal Brownian motion. Based on the random distribution of aggregates, the concrete mesoscopic structure model was established. And the numerical model was generated by using grid mapping technology. The dynamic compression experiments of concrete under Split Hopkinson Pressure Bar (SHPB) loading verify the reliability and validity of the mesoscopic structural model and the parameters of the constitutive model. Based on these, a numerical study of concrete under dynamic splitting is carried out. By changing the parameters of the constitutive model, the effects of tensile strengths of aggregate, mortar and ITZ on the dynamic tensile strength of concrete are discussed. The results show that the dynamic failure of specimen usually occurs at the interfacial transition zone, then extends to the mortar, and the aggregates rarely fail. However, the increase of strain rate intensifies this process. When the strain rate increases from 72.93 s−1 to 186.51 s−1, a large number of aggregate elements are deleted due to reaching the failure threshold. The variation of tensile strengths of each phase component have the same effect on the dynamic tensile strength and energy of concrete. The dynamic tensile strength and energy of concrete are most affected by the tensile strength of mortar, following by the ITZ, but the tensile strength of aggregate has almost no effect.

Experimental and numerical investigations of the tensile behaviour of steel-TRM prepared with recycled glass sands and lime

Due to the decline in the material strength and increase in natural loading, the need to strengthen historical masonry buildings is vital, and different techniques have been used to enhance the structural performance of those buildings. Textile reinforced mortar (TRM) composite systems are one of the newly developed techniques that has attracted increasing interest from researchers. To investigate the feasibility of the use of more eco-friendly materials in mortars, recycled glass sand (RGS) is substituted for natural river sand in the preparation of mortar used in the TRM system, as well as lime as a partial cement replacement. RGS was substituted for river sand at 50% and 100%, and lime was substituted for cement at 50%. A total of ten mix proportions were prepared. The mechanical properties of the mortar were analysed in terms of the flexural strength and compressive strength at 7 and 28 days. The results showed that the strengths tend to decrease as the lime and RGS proportion increases. There are the maximum average reductions of 40.3% in flexural strength and 60.4% in compressive strength for the samples with 50% lime replacement, and 38.3% in flexural strength and 33.8% in compressive strength for the samples with 100% RGS replacement. The discrepancies in the strength increase rate from 7 to 28 days were observed in some samples which may due to the different surface area and grading of RGS particles change the rate of hydration and porous in mortar.Then, the tensile behaviour of steel-TRM prepared with recycled glass sand with four different mix proportions were experimentally studied. The tensile behaviours of the tested coupons agreed well with the three-phase tensile behaviour. The TRM composite coupons prepared with 100% RGS and 50% lime replacement showed the maximum reductions (73.4%) of average tensile strength compare to the TRM coupons with 50% RGS replacement, which follow the trend of the mechanical behaviour of mortar. Finally, analytical and numerical models considering varying parameters related to the material properties were developed to understand the stress–strain responses and crack patterns of different TRM coupons in tension. Both analytical and macromodelling approaches are able to capture the key global tensile behaviour of TRM as a reasonable fitting was observed with regard to predicting the change in the stiffness in the three stages. The results obtained by micromodelling approach show that TRM coupons with 100% RGS show a larger reduction in the mortar tensile strength and bond fracture energy of the mortar-textile interface. The reason for these reductions might be that higher RGS replacement can be more porous in mortar and the angular edges and rough texture of the RGS, respectively.

The hybrid effects of PVA fiber and basalt fiber on mechanical performance of cost effective hybrid cementitious composites

Unlike conventional concrete materials, micromechanical design theory is used in the material design processes of Engineered Cementitious Composites (ECC). The design theory based on micromechanics paves the way for the use of hybrid fibers in order to improve mechanical properties and reduce production costs since the cost of fibers being one of the main components of ECC is high. The combination of fibers up to a certain ratio in the mixtures triggers high tensile ductility (approximately 3% axial tensile strain capacity) along with narrow crack openings. The aim of the study was to improve the basic mechanical properties of hybrid fiber-reinforced cementitious composites by using PVA fiber and basalt fiber as a hybrid in order to decrease production costs. The total fiber content of 2% was formed with three different proportions of basalt fiber and PVA fiber and the impacts on the mortar properties were examined within the scope of the study. First of all, the ECC control sample consisting of only PVA fiber was produced. Then hybrid fibers were added into the mortar in three different combinations as 75% PVA + 25% basalt fiber, 50% PVA + 50% basalt fiber and 25% PVA + 75% basalt fiber at a total fiber content of 2%. Compressive strength, flexural strength, tensile strength and microstructures analyses were made on the mortars and they were compared with the control sample. The optimum hybrid combination was obtained at 75% PVA + 25% basalt fiber. According to the results of the experimental study, approximate results were obtained with respect to the reference sample in flexural strength of mortars and tensile strength of mortars by increasing PVA fiber ratio in the mixtures. As a result, performance characteristics of hybrid fiber reinforced cementitious composites were affected at different levels due to the mechanical and geometrical properties of the fibers used.

Effects of zeolite and silica fume substitution on the microstructure and mechanical properties of mortar at high temperatures

The exposure of concrete to high temperatures leads to mechanical and chemical changes, and the performance of concrete is extremely dependent on its mortar specification. In this study, the compressive and tensile strength of mortar in a temperature range of 28–800 °C is investigated in hot conditions. The microstructure characterization is examined by X-ray diffraction test, thermal gravity analysis, and scanning electronic microscopy test. To minimize the environmental impacts of cement consumption, the possibility of partial replacement of cement with pozzolans is investigated. The results indicate that partial replacement of cement with zeolite and silica fume in the mixing plan of the concrete structure exposed to high-temperature meet both engineering and environmental consideration. Furthermore, the XRD and the TGA results provide valuable information about the prediction of the order of strength and the temperature history of the concrete members. The results pave the way for a better understanding of the high-temperature behavior of pozzolanic mortars.

Multifactorial behavior of the elastic modulus and compressive strength in masonry prisms of hollow concrete blocks

In this paper, a new set of non-linear mathematical expressions to calculate the compressive strength and the elastic modulus of masonry prisms with hollow concrete blocks were obtained. The mathematical models were obtained by multifactorial technique model, which has as advantage: the analysis of the variables associated to the models that provide the main influence on the interaction among the different factors analyzed. It also allows obtaining a nonlinear regression model optimized for each response variable (f’m and Em). Detailed micro-modeling techniques are adopted to simulate the hollow concrete block masonry, describing the experimental tests for the component materials (blocks and mortar) and block-mortar interface. In addition, the structural behavior of the masonry prisms was obtained experimentally. The numerical models were calibrated and validated based on the experimental tests. A sensitivity analysis was carried out by applying a multifactorial complete design 35 and an optimization analysis of the regression models; the compressive strength and the elastic modulus in masonry prisms were evaluated. The results showed that the compressive and tensile strength of the hollow concrete block and the mortar thickness are the most influential parameters for the maximum compressive strength. The compressive strength of the block and the tensile strength of mortar were the most relevant parameters for the elastic modulus in the masonry prisms. In addition, is concluded that, from the analysis and optimization process, both expressions (f’m and Em) are necessarily multifactorial.

Influence of mixing process on mortars rheological behavior through rotational rheometry

Mixing is one of the mortar processing steps (the others being proportioning, transport and application) that, due to its apparent operational simplicity, has been somewhat undermined. However, the mixing process quality has direct influence on the mortar’s rheological behavior and its hardened state properties. In this context, this study’s objective is to assess the influence of two mixing parameters (time and water addition rate) on the characteristics of the produced mortar. Both mixing and flow measurements were performed in a rotational rheometer developed at POLI/USP-Brazil. In this equipment, the mixing strain rate is given as a function of torque evolution. Mortar tensile strength, modulus of elasticity and volumetric porosity were evaluated in its hardened state. “Bad mixing” conditions can arise from too short mixing times or too slow water loading. These bad mixing conditions led to mortars with lower mechanical strength and more unfavorable rheology, meaning high thixotropy and flow curve loops with big hysteretic area. When admixture was employed, mixing resulted in a mortar with higher entrained air leading to negative effects on the mechanical properties of the hardened material.

Effect of Graphene Oxide Nanosheets dispersion in cement mortar composites incorporating Metakaolin and Silica Fume

In this work, the reinforcing effects of Graphene Oxide Nanosheets dispersions (GOD) on high strength cement mortar are investigated, evaluating possible improvements in mechanical properties, fluidity, Sorptivity and water absorption resistance. Mortar with water/cement ratio of 0.5, GOD dosage varying from 0 to 0.20% by weight of cement and sand at a proportion of 3× weight of the cement were prepared, in addition to 10% and 20% replacement/no replacement with Silica Fume and Metakaolin respectively to improve the GO nanosheets dispersion. The GO used in the matrix forms aggregate due to presence of divalent Calcium ions. Hence to split the particles vigorous mixing was done. The results indicate that the addition of GOD accelerate the cement hydration reactions, increase the compressive strength and tensile strength of the mortar, reduce the pore volume and harden cement properties. However, the fluidity decreased with increasing GOD content. The optimal compressive strength was achieved with samples designed with GOD dosage of 0.05% with replacement, for which the corresponding increases were 72.41%, 84.61% and 90.90%, after 3,7 and 28 days respectively, compared with samples without GOD and replacement. The tensile strength of the cement mortar increased with GOD content to 132%, 178.6% and 181.2% for 3, 7 and 28 days respectively with replacement and GOD dosage of 0.10%. Furthermore, FE-SEM observation indicated that the GOD probably had an effect on the shape of the cement hydration products. It revealed samples containing 0.10 wt% GOD with replacement exhibited good bonding between the GOD and the surrounding cement matrix. The hydration mechanism of cement composites with GOD and replacement of cement with Silica Fume and Metakaolin needs further study.

Strength of mortar containing rubber tire particle

The main focus in this investigation is to determine the strength consist compressive and tensile strength of mortar containing rubber tire particle. In fact, from the previous study, the strength of mortar containing waste rubber tire in mortar has a slightly decreases compare to normal mortar. In this study, rubber tire particle was replacing on volume of fine aggregate with 6%. 9% and 12%. The sample were indicated M0 (0%), M6 (6%), M9 (9%) and M12 (12%). In this study, two different size of sample used with cube 100mm x 100mm x 100mm for compressive strength and 40mm x 40mm x 160mm for flexural strength. Morphology test was conducted by using Scanning electron microscopic (SEM) were done after testing compressive strength test. The concrete sample were cured for day 3, 7 and 28 before testing. Results compressive strength and flexural strength of rubber mortar shown improved compare to normal mortar.

ENGINEERING PROPERTIES OF HIGH VOLUME BIOMASS WASTE MORTAR

This paper represents the effects of using waste generated from palm oil industries like ash, shell and fibre on the engineering properties of mortar. Palm Oil Fuel Ash (POFA) was used as cement replacement up to 60% and Oil Palm Kernel Shell (OPKS) as sand replacement in mortar mixture. The Oil Palm Fibre was added to increase the strengthening performance of mortar. The method used to find the water binder ratio was by trial and error method with 1:3 ratio of cement to sand. The cubes size of 70mm x 70mm x 70mm, beams size of 40mm x 40mm x 160mm, and cylinders size of 70mm diameter and 150mm height, were cast and tested for compressive strength, flexural strength and splitting tensile strengths of mortar. Samples were cured in water before testing it at 7, 28, and 60 days. Also, the water absorption of mortar was tested at the age of 28 days. The results showed that oil palm fibre provided more advantages and increase the strength properties especially in the flexural and tensile strength. The addition of Oil Palm Kernel Shell reduced the density of mortar and it can be used for lightweight application. The test results also showed that as the POFA ratio increased, the compressive strength of mortar decreased. However, as OPKS ratio increased, the density was found to be decreased. The mix proportions using 60% POFA and 20% OPKS was considered as the optimum mix design. The mortar showed optimum strength at 9% with the addition of fibre.

EFFECT OF CERAMIC AGGREGATE ON HIGH STRENGTH MULTI BLENDED ASH GEOPOLYMER MORTAR

Geopolymer is a type of amorphous alumino-silicate cementitious material, synthesized by the reaction of an alumina-silicate powder with an alkaline solution. The geopolymer technology has recently attracted increasing attention as a viable solution to reuse and recycle industrial solid wastes and by-products. This paper discusses the performance of geopolymer mortar comprises of multiple blended ash of palm oil fuel ash (POFA), pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBFS) by replacing ordinary Portland cement. Fine aggregate obtained from the ceramic waste was used to partially replace normal sand in the mixture. The concentration of alkaline solution used was 14 Molar. The fresh mortar was cast in 50x50x50 mm cubes geopolymer mortar specimens and cured at ambient temperature for 24 hours. The effects of mass ratios of alkaline solution to multiple blended ashes and percentage of ceramic aggregate as sand replacement on compressive, flexural and tensile strength of mortar were examined. The results revealed that as the multi blended ash (GGBFS: PFA: POFA) mass ratio increased, the compressive strength of geopolymer mortar is increased with regards to the ceramic aggregate properties.

Determination of mortar strength using stone dust as a partially replaced material for cement and sand

Mortar is a masonry product which is matrix of concrete. It consists of binder and fine aggregate and moreover, it is an essential associate in any reinforced structural construction. The strength of mortar is a special concern to the engineer because mortar is responsible to give protection in the outer part of the structure as well as at a brick joint in masonry wall system. The purpose of this research is to investigate the compressive strength and tensile strength of mortar, which are important mechanical properties, by replacing the cement and sand by stone dust. Moreover, to minimize the increasing demand of cement and sand, checking of appropriateness of stone dust as a construction material is necessary to ensure both solid waste minimization and recovery by exchanging stone dust with cement and sand. Stone dust passing by No. 200 sieve, is used as cement replacing material and retained by No. 100 sieve is used for sand replacement. Sand was replaced by stone dust of 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% by weight of sand while cement was replaced by stone dust of 3%, 5%, and 7% by weight of cement. Test result indicates that, compressive strength of specimen mix with 35% of sand replacing stone dust and 3% of cement replacing stone dust increases 21.33% and 22.76% respectively than the normal mortar specimen at 7 and 28 days while for tensile it increases up to 13.47%. At the end, optimum dose was selected and crack analysis as well as discussion also included.

Determination of mortar strength using stone dust as a partially replaced material for cement and sand

Mortar is a masonry product which is matrix of concrete. It consists of binder and fine aggregate and moreover, it is an essential associate in any reinforced structural construction. The strength of mortar is a special concern to the engineer because mortar is responsible to give protection in the outer part of the structure as well as at a brick joint in masonry wall system. The purpose of this research is to investigate the compressive strength and tensile strength of mortar, which are important mechanical properties, by replacing the cement and sand by stone dust. Moreover, to minimize the increasing demand of cement and sand, checking of appropriateness of stone dust as a construction material is necessary to ensure both solid waste minimization and recovery by exchanging stone dust with cement and sand. Stone dust passing by No. 200 sieve, is used as cement replacing material and retained by No. 100 sieve is used for sand replacement. Sand was replaced by stone dust of 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% by weight of sand while cement was replaced by stone dust of 3%, 5%, and 7% by weight of cement. Test result indicates that, compressive strength of specimen mix with 35% of sand replacing stone dust and 3% of cement replacing stone dust increases 21.33% and 22.76% respectively than the normal mortar specimen at 7 and 28 days while for tensile it increases up to 13.47%. At the end, optimum dose was selected and crack analysis as well as discussion also included.

Efficiency of Discrete Glass Fiber Reinforced Cement Mortar in Compression

The cement mortar with glass fiber (GF) can be widely used in strengthen different structure elements. In general, discrete glass fiber was used for improving the tensile strength of mortar. In article, the optimum material contents (sand, cement, water and fiber) enhancement compression strength with tensile strength was investigated. Forty-two specimens are tested after 28 days. Each specimen has of 3 cubes 15*15*15 and the average results were taken into consideration. The mortar content is cement, sand, water and discrete glass fiber. The fiber lengths (L f) are 20, 35, 50 mm. the fiber contents ( Vf ) are 1.5%, 3.0% and 4.5%. The water cement ratios (W/C) are 0.47, 0.42, and 0.37. The cement sand ratios (C/S) are 1:2, 1:3 and 1:4. The results show that, b y reducing the C/S ratio, the discrete glass fiber used is not recommended using. Moreover, from the experimental studies, the curves required for awareness the mixed material of mortar with discrete glass fiber were plotted. The theoretical equation that can be used in the initial trial mixing design is determined. This type of mortar can be successfully used for repairing or strengthen brick wall, or replaced instant of steel mish for resistance change temperature between wall layers.

Sustainable masonry mortar for brick joint and plaster in the UK

Blended mixtures of ground granulated blastfurnace slag and Portland cement were used in making sustainable masonry mortars suitable for brick joints and for plastering, with Portland cement mortar as control. The testing programme included the determination of a relationship between the mortar flow value and mortar water demand for a wide range of mix compositions. The mortar tensile strength is not a very critical property due to the fact that brickwork mortar is not usually under tension when in service; however, this parameter was determined in the laboratory using a standard briquet towing/testing machine. Chemical durability of the control and blended mortar in aggressive sulfate-bearing exposure conditions was investigated. The relationship between compressive strength of the mortar cured in water and in sodium sulfate solution at room temperature (20 ± 2°C) for from 3 to 120 days was established. The results demonstrated that after a prolonged period of exposure, significant strength and weight loss in the control mortar was observed. This phenomenon is explained, due to calcium hydroxide production as a consequence of Portland cement hydration, change in mortar morphology, inhibition of reaction species and the final disruption of the mortar matrix, resulting in loss of strength and weight at late age. The results obtained suggest that ground granulated blastfurnace slag can be incorporated into Portland cement for the development of sustainable and durable mortars in the UK.