Cement Mortar Mixtures Research Articles

Influence of rheological properties of cement mortar on steel fiber distribution in UHPC

This paper aims to study the distribution of steel fibers in UHPC specimens prepared by different rheological cement mortar. Four levels of superplasticizer dosage were used for every water to binder ratio (0.18, 0.20, 0.22, 0.24) to adjust rheological properties of cement mortar mixtures (without steel fibers). Steel fibers were added by volume of 1%, 2% and 3% for every cement mortar mixture respectively. Cube specimens (70.7×70.7×70.7mm3) were cast and cured under the same condition for every mixture and the distribution of steel fibers along casting depth was determined by digital image processing. The experimental results reveal that the flowability of fresh cement mortar increases and the yield stress decreases with the higher water to binder ratio and superplasticizer dosage. The plastic viscosity of fresh mixture is decreased by the higher water to binder ratio and little influenced by the variation of superplasticizer dosage. The fiber distribution along depth mainly depends on rheological parameters of fresh mixture, especially the yield stress. Moderate rheological parameters are necessary for obtaining an uniform distribution of steel fibers in UHPC. On the basis of this study, the optimal yield stress of fresh matrix ranges among 900–1000Pa, 700–900Pa and 400–800Pa respectively for UHPC mixtures with 1%, 2% and 3% fiber volume fraction.

Prediction of compressive strength of lightweight mortar exposed to sulfate attack

This paper summarizes the results of experimental research, and artificial intelligence methods focused on determination of compressive strength of lightweight cement mortar with silica fume and fly ash after sulfate attack. The artificial neural network and the support vector machine were selected as artificial intelligence methods. Lightweight cement mortar mixtures containing silica fume and fly ash were prepared in this study. After specimens were cured in 20+-2oC waters for 28 days, the specimens were cured in different sulfate concentrations (0%, 1% MgSO-2 4, 2% MgSO-2 4, and 4% MgSO-2 4) for 28, 60, 90, 120, 150, 180, 210 and 365 days. At the end of these curing periods, the compressive strengths of lightweight cement mortars were tested. The input variables for the artificial neural network and the support vector machine were selected as the amount of cement, the amount of fly ash, the amount of silica fumes, the amount of aggregates, the sulfate percentage, and the curing time. The compressive strength of the lightweight cement mortar was the output variable. The model results were compared with the experimental results. The best prediction results were obtained from the artificial neural network model with the Powell-Beale conjugate gradient backpropagation training algorithm.

The transformation of waste Bakelite to replace natural fine aggregate in cement mortar

Bakelite material has been used to produce the various components for cars and consumer goods industry in Thailand. The growth of Bakelite consumption increases Bakelite waste. Bakelite waste is prohibited from disposing of direct landfilling and open burning because of the improper disposal and emission reasons. A large amount of this waste needs the large safe space of warehouse area for keeping which becomes a waste management problem. Size reduction by milling machine is helpful for waste handling and storing, however, the post-milling waste Bakelite plastic utilization shall be studied to maintain the waste storing capacity. There are some studies of the milling machine used for waste plastic size reduction. However, the particular study of milling machine application for waste size reduction and its milling waste utilization is still insufficient in Thailand. The purpose of this research is the use of waste Bakelite aggregate milling machine for Bakelite waste size reduction and use of the post-milling waste Bakelite as a fine aggregate to replace natural sand material in cement mortar. The waste Bakelite fine aggregate (WBFA) was mixed in cement mortar mixture with the proportion 0% 20% 40% 60% 80% and 100% by volume for cement mortar sample preparation. The mortar sample was tested for compressive strength follow ASTM standard. The compressive test result of mortar samples will be compared between conventional mortar (0% WBFA) and waste Bakelite mortar (WBM) as well as comparing with the mortar standard. From an analysis of the sample test data found that the WBFA content in cement mortar mixture can predict the strength of WBM. The compressive strength of WBM at 28days age with the fraction of WBFA is not exceeded 11.03%, and 23.08% respectively can be met the mortar standard according to the equation. The utilization of WBM to develop mortar non-structural mortar product can be usable from a technical point of view.

Fractal analysis of relation between strength and pore structure of hardened mortar

The pore structure is the fatal factor which influences the strength of cement mortar and concrete. A lot of researches on the relationship between the strength and the pore structure were developed. Initially, porosity is the only factor in the strength models. As the development of research, it is illustrated that the pore size distribution also has significant effect on the strength. The pore size distribution is taken into consideration in the strength model in different forms. However, these models are still unavailable to simulate the relationship between strength and pore structure, because the parameters used for representing the pore size distribution are not accurate enough. In the present research, strength and pore structure were tested on thirteen Portland cement mortar mixtures to collect the original data of the strength and pore structure. In order to enhance the reliability of the strength model, the pore volume and the pore size distribution were all considered. The fractal theory was employed to characterize the pore size distribution more accurately than ever used parameters. According to the regression analysis results, the fractal dimension of pore surface and the capillary pore volume were respectively selected as representative parameters of pore size distribution and pore volume. The research results indicate that the relations between strength and fractal dimension and capillary pore volume present positive power function and negative power function respectively. The ratio of fractal dimension to capillary pore volume is addressed as the new parameter for strength model. Finally, relational expression of power function is proposed between the compressive strength and the ratio of fractal dimension to capillary pore volume. Regression analysis indicates that the strength model relative to pore structure addressed in this study has high prediction accuracy.

Compressive Strength and High-Temperature Residual Strength of Cement Specimens Containing Bagasse Ash

Cement is currently the most versatile and widely used material in construction. However, the high carbon emissions and energy consumption associated with the manufacture of cement remains a serious concern. bagasse ash (BA) is a secondary waste product of bagasse-fired power generation. This study investigated the use of BA as a replacement for cement as a means of reducing the environmental impact of concrete-based construction. At 28 days, we measured the water absorption of cement mortar specimens as well as the compressive strength at room-temperature and after heating. Experiments were conducted involving the replacement of various proportions of cement using BA and fly ash (FA), followed by a comparison of the physical properties. Our test results demonstrate the applicability of BA in the production of cement mortar mixtures with high water-binder ratios. It was found that the water-binder ratio determines the optimal proportion of BA when used as a replacement for cement, wherein a higher water-binder ratio means that more of the cement can be replaced with BA. In compressive strength respect, the optimal cement replacement with BA was 15 % to 25 %, whereas the optimal cement replacement with FA was 20 %. BA was shown to have a more pronounced effect in reducing water absorption in cement mortar specimens with high water-binder ratios (0.55 to 0.65). The compactness of specimens with lower water absorption enables them to retain more of their initial compressive strength following exposure to high temperatures.

Mechanical and radiation shielding properties of mortars with additive fine aggregate mine waste

Incorporation of barite-fluorspar mine waste (BFMW) as a fine aggregate additive has been investigated for its effect on the mechanical and shielding properties of cement mortar. Several mortar mixtures were prepared with different proportions of BFMW ranging from 0% to 30% as fine aggregate replacement. Cement mortar mixtures were evaluated for density, compressive and tensile strengths, and gamma ray radiation shielding. The results revealed that the mortar mixes containing 25% BFMW reaches the highest compressive strength values, which exceeded 50MPa. Evaluation of gamma-ray attenuation was both measured by experimental tests and computationally calculated using MicroShield software package, and results have shown that using BFMW aggregates increases attenuation coefficient by about 20%. These findings have demonstrated that the mine waste can be suitably used as partial replacement aggregate to improve radiation shielding as well as to reduce the mortar and concrete costs.

Effect of gypsum type on properties of cementitious materials containing high range water reducing admixture

In this study, the effect of cement gypsum type on properties of the properties of cement paste, mortar and concrete mixtures containing high range water reducing admixture (HRWR) was investigated. Two different types of cement prepared from the same clinker but containing either calcium sulfate hemihydrate or dihydrate as retarder were used. The fresh and hardened (compressive strength and drying-shrinkage) properties as well as static and dynamic rheological behavior of the mixtures were investigated. Compared to the mixtures containing dihydtate, the fresh and rheological properties of mixtures were negatively affected when cement-containing hemihydrate was used. However, hemihydrate utilization had a positive influence on the early compressive strength. The adverse effects on fresh properties were more significant in paste mixtures. These negative effects decreased in the mortar and concrete mixtures. The presence of hemihydrate in cement was found to increase the drying-shrinkage.

Residual Strength of Blended Cement Pastes and Mortar Exposed to Elevated Temperatures

This paper presents the outcome of a series of tests to determine properties of blended cement pastes and mortar mixtures using Taguchi’s design of experiment approach. Fly ash (FA), water to cementitious material ratio (w/c), superplasticiser (SP) and sand to cementitious material ratio (s/c) are the main parameters considered. Mixture samples were tested at varying temperatures up to 800oC. The ANOVA results and regression analysis show that an increase in FA content and w/c ratio lead to a decrease in the density of blended cement. For compressive strength development, an increase in FA content and s/c ratio decreased the compressive strength development. Within the tested levels of the parameters, the optimum mix to achieve the highest compressive strength of blended cement mixtures is 20% of FA content, 1.5 of s/c ratio, 0.35 of w/c ratio and 0.2% of SP. Increasing the content of FA and SP improved the overall residual strength, and the optimum mix design to achieve the highest residual strength is 20% of FA, 1.5 of s/c ratio, 0.35 of w/c ratio and 0.2 of SP. Based on all the test results, an empirical formula for predicting residual strength of blended cement paste and mortar is proposed.

An experimental study on thermal conductivity of iron ore sand cement mortar

The objective of this paper is to determine the effect of water–cement ratio, total sand–cement ratio, river sand–iron ore sand ratio, temperature and density on the thermal conductivity of iron ore sand (IOS) cement mortar. The IOS was filtered by wet magnetic separator and incorporated in a cement mortar mixture. The hot-wire method and the laser flash method were used to test the thermal conductivity of the IOS cement mortar. Meanwhile, the SPSS partial correlation analysis was conducted to determine the precedence of the five factors according to their effects on thermal conductivity. After that, a prediction formulation of thermal conductivity was developed with MATLAB. Experimental results show that among the five factors, river sand–iron ore sand ratio ranks the best effect on thermal conductivity, followed by water–cement ratio, total sand–cement ratio, temperature and density in sequence.

Effects of silica additives on fracture properties of carbon nanotube and carbon fiber reinforced Portland cement mortar

Fiber reinforcements provide many benefits to cementitious composites, including reduction of crack widths and increases in ductility. However, the interfacial transition zone between fibers and hydrated cement can contain a high proportion of calcium hydroxide and porosity. With their high moduli of elasticity, carbon nanotubes and carbon fibers could provide substantial mechanical reinforcement at multiple length scales, but only if their bond to the matrix can be controlled. Surface treatments of fibers and addition of supplemental materials in the matrix can influence both the mechanical interaction at the interface and the dispersion of these relatively small reinforcements. We performed a broad study of Portland cement mortar mixtures containing silica fume, plain or silica-functionalized carbon nanotubes, and carbon fibers to characterize changes in fracture properties. The early age hydration kinetics of cement pastes containing carbon nanotubes were compared using isothermal calorimetry. Early age fracture surfaces of cement pastes containing carbon fibers were observed using a scanning electron microscope. The notched beam test method of the Two Parameter Fracture Model was used to determine the fracture properties of each mix. We observed that silica fume and silica functional groups improved the fracture performance of mixtures containing carbon nanotubes and carbon fibers. Further optimization of dosage, size, and interface strength is required to fully utilize carbon nanotubes in cementitious composites.

Studies on use of Copper Slag as Replacement Material for River Sand in Building Constructions

This work focuses on the use of copper slag, as a partial replacement of sand for use in cement concrete and building construction. Cement mortar mixtures prepared with fine aggregate made up of different proportions of copper slag and sand were tested for use as masonry mortars and plastering. Three masonry wall panels of dimensions 1 × 1 m were plastered. The studies showed that although copper slag based mortar is suitable for plastering, with the increase in copper slag content, the wastage due to material rebounding from the plastered surfaces increases. It is therefore suggested that the copper slag can be used for plastering of floorings and horizontal up to 50 % by mass of the fine aggregate, and for vertical surfaces, such as, brick/block walls it can be used up to 25 %. In this study on concrete mixtures were prepared with two water cement ratios and different proportions of copper slag ranging from 0 % (for the control mix) to 100 % of fine aggregate. The Concrete mixes were evaluated for workability, density, and compressive strength.

Correlation Between Destructive And None-Destructive Tests on the Mechanical Properties of Different Cement Mortar Mixtures Incorporated Polyethylene Terephthalate Fibers.

Non-destructive tests have been widely used in engineering purposes especially in civil engineering. Yet it is not properly used to predict the mechanical properties of different cement mortar mixtures reinforced with plastic fibers (PET) made from waste plastic bottles. In this study, the pulse velocity was used to predict the mechanical properties of cement mortar mixtures reinforced with and without plastic fibers made from waste plastic fibers. The Pulse velocity was computed from samples of different cement mortar mixtures with different ratio of cement/sand. Then the desired mechanical properties of mortar samples were calculated from the laboratory tests. Then, the Pulse velocity results were correlated with the destructive test results using simple regression analysis. The results showed that the mechanical properties (Uniaxial Compressive Strength, Modulus of Elasticity, and Tensile strength) can be predicted from the correlation equations proposed in this study.

Chemical, Mechanical, and Durability Properties of Concrete with Local Mineral Admixtures under Sulfate Environment in Northwest China.

Over the vast Northwest China, arid desert contains high concentrations of sulfate, chloride, and other chemicals in the ground water, which poses serious challenges to infrastructure construction that routinely utilizes portland cement concrete. Rapid industrialization in the region has been generating huge amounts of mineral admixtures, such as fly ash and slags from energy and metallurgical industries. These industrial by-products would turn into waste materials if not utilized in time. The present study evaluated the suitability of utilizing local mineral admixtures in significant quantities for producing quality concrete mixtures that can withstand the harsh chemical environment without compromising the essential mechanical properties. Comprehensive chemical, mechanical, and durability tests were conducted in the laboratory to characterize the properties of the local cementitious mineral admixtures, cement mortar and portland cement concrete mixtures containing these admixtures. The results from this study indicated that the sulfate resistance of concrete was effectively improved by adding local class F fly ash and slag, or by applying sulfate resistance cement to the mixtures. It is noteworthy that concrete containing local mineral admixtures exhibited much lower permeability (in terms of chloride ion penetration) than ordinary portland cement concrete while retaining the same mechanical properties; whereas concrete mixtures made with sulfate resistance cement had significantly reduced strength and much increased chloride penetration comparing to the other mixtures. Hence, the use of local mineral admixtures in Northwest China in concrete mixtures would be beneficial to the performance of concrete, as well as to the protection of environment.

Flow characteristics of ternary blended self-consolidating cement mortars incorporating palm oil fuel ash and pulverised burnt clay

This article aims at investigating the flow characteristics of self-consolidating cement mortars incorporating palm oil fuel ash (POFA) and pulverised burnt clay (PBC). These mortars were tested with respect to their flow spread. Fifteen (15) different cement mortar mixtures were prepared containing Ordinary Portland Cement (OPC) and a blend of POFA and PBC at 0%/0%, 5%/5%, 10%/5%, 10%/10% and 15%/15% as a replacement of OPC. Water-to-binder ratio (W/B) of 0.3, 0.35 and 0.4 were used in all the mortar mixtures. The flow spreads of the mortars were determined using a standard flow mould and subsequently the relative flow areas were measured. The effects of different W/B, high range water reducer (HRWR) dosage and the blend percentage of POFA and PBC on flow characteristics of the various mortars were analysed and reported. Results showed that the flow of the mortar increased with the increase in POFA/PBC content and HRWR dosage while it decreased at higher W/B. Nonetheless, higher dosage of HRWR resulted in the bleeding of mortar. This study also showed that blended POFA/PBC can be used up to 30% replacement with a maximum HRWR content of 2.5% to design and produce self-consolidating cement mortar and concrete.

Oil Palm Shell Ash: Cement Mortar Mixture and Modification of Mechanical Properties

The waste agriculture materials cause environment pollution, recycle of these materials help sustainable development. This study focused on the impact of used oil palm shell ash on the compressive and flexural strengths of cement mortar. Two different cement mortar mixes have been designed to investigate the impact of oil palm shell ash on strengths of cement mortar. Quantity of 4% oil palm shell ash has been replaced in cement mortar. The main objective of this paper is, to modify mechanical properties of cement mortar by replacement of oil palm ash in it at early age of 7 days. The results have been revealed optimum quantity of oil palm ash for replacement in cement mortar. The deflection, load to failure, time to failure of compressive strength and flexural strength of all specimens have significantly been improved. The stress-strain behavior has been indicated ability of modified cement mortar in control stress path and strain. The micro property of cement paste has not been investigated.

Properties of Alkli-Activated Slag Cement Compounded with Soluble Glasses with a High Silicate Modulus

Properties of alkali-activated slag cements compounded with soluble glasse with a high silicate modulus Ms=2.6 were detailedly studied in this paper, including compressive strength and flexure strength characterictics at the ages of 3,7,28 days and flow values of fresh cement mixtures on a jolting table. As a result, with the compressive strength at the age of 28 days of 95.6-107.8 MPa has been developed, and the flow values and strength characteristics of alkali-activated slag cement mortars increased with increase in a water to cement (alkaline activator solution to slag) ratio, and the flow value (determined on the cement mortar mixtures) would reach 145 mm. Moreover, the development speed of strength characteristics of mortar specimens would be affected negatively by increasing of water demand (requirement).

Influence of sugar-cane bagasse ash and fly ash on the rheological behavior of cement pastes and mortars

In the present study, the effects of a sieved sugar cane bagasse ash (SCBA) and fly ash (FA) on the rheological properties of pastes and mortars were investigated. Cement pastes and mortar mixtures were designed as single ingredient, binary and ternary systems. For the single ingredient system only cement was used. For the binary system, SCBA or FA was used to replace some of the cement. For the ternary systems, combinations of cement, SCBA and FA were used. The rheological tests were carried out with a stress controlled rheometer equipped with a ball measuring system. In addition, mini-slump cone and the flow/spread table tests were carried out to determine the feasibility of evaluating the rheological properties of pastes and mortars from empirical tests. The results indicate that for the binary pastes and mortars, there is an inverse relationship between the yield stress and FA concentration. On the other hand, the shape and size of the particles of the used SCBA produced more viscous and plastic binary pastes and mortars than mixes without the SCBA. When the SCBA concentration was increased, the yield stress linearly increased as well. In the ternary systems, the use of 20% of FA combined with 10% and 20% of SCBA was beneficial producing lower yield stresses than those presented in the binary system. The results obtained with the mini-slump cone and the flow/spread table tests showed a certain relationship with the rheological measurements, but this could not be completely identified.

Properties of cement mortar incorporating de-inking waste-water from waste paper recycling

This paper presents results of an investigation into the potential use of recycling paper mill waste-water to replace mixing water in cement mortar systems for manufacturing concrete masonry products. The physical and mechanical properties of mortar containing various amounts of de-inking waste-water were consequently investigated. A key finding of this study was that replacing mortar mixing water with waste-water significantly improved workability and consistency of cement mortar mixtures. In particular the flow of mortar mixtures increased with increase of waste-water content up to 50% and then levelled off when waste-water content exceeded 50%. Correspondingly, the flow of mortar mix with 100% waste-water replacement at water/cement ratio of 0.50 was found to be equivalent to that of the reference mortar mix with 100% potable water at water/cement ratio of 0.60, indicating potential use of de-inking waste-water as water reducing admixture. The enhanced workability arising from waste-water addition however induced changes in mechanical properties of the hardened material. Compared to reference mortar, replacing 10% and 100% potable water respectively resulted in 19% and 60% reduction of compressive strength, with a corresponding 5% and 16% drop in bulk density, and up to 19% increase in drying shrinkage. Also, water absorption and volume of permeable voids increased with increasing waste-water dosage, albeit marginally. The benefits derived from rheology improvements compared to compromises in mechanical properties due to de-inking waste-water addition strongly indicate clear potential of using de-inking waste-water in production of lightweight cementitious building and masonry elements.

Feasibility of using recycled glass in architectural cement mortars

► It is feasible to produce aesthetically-pleasing architectural mortar by using 100% recycled glass as decorative aggregate. ► It is possible to use self-compacting based approach to produce architectural mortar. ► Use of recycled glass has improved the fluidity, drying shrinkage , and resistance to acid attack. ► The flexural and compressive strength decreased with the increase in glass content. ► Metakaolin is found to be an effective suppressor to mitigate the ASR expansion of glass mortar. The feasibility of using 100% recycled glass (RG) as a fine aggregate replacement in architectural white cement mortar was investigated. All the cement mortar mixtures were proportioned with a fixed water to binder ratio of 0.40. The dosage of superplasticizer was varied to produce highly workable recycled glass self-compacting white cement mortar (RG-SCWM) mixtures. Metakaolin (MK) was used in the RG-SCWM mixtures to suppress alkali-silica reaction (ASR). The test results revealed that increased in the recycled glass (RG) content improved the performance of workability and drying shrinkage. However, there was a gradual reduction in flexural and compressive strengths as the content of RG increased. The incorporation of MK effectively mitigated the ASR expansion and also increasing the resistance towards acid attack. Overall results have proved that it is feasible to produce aesthetically-pleasing architectural cement mortar by using 100% recycled glass as the fine aggregate.

Utilization of separator bag filter dust for high early strength cement production

This paper presents the feasibility of incorporating ultra-fine particles collected in the separator bag filter during the process of manufacturing cement (SBFC) as an substitution material for cement. Approximately 2.5% of SBFC is produced during OPC manufacturing process. Also, the average size of SBFC particles is about 5 μm, the average size of OPC particles is about 14 μm. This method does not require additional processes needed in the existing processes to manufacture high early strength cement such as modifying mineral components and adjusting the firing temperature. Moreover, it can also solve the issue of efficiency decrease resulted from the increase of the grinding time applied in the existing process of manufacturing microcement. In order to investigate the characteristic properties of this cement mixture, cement blends have been produced by using different amounts of SBFC. While the blaine value of 100% SBFC was significantly higher (6953 cm 2/g) than that of Ordinary Portland Cement (OPC), its chemical composition showed no significant difference. Cement paste, mortar mixtures have been prepared by using cement blends incorporating 0, 50 and 100% SBFC by weight. Flowability, setting time and compressive strength tests has been performed. Test results showed that substitution of SBFC negatively affect the flowability of cement paste and mortar mixtures. Moreover, setting times shortened, compressive and flexural strength values increased by the substitution of SBFC. Finally, microstructure analysis of cement paste samples showed that incorporation of SBFC reduced the internal porosity by 9% as determined by the proposed method. The internal porosity of paste was measured by mercury intrusion porosimetry (MIP). The compressive strength and bending strength of mortar were higher in the order of 100, 50 and 0% SBFC mixed.