Behavior Of Mortar Research Articles

Strength, carbon emissions, and sorptivity behavior of cement paste and mortar containing thermally activated clay

The detrimental impact of anthropogenic gases such as carbon dioxide, methane, and nitrous oxide has become a pressing concern across various industries. In this study, thermally activated clay (TAC) was investigated as a substitute for Portland cement in proportions ranging from 10 to 40 wt%. Compressive strength and efficiency factors were employed to ascertain the optimal mortar mixture. Both the control mortar and the optimal blend underwent capillary water sorptivity tests. Fourier Transformed Infrared spectroscopy (FT-IR) was utilized to gain insight into the hydration process and pozzolanic reaction within the mortar mixtures. Furthermore, the study assessed the impact of the optimized blended mortar on greenhouse gas emissions through estimated carbon dioxide equivalent values. Results revealed that incorporating 30% TAC attained the maximum strength of approximately 33, 36, and 48 MPa at 3, 7, and 28 days respectively compared with the other mortars. The mortar containing 30% TAC enhances both compressive strength and efficiency factors, demonstrating effective pozzolanic activity and minimal compromise on performance. Notably, the inclusion of 30% TAC also led to reduced water absorption rates, indicating improved durability-related performance. Additionally, the study uncovered the superior performance of the 30% TAC mix in terms of efficiency factors and carbon savings. FTIR analysis provided novel insights into the hydration and pozzolanic reactions induced by TAC, resulting in the formation of compounds contributing to enhanced compressive strength over time. This research advocates for the substitution of Portland cement with TAC as a low-carbon binder alternative to traditional Portland cement binders.

Synergistic effects of different ionic surfactants and temperature on rheological behavior and air-void structure of cement mortar

The influence of air entrainment on rheological behavior of fresh cementitious materials has attracted a lot of attention in the past years, but the results are still in controversy. In this research, cement mortars were prepared with equivalent air contents using different air-entraining admixtures (AEAs) to measure their fresh-state performance and hardened air-void system at variable temperature conditions, which aimed to clarify and unveil the coupled effects of different surfactants and temperature for the first time. The adsorption amount of AEA, zeta potential of cement, along with hydration kinetics of mixtures were evaluated to characterize the interaction of air bubbles with cement grains. It was found that for mixture without superplasticizer (SP), the impact of air entrainment on rheological parameters was dependent on the interaction intensity of AEA molecules with cement. For SP-plasticized mixture, air entrainment tended to cause a shear-thinning behavior with decreased plastic viscosity, while its influence on yield stress was in accordance with the situation without SP. The hardened samples with anionic surfactant contained more small voids and lacked big voids, whereas the samples with cationic surfactant showed opposite outcomes. With temperature decreasing, both the average chord length and the spacing factor of air voids increased owing to the reduced yield stress of mixture. The results will provide in-depth illustrations for understanding how air bubbles change the rheological behavior of mixture, and more importantly it will explain the seemingly inconsistent findings reported by previous literatures.

Two scale models for fracture behaviours of cementitious materials subjected to static and cyclic loadings

This study employs a lattice fracture model to simulate static and fatigue fracture behaviour of Interfacial Transition Zone (ITZ) at microscale and mortar at mesoscale. The heterogeneous microstructure of ITZ and mesostructure of mortar are explicitly considered in the models. The initial step involves calibrating and validating the microscopic model of the ITZ through micro-cantilever bending tests. Subsequently, this validated ITZ model serves as a constitutive law to simulate the fracture behavior of mortar at the mesoscale using an uncoupled upscaling method. The influence of microstructural features, such as w/c ratio and microscopic roughness, on the fracture behaviour of ITZ is investigated. Moreover, the effect of ITZ properties and stress level on the fracture performance and fatigue damage evolution of mortar is also studied. The simulation results for both the ITZ and mortar demonstrate good agreement with experimental results. The proposed two models provide insights into the fracture mechanisms and fatigue damage evolution in cementitious materials subjected to static and cyclic loadings.

Behavior of earth mortars at high temperature

This study investigates the behavior of different earth mortar compositions when exposed to elevated temperatures, considering factors such as the mineralogical nature and volumetric fraction of the aggregates used. Earth mortars made from a combination of a silty-clay earth, silica-calcareous sand and fired red ceramic bricks waste were investigated. Density, thermal conductivity, ultrasonic wave velocity, flexural and compressive strength are determined at 200°C, 400°C, 600°C and 600°C. Results show that incorporating aggregates reduces linear shrinkage and bulk density. The use of fired brick waste reduces the density, thermal conductivity and ultrasonic wave velocity. As the temperature increases up to 600°C, thermophysical properties of the mortars decrease but their compressive strength increases. At the temperature of 800°C, the mortars with silica-calcareous aggregate show a significant degradation but the addition of fired brick waste reduces the damage. TG/DSC analysis and SEM observations provided a better understanding of the reactions. The results obtained can be used to optimize the performance of earth mortars at elevated temperatures.

The impact of supplementary cementitious materials on the rheological and mechanical properties of mortars based on quarry waste sand

Mineral substances used as additives in cement plants or as additives in the making of concrete contribute through their physical, hydraulic, and pozzolanic activity to improving the behavior of cements in both the fresh and hardened states. Several types of additions are well known, such as natural pozzolans, fly ash, blast furnace slag, and silica fume. These products become more active in the alkaline solutions of cement and give rise to new hydrates that impart greater mechanical strength and better durability to concretes. Through their surface activity and granular distribution, they play a fundamental role in the rheological and mechanical behavior of mortars and concretes. Quarry waste sand (QWS) is generally stockpiled to be eventually sold at very low prices. For this reason, its use in the production of concrete and mortar is increasingly becoming a necessity to protect the environment and meet the needs of the construction and public works sector.This study aims to investigate the effect of using both supplementary cementitious materials (SCM) and quarry waste sand(QWS) to improve some properties of mortar. Ordinary cement is replaced by 10%, 20% and 30% of silica fume (SF), natural pozzolan (NP) or ground blast-furnace slag (GBFS) by weight and the properties of the QWS sand -based mortar are compared to those of natural sand (NS) based mortar. In this study, the slump, superplasticizer requirement, rheological parameters, mechanical strength, and water absorption are investigated. The results obtained show that QWS sand mix has the best workability and requires less superplasticizer dosage. When SCM were used, a drop-in workability is shown and more superplasticizer is required. Also, QWS sand makes the mortar strength 2 and 1.5 times higher than that of NS and becomes 42% higher with 10% SF. Adequate relationships have been established to predict mechanical strengths as a function of test parameters with high correlation coefficient and low root mean square error.

Effect of incorporation of calcined sediments and perlite as partial cement replacement on mortars behavior

The accumulation of sediments in varied dams built in Algeria denotes a vital problem that requires immediate attention and action from the authorities and managers of the National Agency for Dams and Transfers (ANBT). More than that, various research studies on sediments have revealed that subjecting them to heat treatment can exploit these sediments as a viable substitute for some of the cement used to produce cementitious materials. Combining the different types and quantities of natural Perlite pozzolan can achieve many benefits, including reduced consumption, minimized heat generation, improved workability, reduced permeability, and increased strength. This study aims to explore the potential of using dredged sediments from Chorfa II dams and perlite from Hammam Boughrara (located in western Algeria) as substitutes for cement in mortar analysis. A thorough examination of calcined sediments and perlite revealed the feasibility of partial cement replacement. Research has mainly focused on evaluating the properties of mortars in fresh and hardened states.

A new method for improving the resistance of cement-based materials to carbonic acid water corrosion: Carbonation curing and further water curing

Accelerated carbonation curing has several advantages compared with traditional moisture curing in terms of decreasing the duration time of early curing and improving the mechanical properties, dimensional stability and durability of concrete. This study investigated the effect of accelerated carbonation curing and further water curing on corrosion behavior, corrosion products, and pore structure of cement mortar and paste samples exposed to carbonic acid water corrosion. The results indicate the accelerated carbonation curing reduces corrosion depth and mitigates the decline in compressive strength caused by carbonic acid water corrosion. The accelerated carbonation curing can lead to the decalcification of C-S-H gel, and the formation of a large amount of CaCO3 and silica gel (SiO2·γH2O) on the surface of the C-S-H gel, which play a crucial role in the corrosion resistance of carbonic acid water. CaCO3, firstly, fills pores and optimizes the pore structure, slowing down the diffusion rate of carbonic acid water. Meanwhile, an essential "protective layer" forms on the surface due to abundant CaCO3, effectively preventing further corrosion of internal C-S-H gel, CH, C2S, and C3S. At the later age of corrosion, the carbonic acid water can lead to the decalcification shrinkage of CaCO3, and the deterioration of pore structure, which adversely affects the mechanical properties of cement-based materials.

Investigation of gradient properties for cement mortar interfacial transition zones and their effects on mechanical characteristics using micro-CT

The interfacial transition zone (ITZ) in cement-based composites with aggregates is widely recognized as the most vulnerable component, greatly affecting their physical and mechanical properties. In this study, the effect of the ITZ characteristics on the mechanical behavior of cement mortar using its actual microstructure was investigated with image-based numerical approaches in this study. The volumetric information of the ITZ of the mortar sample was obtained and characterized from high-resolution synchrotron micro-computed tomography (micro-CT) images. The mechanical properties of the mortar were evaluated using the finite element method, based on the components characteristics represented by grayscale information of the micro-CT images. It was found that the adhesion between the aggregates and binder was well replicated in the simulation with the multiple-phase model, based on the gradient characteristics and properties of the ITZ. Considering the ITZ thickness according to the aggregates size, a more realistic crack propagation trend can be observed. The obtained results confirmed the significant influence of the ITZ thickness and phase distribution characteristics on the mechanical properties of cement mortars, emphasizing the importance of considering ITZ phases for accurate material analysis.

Symbiotic impact of carbon quantum dots on microstructural development and mechanical behaviour of cement mortars

Carbon Quantum Dots (CQDs) are a new environmentally pleasant material of the carbon family that has gained great interest in construction engineering due to their unique and valuable properties, such as high stability, minimizing toxic activity, and good water solubility. Therefore, this study aims to synthesize the CQDs using glucose as a precursor and apply it as nano-reinforcements in cement mortar. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and transmission electron microscopy (TEM) technologies were used to characterize the generated CQDs. The mechanical properties of the created CQDs-cement mortar were investigated by assessing the compressive and flexural strengths as well as the workability of the mortar samples. Experimentally, four different percentages of the developed CQDs— ranging from 0.005% to 0.030%—were added to the cement mortar. The acquired results showed that, at the age of 56 days utilizing 0.025% CQDs, the compressive and flexural strengths of the CQDs-cement mortar had grown by 72% and 59%, respectively. The workability study's findings revealed no evidence of a significant impact of CQDs on the mortar's flow characteristics. In conclusion, the findings of this study may suggest that CQDs can be used to enhance the mechanical properties of materials based on cement.

Interfacial Behavior of Slag, Fly Ash, and Red Mud-Based Geopolymer Mortar with Concrete Substrate: Mechanical Properties and Microstructure

Geopolymer, as a new type of solid waste-based inorganic cementitious material, exhibits outstanding behavior in terms of physical and chemical performance, macromechanical properties, long-lasting stability, and features potential application development tendency in the field of repair and reinforcement of existing concrete structures. This paper investigated the interfacial behavior of geopolymer mortar with OPC concrete substrate under different slag, fly ash and red mud mixing proportions, while cement mortar was used as a control group for the research. The interfacial bonding properties of the geopolymer mortar to the OPC concrete substrate were elaborated by carrying out split tensile test, double-sided shear test, and three-point bending test. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to further analyze the microstructural characteristics and physical phase components of the interfacial transition zone between the geopolymer mortar and the OPC concrete substrate. The results indicated that the compressive strength of slag-fly ash-red mud-based geopolymer mortar under different mixing ratio conditions was consistently superior to that of cement mortar, where the optimum mixing ratio for the geopolymer mortar was S33F33R33. Overall, the interfacial bonding properties of the geopolymer mortar to the OPC concrete substrate gradually increased with the increment of the slag content, however, an evolutionary trend of minor enhancement followed by a gradual reduction was observed with the growth of the fly ash and red mud content.

High-temperature behavior of zeolite-containing mortar. Experiment and modelling

High temperature experiments were carried out on cylindrical-shaped specimens of mortar containing different concentrations of either cement-replacing zeolite or aggregate-replacing zeolite. The behavior was compared with that of plain mortar. Furthermore, finite-element models were designed, based on material characteristics obtained on the real specimens, to test the temperature exposure effect when similar conditions were applied.

Toughness of Natural Hydraulic Lime Fibre-Reinforced Mortars for Masonry Strengthening Overlay Systems

Masonry structures are susceptible to damage and collapse due to seismic actions, a problem in many urban areas. To address this issue, researchers are studying the use of fibre-reinforced mortars as overlay strengthening systems. This study assessed the use of synthetic polyacrylonitrile (PAN) fibres as reinforcement of natural hydraulic lime mortar, focusing on their influence on fresh behaviour and mechanical properties. Natural hydraulic lime (NHL) was chosen for its compatibility with typical older ceramic and natural stone structural masonry and contemporary ceramic brick infill masonry substrates, as well as for the sustainability benefits. The study also assessed the contribution of the PAN fibres to toughness enhancement in the developed formulations. The fresh behaviour of fibre-reinforced mortar (FRM) was found to be adequate for applications with fibre volume fractions below 0.50%. The compressive and flexural strengths were affected differently by the increase in fibre volume fraction, with compressive strength decreasing and flexural strength increasing. The maximum compressive strength of 13.3 MPa was obtained for 0.25% of fibres, while for flexural strength a maximum of 6.70 MPa was achieved with 1.00% of fibres. The compressive and flexural toughness, related to the post-cracking responses, increased with the fibre fraction, and even for fractions as low as 0.25%, an important increment of the capacity to dissipate energy was achieved.

Physical-mechanical behavior of workable mortars with Perna perna mussel shell as fine aggregate

Cultivation of mussels stands as a significant economic activity in coastal regions Brazil. Often disregarded as waste, mussel shells (MS) possess properties that can be harnessed in the production of building materials. This study explores the utilization of large amounts of Perna perna MS as fine aggregates for the production of fluid mortars. Key parameters such as compressive strength, bulk density, water absorption and void ratio were evaluated. Specimens were prepared according to a full factorial design, with variations of MS content (%MS) (45 to 65 vol%) and water-to-cement (w/c) ratio (0.40 to 0.50). The resulting fluid mortars exhibited satisfactory strength, minimal segregation, and low void content with compactness at the aggregate-cement paste interface. The increase in %MS contributed to higher mortar bulk density but led to reduced void ratio, compressive strength, and workability. The incorporation of a superplasticizer (SP) significantly improved the matrix by enhancing the dispersion of cement particles, mitigating the adverse effects of reduced cementitious material, and enhancing strength. The influence of w/c on compressive strength was found to be 1.6 times greater than that for %MS, while its impact on void ratio was 0.5 times smaller. The full factorial model effectively predicted the mix design for MS-added mortars, yielding strengths ranging from 12 to 21 MPa and void ratios from 21 to 34%.

Capacitive compressive stress self-sensing behavior of cement mortar and its dependence on the thickness

Capacitance based compressive stress/strain self-sensing properties and its dependence on thickness is presented for the fist time. Coplanar electrode configuration is used for the electrical measurements and known weights are used to create cyclic stresses on the mortar samples with different thicknesses. Mortar plates with 6 mm, 10 mm and 15 mm thicknesses are produced and capacitance change with stress application is measured with an inductance-capacitance-resistance meter (LCR meter). Capacitance value of the mortar with 6 mm, 10 mm and 15 mm thicknesses are 450 pF, 532 pF and 607 pF, respectively. Capacitance increases as thickness increases. However, stress sensitivities of the mortar with 6 mm, 10 mm and 15 mm thicknesses are measured as 3.1 × 10–6 P−1, 3.1 × 10–7 P−1 and 1.1 × 10–7 P−1. Stress sensitivity decreases with increasing the mortar thickness. While capacitive self-sensing is effective when the mortar thickness is known, capacitive self-sensing is ineffective with varying mortar thickness. This research contributes valuable insights into the practical application of capacitance-based sensing in materials subjected to compressive stresses, highlighting the need for considerations regarding thickness variations in real-world applications such as load monitoring and weighing.

Influence of recycled rice husk ash filler on the mechanical performance of asphalt mixtures: A mortar scale analysis

Using industrial or agro-industrial wastes as alternative raw materials to manufacture asphalt mixtures brings advantages such as conserving natural resources and reducing environmental problems. Among these wastes are (a) rice husk ash (RHA) and (b) recycled rice husk ash (RRHA), obtained by controlled and uncontrolled combustion of rice husks, respectively. Previous studies have shown a high potential for RHA to be used as a filler in asphalt mixtures. However, the existing literature on RRHA usage and its corresponding applications is limited. Based on this background, the main objective of this study was to investigate the effects of RRHA when used as a filler on the mechanical properties of asphalt mortars/mixtures. For this purpose, the behavior of asphalt mortars (a combination of asphalt binder blended with sand and RRHA filler) was evaluated using the dynamic mechanical analyzer (DMA) with the three-point bending test. The test results suggest that RRHA reduces the workability and ductility of asphalt mortars. Furthermore, while RRHA indicated superior moisture-damage tolerance, brittle RRHA asphalt mortars with reduced fatigue strength were also produced. The optimum RRHA dosage for optimizing the asphalt mortar's mechanical properties/performance should not exceed 13.5% on the total weight of the mortar for the materials and test conditions. As a supplement to this study's findings, further research involving the combination of RRHA with conventional fillers and different materials (i.e., asphalt binders and aggregate types) is suggested to quantitatively assess the scaled-up mechanical performance of the asphalt mortars and their subsequent validation in asphalt mixtures.

Effect of White-Portland cement containing micro and nano silica on the mechanical and freeze-thaw properties of self compacting mortars

This study concentrated to investigate the influences of white-Portland cement (W-PC) containing silica fume (SF: micro-silica (µSi) and nano-silica (nSi)) as replacement (2–4 wt%) on mechanical (strength and durability), physical and microstructural behaviors of self-compacting mortars (SCMs) fabricated at 0.48–0.63 w/b ratios. In keeping with these purposes, besides of carrying out the workability (mini-slump flow: M−SF and V-funnel: V-F) experiments of SCMs, the mechanical and microstructural tests implemented were: unconfined compressive strength (UCS), flexural strength (FS), freeze–thaw (F-T) and scanning electron microscope (SEM) analysis. The outcomes displayed that, in comparison with the control, replacing W-PC by SF (particularly nSi) enhanced the UCS and FS, resisted against F-T durability by lowering the strength losses in UCS and FS. The ameliorated microstructure resulting in a reduction in the number and/or a narrowing in the size of micro-cracks and pores contributed to generate a more compact and consolidated SCM structure for the improving of strength and durability due of pore-filling effect and superior pozzolanic characteristics of µSi and especially nSi, this in turn reduced the permeability of SCM, which has a significant effect on the strength and durability behaviors of the SCM.

Assessment of self-healing behavior of polypropylene fiber-reinforced cement mortar with crystalline admixture: the effects of crack widths, cracking ages, and external conditions

Crystalline admixture (CA) is an effective self-healing agent for mortar. However, the effects of crack parameters (i.e. crack width and cracking age) and the service environment on the self-healing behavior of CA-containing mortar are not well understood. Herein, the self-healing behavior of mortar containing a self-developed CA was assessed by testing strength recovery, impermeability recovery, and crack closure in pre-cracked specimens. Three initial crack widths (0.2, 0.3, and 0.4 mm), five cracking ages (3, 7, 14, 28, and 56 days), and four external exposure conditions (humidity chamber, air exposure, water immersion, and wet-dry cycles) are investigated. Furthermore, the influence of different external conditions on the healing products at the region of crack and the pore structure of hardened paste containing CA are studied. The results show that adding 4.54% CA into mortar allows rapid healing of 300 μm-wide cracks. Although wider cracks (400 μm) are more difficult to heal, the sorptivity coefficients of the mortars with 400 μm-wide cracks after healing decrease. When the cracks are produced at an earlier age, the pre-cracked specimens have higher recovery ratios of strength and impermeability after healing, and the specimens pe-cracked at a later age still have acceptable compressive strengths after healing. The analysis shows that the strengths and impermeabilities of pre-cracked mortars containing CA exposed to the four external conditions are all recovered. The best self-healing performance is observed for the specimens exposed to water immersion and wet-dry cycles conditions. Somewhat less good self-healing was observed in the specimens exposed to humid chamber condition, while the worst self-healing performance was in the specimens exposed to air exposure condition. This study provides a theoretical basis for the application of novel CAs in cement-based materials.

Evaluation of tensile properties and cracking potential evolution of fly ash-cement mortar at early age based on digital image correlation method

The early-age tensile properties and shrinkage behaviors of mortar are important to investigate its early-age cracking potential. This study employs the digital image correlation method to quantify the tensile properties and shrinkage behaviors of fly ash-cement mortars at early age, aiming to reveal the effect of fly ash on the mortar's cracking potential evolution. Fresh mortars with varying fly ash (FA) contents (0%, 10%, 20%, 30%) undergo comprehensive tests, encompassing tensile strength, ultimate tensile strain, plastic shrinkage, mass loss, and damage assessment within 90–180 mins after casting. The results show that FA could enhance early-age ultimate tensile strain and extend the time for the mortar to maintain plasticity while reducing early-age shrinkage strain and mass loss. The mortar's cracking risk is potentially linked to its setting time. The rheological state of mortar gradually changed from plastic to non-plastic after initial setting, and the ultimate tensile strain stabilized, but the shrinkage strain increased rapidly, which resulted in a greater risk of shrinkage-induced cracking. Furthermore, after 180 mins of curing, the damage index of the fly ash-cement mortar (10% FA) was 1.6 times that of pure Portland cement mortar, whereas the damage indexes of the fly ash-cement mortars with 20% and 30% FA contents are approximately equivalent to 82% of the pure Portland cement mortar's damage index. This indicates that incorporating more than 20% fly ash is beneficial in reducing the risk of plastic shrinkage-induced cracking in mortar.

Workability and Compressive Strength Properties of (Fly Ash-Metakaolin) based Flowable Geopolymer Mortar

RPC (Reactive Powder Concrete) is a high-strength concrete with outstanding technical qualities. One of the most crucial critical criteria in RPC development is the cement content. Cement production is seen as an environmentally unsustainable process. As a result, it is necessary to substitute cement in RPC manufacturing with an environmentally acceptable binder. Geopolymer seems to be a novel binder that can completely replace cement. The properties of constituents and their percentages in the mix significantly affect the behavior of geopolymer concrete or mortar. This research aims to produce Geopolymer RPC (GRPC) and verify the impact of the ratios of fly ash/pozzolanic materials (FA/P), sand/pozzolanic materials(S/P), finer sand/fine aggregate (S2/S1), and alkaline solution/pozzolanic materials (A/P) on its mechanical and durability properties. The results of the current works demonstrate that increase in alkaline solution to binder ratio increase the compressive strength of the mortars from 62.28 to 70.01 MPa at 62.50% to 100% alkaline/binder ratio, respectively. As well as, vfor the same alkaline/binder ratio the workability subsequently improves from 15 to 17.3mm.

Investigation of mechanical behavior of mortar using slag as partial replacement of sand based on experimental and machine learning approaches

Investigation of mechanical behavior of mortar using slag as partial replacement of sand based on experimental and machine learning approaches