Compressive Strength Of Mortar Research Articles

Geopolymer using different size fractions of recycled brick-based mixed demolition waste

The hike in CO2 emission from the cement industry calls for an alternative binder to cement. On the other hand, constructionand demolition waste management is a global concern. This research aims to demonstrate the complete applicability of brick-based demolition wastes in geopolymer mortar and concrete. Ground Granulated Blast Furnace Slag (GGBS) was used with brick waste to improve performance. 3 M, 4 M and 6 M NaOH were used for mortar preparation, and 6 M NaOH was used for concrete tests. The performance of the geopolymer binder and mortar was compared with the control specimen. 5 % to 20 % incorporation of demolition waste powder (DWP) with GGBS was explored to find the optimum binder combination. A 10 % incorporation for 3 M and 15 % for 4 M and 6 M was found optimum. Then, 10 % to 100 % incorporation of brick sand was studied to examine the influence of brick-based demolition waste on the fresh and hardened properties of mortar. Sand: Binder: Alkaline activator was taken 3.375: 1: 0.45 for mortar. The workability of mortar varied with the increase of brick sand content. The flexural and compressive strengths were decreased with an increase in brick sand content for all molarities of NaOH; consequently, the water absorption increased with brick sand content. The maximum mortar compressive strength of 27 MPa was found for 10 % demolished sand with a 6 M alkali concentration. However, consistent results were obtained with a 4 M concentration. Geopolymer concrete from brick-based demolition waste was prepared using 6 M NaOH. The UPV result indicates the regular quality of the concrete cube, with acceptable capillary water absorption after 24 h. However, the compressive strength of geopolymer concrete could be useful for non-structural works, and therefore, further studies with higher strength of NaOH for geopolymer concrete are recommended.

Effect of gypsum content in cement on its adaptability to alkali-free accelerator at different temperatures

The setting times and early strength of shotcrete are greatly affected by the gypsum content of the cement used. In this work, the setting times, compressive strength and microscopic analysis (X-ray diffraction quantitative analysis, thermogravimetric analysis and scanning electron microscopy) were used to determine the effects of changes in gypsum content on the hydration and mechanical properties of cement mixed with an accelerator at different temperatures. The results showed that an increase in the gypsum content of the cement promoted the formation of ettringite (AFt) and decreased the setting times of the cement pastes at 0°C, 20°C and 40°C. Mortar compressive strength tests showed that, after curing at 0°C, 20°C and 40°C, the highest compressive strength was exhibited with a final molar aluminate-to-sulfate ratio (C3A/SO3; henceforth called the MASR) of 0.84, 0.84 and 1.18, respectively. The mechanical properties of the hardened cement pastes were adversely affected by MASRs that were too high or too low. When the MASR was too high, the conversion of AFt to monosulfate (AFm) was facilitated and C3S hydration was slowed. Conversely, when the MASR was too low, this enabled large amounts of AFt to occupy the space where calcium silicate hydrate (C-S-H) gels were formed, resulting in decalcification of the C-S-H gels.

Impact of Graphene on Microstructure and Compressive Strength of Cement Mortars Utilizing Two Different Dispersion Methods

Impact of Graphene on Microstructure and Compressive Strength of Cement Mortars Utilizing Two Different Dispersion Methods

Effects of Adding Coal Ash vs Rice Husk Ash on Compressive Strength of Mortar

Coal is widely used as an energy source in several industries, especially for power plants (PLN), but on the other hand this causes waste problems or environmental impacts. Several studies have been carried out to utilize coal ash waste (fly ash) as an additional material [or as a partial substitution material] in making mortar. This research aims to determine the effect of adding coal ash and rice husk ash with variations of 5%, 10% and 15% of cement weight respectively (at ages 3 days, 7 days, 14 days, 21 days and 28 days). on the 'compressive strength' and 'absorption capacity' values of the mortar. This research uses quantitative methods through a series of experiments on 60 samples or test objects with the addition of coal ash (fly ash) and rice husk ash in the mortar mixture with reference to the Indonesian National Standard (SNI 03-6825-2002). Next, a series of tests were carried out at the age of 3 days, 7 days, 14 days, 21 days and 28 days to calculate the ' strong ' value. press' and ' power absorb' mortar. The research results showed that with the addition of coal ash and rice husk ash, the mortar experienced a significant increase in 'compressive strength' when compared to ordinary mortar, the strength of the mortar reached the optimum level at a variation of 15% addition of the cement weight, reaching 240.96 kg /cm 2 . Meanwhile, with the addition of husk ash in the same variation, the compressive strength of the mortar reached 204.82 kg/cm 2 .

Fracture behaviour assessment of high-performance fibre-reinforced concrete at high strain rates using interpretable modelling approaches

High-performance fibre-reinforced concrete (HPFRC), a type of cementitious composite material known for its exceptional mechanical performance, has widespread applications in structures exposed to severe dynamic loading conditions. However, understanding nonlinear HPFRC fracture behaviour, particularly under high strain rates, remains challenging given the complexities of assessment procedures and cost-intensive nature of experiments. This study presents an interpretable framework for modelling and analysing HPFRC fracture strength at high strain rates. A wide range of machine learning methods, including ensemble techniques, were employed to capture multivariate effects of eight essential input features (e.g., mortar compressive strength, fibre physical and mechanical properties, cross-sectional area, and strain rate) on fracture strength response. To assess the derived models, a novel evaluation procedure was proposed involving a data-based analysis, employing established metrics (i.e., coefficient of determination, root mean squared error, and mean absolute error via K-fold cross-validation) and a domain experts-involved evaluation utilising global sensitivity analysis to discern first-order and higher-order interactions among input factors. The proposed approach efficiently yielded both quantitative and qualitative insights into crucial input factors governing HPFRC fracture strength with limited experimental data. The obtained findings highlight the significance of multivariate effects, such as the interaction between strain rate and fibre tensile strength, and between fibre volume and fibre diameter, on fracture behaviour. The proposed interpretable framework aims to provide a powerful tool for proactive material failure analysis by understanding fracture behaviour and identifying potential weak and strong interactions among input factors of HPFRC-based samples. Moreover, the utilisation of the proposed approach enables researchers and civil engineers to efficiently focus on the most critical input parameters during the early design stage and ensuring the structural integrity and safety of HPFRC-based constructions.

An Experimental Study on the Mortar Compressive Strength According to Fineness and Replacement Rate of Limestone Powder

Cement industry emits as much as about 8% of global carbon dioxide emissions, so it is necessary to develop new technologies that can effectively reduce carbon dioxide emissions to prevent global warming and to maintain industry competitiveness. The supplementary cementitious materials that can replace clinkers are limited to fly ash and blast furnace slag in Korea, but various materials such as limestone and calcined clay have been used in other nations. In this study, the characteristics of limestone powder mixed cement were reviewed in consideration of the limestone powder manufacturing process.

A reusable graphene oxide aerogel for pre-concentrating and recovering uranium from water and valorisation of spent material in a cementitious material

Graphene oxide is an excellent substrate for pre-concentrating and recovering uranium in water. However, the need for scalable and affordable methods for producing graphene oxide has hindered its field applications. Besides, a sustainable strategy is required to recycle spent adsorbents and prevent them from entering the waste stream. In these contexts, this paper describes the application of graphene oxide aerogel (GOA) produced from graphite through a single-step combustion route for pre-concentrating and recovering uranium in water. The method allows GOA production in bulk quantity at 8–10 times less cost than prevalent Modified Hummer's graphene oxide (HGO). The paper also demonstrates using spent GOA as an active admixture in mortar to improve its mechanical properties. The physicochemical properties of the GOA and mechanistic details of uranium surface bindings were studied thoroughly. GOA showed enhanced uranium adsorption capacity (278 mg/g) compared to HGO due to abundant hydroxyl, carboxyl, and epoxy groups on GOA. However, the presence of HCO3− in water reduced uranium uptake due to highly water-soluble uranium-carbonate complexes such as (UO2)2CO3(OH)3−,UO2(CO3)34−, and UO2(CO3)22−. The addition of the spent GOA improved the cement mortar's compressive strength by 15 % compared to the pristine cube and arrested the leaching of residual uranium. The GOA addition and associated enhancement in compressive strength help to save cement and lower CO2 emissions. In short, the present work addresses the critical challenges of using GOA in pre-concentrating and recovering aqueous uranium, such as bulk production, production cost, and spent materials disposal.

Assessing the Effects of Water Content on the Unconfined Compression Strength of Egg White-Stabilized Khorasan Mortar

Khorasan mortar, a traditional, durable, and environmentally friendly building material, has been utilized for centuries in the Khorasan region of Türkiye. Its composition, which is based on natural hydraulic lime, imparts exceptional strength, breathability, and workability, making it suitable for diverse construction projects. Consequently, investigating the mechanical properties of Khorasan mortar, specifically its interaction with stone elements in historical buildings, in various mixing ratios, can provide valuable insights into the preservation and future of these architectural treasures. This study focuses on researching Khorasan mortar as a material of interest, utilizing brick ballast, lime, standard sand, water, and egg white, with a particular emphasis on egg white-stabilized Khorasan mortar. Four different water contents (70%, 80%, 90%, and 100%) were carefully selected, based on the dry mass of the egg white, to prepare a total of 12 samples (three identical samples for each water content) for testing. Prior to testing, the samples were cured for seven days in a desiccator. Unconfined compression strength tests were conducted, and axial strain-stress graphs were plotted to determine the unconfined compression strength (UCS) of the mixtures. The results revealed that the mixtures containing 80% water content exhibited the highest UCS values, while the samples with 90% and 100% water content demonstrated similar UCS values. The minimum UCS was approximately 0.518 times the maximum value, suggesting the importance of optimizing the water amount in Khorasan mortar formulations.

Mechanical properties, durability and self-healing performance of mortar containing double-layers capsules

To improve the self-healing performance of cementitious materials and minimize the negative impact of self-healing materials on mortar, a novel type of double-layer capsules is developed in this study. The developed double-layer capsule includes the rapid hardening cement as the internal wall and polyvinyl alcohol (PVA) as the external wall. To evaluate its impact on mortar, two factors (i.e., capsule size and dosage) are considered and the correspondent experiments of investigating mechanical properties, durability, and self-healing performance are conducted. Experimental results present that the double-layer capsules reduce the flexural and compressive strength of mortar. With a reduced capsule size and a small ratio of the dosage, the negative impact the capsule gradually weakens. Moreover, the mixing of capsules slightly decreases the chloride penetration resistance and carbonation resistance of mortar specimens, while improves the frost resistance and impermeability greatly when the dosage is within 10%. Furthermore, the capsules can significantly improve the self-healing capacity of mortar. Especially when the capsule size is 2.36–3.2 mm and the dosage is 10%, the healing effect on matrix is highest. In addition, the XRD\\SEM\\XCT results indicated that the healing products mainly include C-S-H gel, CaCO3, Aft and Mg-containing compounds, the filling and bonding effects of which realize the automatic and effective recovery of matrix properties.

Electric field-induced deterioration of cement mortars owing to calcium leaching

This paper investigated the calcium leaching from plain and fly ash/limestone blended cement mortars under an electric field. The Ca2+ leaching degree and reduced CaO content were measured to assess the extent of calcium leaching, and the compressive strength loss was used as an indicator to evaluate the degradation of the mortars due to leaching. Additionally, the changes in mineralogical composition, micrograph, Ca/Si ratio of C–S–H gel, and pore structure of leached samples were analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS), and mercury intrusion porosimetry (MIP). The findings indicated a notable acceleration in the leaching of Ca2+ due to the application of an electric field. Consequently, the calcium leaching degree of mortars continuously increased with time. The accelerated calcium leaching resulted in the loose microstructure and increased porosity mainly for the cathode part as well as the reduction in compressive strength of mortars. The addition of fly ash was beneficial in reducing the calcium leaching and strength loss of mortars after 90 days of exposure to the electric field, contrary to the effects observed with the incorporation of limestone powders. Attention should be paid to the durability issues of cement-based materials induced by the electric field.

EFFECTS OF COMBINATIONS OF LIMESTONE POWDER AND METAKAOLIN ON MORTAR COMPRESSIVE STRENGTH DEVELOPMENT

Cement production is a major contributor to carbon dioxide (CO2) emissions, and concrete is one of the most widely used building materials in the world. To reduce CO2 emissions from cement, supplementary cementing materials have been widely introduced in mortar and concrete mixtures. This research will explore the mechanism that determines the development of compressive strength in mortar made with partly substituted cement and a mixture of limestone powder and laboratory-quenching heat-treated kaolinite clay (also called metakaolin). Metakaolin is rich in Southeast Asian countries and needs further investigation to adopt in cement systems. Limestone powder and metakaolin constitute 45% of the binding cement ingredient by weight (dry). The strength was evaluated using mortar, and the microstructure was determined using paste. The results show that at 28 days, the compressive strength of mortar containing 45% cement substitution by 15% limestone powder and 30% metakaolin with 1% PCE (per B45S 1:2) was 97% relative to the reference mortar. However, due to the impurities in metakaolin, its synergistic interaction is limited, which results in the compressive strength being lower than anticipated.

Performance of sustainable ternary blended cement containing municipal solid waste incineration fly ash coupled with slag, coal fly ash or metakaolin

Developing low-clinker cements can effectively reduce carbon footprint of the cement industry. Additionally, more sustainable methods over landfilling are needed to tackle the increasing annual generation of municipal solid waste incineration fly ash (IFA). In this study, carbonated-washed IFA coupled with slag (SG), coal fly ash (CFA) or metakaolin (MK) were used to substitute 60 % of Portland cement to form ternary blended cement. Performance of the blended cements was investigated and compared with pure Portland cement in terms of hydration kinetics, binding capacity, hydration mechanisms, pore characteristics, microstructure, and leaching toxicity. Results indicated that in the blended cement systems, ettringite was stabilized by the formation of hemicarboaluminate as a result of the reaction between calcium carbonate in the IFA and aluminate in SG, CFA and MK. The SG displayed the best synergy with IFA, refining pore structure through pozzolanic reaction and increased formation of ettringite and hemicarboaluminate. For an optimal 40 % SG+20 % IFA blended cement, the mortar compressive strength reached 90 % of that for pure Portland cement at 90 days. Although CFA had abundant aluminate, its low reactivity restrained the performance of the blended cement, resulting in poorer pore structure and lower compressive strength. The MK had abundant reactive silicate and aluminate, but the rapid consumption of calcium hydroxide by the pozzolanic reaction and hemicarboaluminate formation restrained further reaction, limiting the performance of the blended cement at the later stage. Besides, the heavy metal leachability and dioxin level in the produced mortar satisfy the prerequisites to be categorized as nonhazardous according to HJ 1134. This study demonstrated the promising potential of the blended cements to simultaneously divert IFA from landfills and reduce the clinker content of cement.

Low‐CO2 cements based on magnesium oxide / hydromagnesite blends – hydration mechanism and mechanical properties

AbstractBinders based on blends of reactive magnesia and hydromagnesite are low‐CO2 or even carbon‐negative cements in case the MgO is generated from magnesium silicates or Mg‐containing brines. When MgO is hydrated with water alone, a well crystalline brucite forms, but no measurable strength is developing. In the presence of hydromagnesite, the hydration of MgO is accelerated and the hydrate assemblage is changed. A poorly‐crystalline brucite containing some carbonate is the main hydration product. Furthermore, a kind of “gel‐water” is observed, which is lost at temperatures above 40‐60°C. This brucite‐like phase is responsible for strength formation in MgO‐hydromagnesite blends. After 28 days, a mortar compressive strength is reached similar to the one of a Portland cement of strength class 32.5.

Smart laying mortars for masonry structures: effects of lime/cement ratio and carbon nanomaterials content on self-sensing behavior

The mechanical behavior of mortar joints directly affects the structural performance and failure mechanisms of masonry. Since previous research did not evaluate the effects of different lime/cement ratios on intrinsic self-sensing properties, this study developed a factorial experiment to investigate the electrical resistivity, gauge factor, stress sensitivity and compressive strength of mortars with different lime/cement proportions (0.25, 0,50, 1.00, 2.00, by volume) and carbon black nanoparticles (CBN) contents (0%, 3%, 6%, 9% by weight of binders). Results were explained based on X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (FEGSEM) analyses. Increases in lime content delayed the percolation threshold and decreased the mortars’ strength. Portlandite and calcite structures of lime increased the distance between CBN, modifying the electron conduction mechanisms. At the end of the percolation zone, the addition of lime increased self-sensing properties, whereas the opposite behavior was observed at the beginning of the percolation zone.

Influence of Temperature–Humidity Sensor Housing Depth on Concrete and Mortar Compressive Strength

Recent advancements in sensor technology have led to an increase in embedding sensors into construction materials for monitoring purposes in the construction industry. However, systematic research on the resulting changes to the material properties is still lacking. A previous study confirmed that the copper–nickel-plated housing of SHT-31 sensors affects the compressive strength of mortar. Moreover, it is necessary to conduct further research to determine if this analogous occurrence takes place in concrete. This study embedded temperature–humidity sensor housings in concrete at 10 mm, 20 mm, and 30 mm, before performing compression tests and a finite element analysis (FEA). The empirical findings indicate that the compressive strengths of concrete at 10 mm, 20 mm, and 30 mm depths were 26.1 MPa, 28.4 MPa, and 29.4 MPa, respectively. In contrast, the control concrete that did not have a sensor housing had a compressive strength of 31.9 MPa. In the case of mortar, a design strength of 28 MPa was achieved at a depth greater than 30 mm, while concrete reached this design strength at 20 mm. Based on these findings, embedding temperature–humidity sensor housings in concrete is recommended at depths greater than 20 mm from the surface. These results serve as important reference data for determining the optimal embedding depth of sensor housings in structures using cement-based materials.

Impact Energy Absorption of Sisal Fiber Reinforced Ferrocement Slab Elements and Its Statistical Relationship with Composite Compressive Strength

This study evaluates the level of energy absorption of sisal fiber reinforced ferrocement (SFRFC) slab elements of size 300 mm × 300 mm × 25 mm) (thickness) through low-velocity impact tests. The slabs are reinforced with 2 and 3 layers of steel weld mesh as primary reinforcement; and the sisal fibers of short and long fiber length, S-FL = 20 mm and L-FL = 40 mm (respectively) of varying volume fraction, (FVf of = 0.25–1.00%) act as secondary reinforcement. The compressive, split-tensile strength and flexural strength of hardened sisal fibrous mortar and plain (control) mortar specimens are determined and presented. The initial impact energy absorption (IIEA) and ultimate impact energy absorption (UIEA) of SFRFC slabs were found to be higher than ferrocement (FC-control) slabs (reinforced with 2 and 3 layers of steel mesh) demonstrating the effective contribution of sisal fibers in improving the performance of ferrocement slabs. When the length of the sisal fibers was increased from 20 mm to 40 mm in SFRFC slab elements (in hybrid combinations of steel mesh of 2–3 layers and fiber volume fraction of 0.25–1%), the impact resistance has increased several-fold over FC-control slabs. The composite compressive strength (CCS) of SFRFC has substantially increased when sisal fibers (of short and long fibers) of fiber volume fraction (FVf = 0.25–1%) are added to FC-control slab elements. Statistical prediction models have been developed separately for three dependent variables, IIEA, UIEA and CCS keeping constant the four independent variables, mesh layers (ML), fiber volume fraction (FVf), fiber length (FL) and mortar compressive strength (MCS), and the predicted values matched with the experimental results, within the acceptable error range. This study has statistically established a significant relationship between UIEA and CCS of sisal fiber reinforced ferrocement (SFRFC) slab elements.

Effects of copper mining wastewater on the performance of waste-based low-clinker cement mortars

The presence of copper mining wastewater (CMw) in wet copper tailings (CTs) significant impediment to the reutilization of wet CTs in cementing material. This paper investigates the influence of CMw on the performance of waste-based low-clinker cement (Lcc) mortars, aiming to address the fundamental issues related to the application of wet CTs. In this regard, four Lcc mortars were prepared by using CMw to replace 0, 25 %, 50 % and 100 % of tap water. The influence of CMw on the setting time, hydration kinetics, hydration products, pore structure, compressive strength and microstructure of Lcc mortars were analyzed. Experimental results show that the addition of CMw prolonged the setting times and retarded the hydration process of Lcc paste due to the presence of acids and organic substances in CMw. Nevertheless, the presence of Ca2+, Na+, and Mg2+ in CMw can accelerate the dissolution of Lcc, contributing to the formation of expansive ettringite and hydrotalcite. As a result, Lcc mortars with CMw possessed denser pore structures. By using 50 % CMw, the compressive strengths of mortars can be increased by 3.5 % at 3d, 5.21 % at 7d, and 8.75 % 28d. The feasibility of adding CMw in Lcc mortars was verified, which would serve as the foundation for the preparing of Lcc-based materials with wet CTs.

Effects of kaolin-modified superabsorbent polymers on mortar properties

This study investigates the impact of kaolin-modified superabsorbent polymers (SAPs) as internal curing agents on mortar properties. While SAPs have been known to mitigate the shrinkage of cement-based materials, their adverse effects on strength have limited their applicability. In this paper, the strength and shrinkage of mortars with varying SAP proportions were measured, along with an assessment of internal porosity and hydration conditions. Results indicate that kaolin-modified SAPs effectively reduce autogenous and drying shrinkages in mortars. Although modified SAPs influenced pore size distributions, resulting in reduced strength, higher content of kaolin composite strengthened the bond between SAPs and cement-based materials. This enhanced the spherical shape of SAPs and facilitated the release of internally stored water through capillary action, thereby increasing the contact area between cement slurry and water. Consequently, mortar hydration was promoted. Moreover, higher acrylamide content in modified SAPs improved alkali and Ca2+ resistance, increased the water absorption ratio, optimized the internal maintenance effect, and reduced the loss of flexural and compressive strength in mortars.

Prospects for the use of fine-dispersed recycling products of concrete processing as mineral additives for the manufacture of building mortars

Introduction. One of the most important reserves for saving material and energy resources in the construction industry is the re-involvement of recycling concrete materials (products of disposal of substandard concrete, reinforced concrete structures and products), in particular, highly dispersed powders with the prospect of their use as a mineral additive for the production of mortars for general construction purposes, in the production field. The implementation of this approach will practically ensure the introduction of the most important principle of waste-free technological processes (in the production of prefabricated and monolithic concrete, reinforced concrete structures and products) and create conditions for solving important economic and environmental problems.Aim. The aim of the work were the determining of the main physical and mechanical characteristics, comparative analysis of the mortar on Portland cement, as well as mortars with the replacement of a part of Portland cement (by 10, 15 and 25 %) with a recycling (concrete) fine powder with a specific surface area of 4500 cm2/g.Materials and methods. For the research, the following components were used: recycling (concrete) fine powder with a specific surface area of 4500 cm2/g, construction sand with a size modulus Mk = 2.31 (according to GOST 8736-2014), portland cement with CEMII/V-W 42.5N (according to GOST 31108-2020) slag, chemical additive “CENTRIPOR TFM 411R”.The selection of mortar compositions was carried out according to SP 82-101-98. Tests of mortar mixtures and mortars were carried out according to GOST R 58767-2019. Compliance with the compressive strength of mortars with the grade was determined in accordance with GOST R 58766-2019.Results. As a result of the work carried out, it is shown that fine-dispersed recycling concrete powder with a specific surface area of 4500 cm2/g can be used as a mineral additive (filler) for the production of mortars on a par with additives currently used in the construction industry of the country.Conclusions. The possibility of using fine-dispersed recycling concrete powder with a specific surface area of 4500 cm2/g as a mineral additive (filler) for the roductionof mortars on a par with additives currently used in the construction industry of the country. It has been shown that when 10 % of cement is replaced with recycled (secondary) fine powder with a specific surface area of 4500 cm2/g, the strength of building mortars of the M100–M150 grades increases and its structure improves.

Effect of artificial interior stone sludge on physicomechanical properties of mortars

Artificial interior stone is a decorative building material, which mostly consists of quartz. Sludge is generated during the stone manufacturing process, and the amount of sludge is increasing due to the high demand; however, most of the generated sludge is disposed of in landfills. In the present study, the effects of the sludge addition on the physicomechanical properties of mortars were investigated via flowability, penetration resistance, mercury intrusion, and compressive strength tests. The independent variable was the replacement ratio of the sludge to the fine aggregate. The test results showed that the addition of the sludge reduced the flowability, and initial and final setting times, while the percentage of the pores involved in the hydrates increased. The compressive strength of mortars with the sludge was improved compared to that of the mortars without the sludge. Quantum chemistry simulations were conducted to understand the strength enhancement mechanism of the specimens, and a straightforward machine learning-based model equation was proposed by applying the experimental variables and measurement results.