Decrease In Compressive Strength Research Articles

Optimization of Hybrid Microwave Curing Approach Based On the Performance of Metakaolin-Based Geopolymer Mortars

Geopolymer binders have been highlighted due to their low carbon emission during production and processing. While metakaolin and F-type fly ash are commonly used as raw materials for aluminosilicate-based geopolymers, the long heat-curing requirements for hardening and strength development still pose challenges. This paper investigates the possible use of a hybrid microwave curing technique to design a set-on-demand approach to reduce the duration of heat curing in metakaolin-based geopolymer. The experimental design was established for samples with three different molar ratios (MR; 1.3,1.5, and 1.7) containing metakaolin, fly ash, and silica fume. Samples were subjected to 3 different curing regimes: oven curing, microwave (MW) curing, and hybrid curing (a combination of optimized microwave and oven curing). The performance evaluation was based on compressive strength, dimensional stability, and alkali leaching (efflorescence). Implementing only MW curing resulted in a significant decrease in compressive strength compared to their counterpart oven-cured samples. The reduction of compressive strength was more pronounced at lower molar ratios. The design of a hybrid curing approach where a portion of oven curing was replaced by MW resulted in a higher strength development than those only cured with MW. Similarly, the efficiency of hybrid curing was more pronounced in samples having MR of 1.5 and 1.7. Using MW curing in the geopolymer binders did not affect the alkali leaching; however, it increased the material’s drying shrinkage. Results showed that replacing a portion of oven curing with microwave curing in a hybrid approach can increase the operation speed and the hardening rate without significantly decreasing compressive strength.

An experimental assessment of fracture parameters and microstructure of concrete exposed to calcium leaching

This study delves into the intricate dynamics of calcium leaching in concrete, employing a comprehensive approach to evaluate its impact on structural durability. Accelerated calcium leaching tests, conducted in NH4NO3 solution with a constant pH under controlled conditions, simulate real-world scenarios. Using methods based on degraded thickness and calcium ion concentration, the study determines the acceleration factor, revealing the material's susceptibility to leaching. The chemical composition of the concrete is analyzed using SEM-EDX and XRD patterns with an energy spectrometer. A detailed examination of 145 concrete beams through Three-Point Bending tests over 150 days demonstrates a proportional decline in fracture toughness and tensile strength by 46.6 % and 44.2 %, respectively. A significant correlation emerges between calcium leaching and the reduction in fracture energy, with a 57.5 % decrease observed after 150 days, while compressive strength decreases by up to 38.57 %. This study introduces novel formulations for fracture parameters of leached concrete by employing the boundary effect method (BEM) to connect with concrete microstructure. This represents a pioneering advancement in fracture mechanics and provides a fresh perspective on understanding and addressing the structural effects of calcium leaching in concrete structures.

Assessment of Borač-Kotlenik magmatic massif rock mass technical properties as potential source for optimal development of regional road infrastructure based on local stone materials

The Borač-Kotlenik magmatic massif in central Serbia is mainly made up of effusive and pyroclastic rocks, formed in three main phases of volcanic activity: 1. dacite and andesite, 2. quartz-latite and dacite, and 3. basaltoid rocks. Rock mass samples from this magmatic massif have been examined and mined in numerous localities during the XX century for purposes of building and reconstruction works of local and regional road networks. The examination process continues today for purposes of ‘Morava corridor’ highway building and its demand for the local stone material of the specified quality. The results of rock mass technical properties' tests have shown that its quality for road building purposes depends significantly on petrologic type, soundness, and hydrothermal alteration type. Oxidation alteration types can cause a significant decrease in compressive strength, an increase in porosity and water absorption, especially as oxidation chemical processes cause increased susceptibility to weathering, thus making the rock mass unusable in road construction profile layers above the embankment. Testing results demonstrate that effusive volcanic rocks of the Borač-Kotlenik magmatic massif generally can be used in the road building process. For this purpose, it is necessary to select the conformable rock mass zones at each locality, where hydrothermal alteration and weathering products are absent in order to obtain the best available stone material of volcanic origin.

Degradation of Concrete Cement Stone Under the Influence of Aspergillus niger Fungi

The concepts of physical and chemical transformations occurring in cement concrete under conditions of microbiological deterioration can be used to control the processes of the destruction of cement concretes in order to ensure the required durability and to predict the service life of products. The study of changes in the structural and phase composition of cement stone made of Portland cement grade CEM I 42.5N in the process of fungal deterioration for 6 months when moistened, as well as a sample of a concrete wall exposed to fungal microorganisms for 20 years, was carried out. Diffractograms of the studied cement stone samples contain a large number of pronounced narrow peaks and indicate a highly crystalline structure of phases with the presence of an X-ray amorphous phase of calcium hydrosilicates and tobermorite gel in the cement stone. Changes in the structure of cement stone under the influence of fungi are confirmed by the data of a derivatographic analysis. A decrease in the content of calcium hydrosilicates and ettringite, as well as other crystalline phases in cement stone, leads to a decrease in compressive strength by about 15% over 6 months of fungal degradation. Similar changes after 20 years of exposure to microorganisms suggest deterioration in the strength characteristics of concrete.

Comparison of composite resins containing UV light-sensitive chitosan derivatives in stereolithography (SLA)-3D printers

This study produced composite resins by combining acrylate, chitosan (CH), carboxymethyl chitosan (CMCH), hydroxypropyl chitosan (HPCH), and hydroxyethyl chitosan (HECH) to create materials suitable for use in 3D stereolithography (SLA) printers. Tripropylene glycol diacrylate (TPGDA), urethane acrylate (UA), and photoinitiator (Diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (TPO)) were mixed. CH and its derivatives were added separately to the resin to obtain composite resins. The mechanical test results are clear; the optimum TPGDA: UA ratio was 1:1, the cure time was 60 s, and the TPO ratio was 1 %. The optimum viscosity of the resin is 340–350 cP. Hydrophobic/hydrophilic properties of cured composite resins were examined. The addition of CH and its derivatives to the resin caused a decrease in compressive strength. Adding up to 2.5 % CH, CMCH, and HECH to the resin significantly increased the tensile strength of the resin, giving it flexibility. The gel content of cured composite resins was between 97.72 % and 96.11 %. The cured composite resins demonstrated high chemical and solvent resistance to HCl, NaOH, and HF but exhibited limited resistance to toluene and chloroform. The accelerated UV aging test results show that adding CH derivatives to the resin makes the composite resin more prone to photooxidative aging.

Study on the mechanical property and durability of alkali-activated seawater and sea sand recycled aggregate concrete

This study investigates the potential of Alkali-Activated Seawater Sea Sand Recycled Aggregate Concrete (ASSRAC) as a novel sustainable construction material. By utilizing recycled aggregates from construction and demolition waste, seawater, sea sand, and alkali-activated materials such as fly ash and blast furnace slag, this innovative concrete aims to mitigate carbon emissions from cement production and optimize resource usage. The impact of recycled aggregate replacement rate, water-to-binder ratio, and sand type on the compressive strength of ASSRAC was examined through analysis of variance. Cylindrical axial compression and prism flexural tests were conducted to evaluate the long-term performance of ASSRAC under seawater immersion. The results indicate a decrease in compressive strength with higher recycled aggregate replacement rates and water-to-binder ratios, with recycled aggregates being the primary weak link. Additionally, increasing the water-to-binder ratio hampers hydration by diluting alkali activators, weakening polycondensation reactions. Under seawater immersion, ongoing reactions foster denser C-(A)-S-H structures, enhancing compressive strength and elastic modulus over time. Moreover, higher recycled aggregate replacement rates result in improved ductility, attributed to reactions between the old mortar on recycled aggregate surfaces and slag/fly ash at interfaces. For specimens immersed for 0 and 90 days, most theoretical models accurately predict results, except for the CEB-FIP model, which only accurately reflects the stress-strain curve at 180 days. The seawater-sea sand group's flexural strength initially exceeds that of the freshwater-river sand group due to accelerated early hydration, but this advantage diminishes over time due to high salt content.

Sustainable utilization of phosphorus-rich sludge in cement composites: Multiscale evaluation and mechanistic analysis

The treatment of sludge poses challenges for resource utilization and environmental protection, and utilizing sludge as supplementary cementitious materials (SCMs) presents a viable solution. However, the phosphorus content significantly influences the cement hydration process. This study primarily investigates the feasibility of phosphorus-rich sludge (PRS) as SCMs and examines the effects of combining PRS with calcined clay on cement hydration. The research focuses on hydration heat, mechanical properties, microstructure, and durability of composites comprised of PRS, limestone, calcined clay, and ordinary Portland cement. The results indicate that PRS delays early hydration reactions, leading to a decrease in early compressive strength; after 7 days, the compressive strength is approximately 14.3 MPa (sample S20C10L15). However, over time, the strength increases to 34.1 MPa at 28 days, reflecting a 138.5 % increase compared to the 7-day compressive strength (with sample OPC exhibiting only 69.1 %). This correlates with the hydration exothermic peak occurring in the later stages and the transition of phosphorus's effect on cement hydration from inhibitory to non-inhibitory. The phosphorus in PRS partially replaces silicon atoms in C-(A)-S-H gel, forming C-S(A,P)-H gel. This process refines pore sizes within PRS cementitious materials, enhancing compressive strength over time. Early hydration inhibition and the subsequent pozzolanic reaction of PRS reduce portlandite content, which lowers carbonation durability and thermal expansion coefficient. However, the quaternary blend of PRS, limestone, calcined clay, and ordinary Portland cement demonstrates excellent mechanical properties. This study provides experimental evidence for reducing the environmental impact of PRS and exploring carbon reduction strategies in the cement industry.

Valorization of Different Clays Used in the Treatment of Oily Wastewater in the Development of Construction Products

AbstractThe aim of this research is to study the feasibility of using clays used in the decontamination of wastewater containing olive oil wastewater (OOW), new lubricating oil (NOW) or motor oil (MOW) in the manufacture of ceramic bricks. Three types of clays were used for filtration, kaolinite type clay (KT), smectite type clay (CT) both from Tunisia and illitic chloritic clay (CS) from Jaén (Spain). These clays containing different types of oils, as well as the control clays, were used in the manufacture of bricks fired at 900 °C. These bricks were characterized by physical, mechanical and thermal tests. The sintered microstructure’s evolution was followed by tracked through scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The results indicate that the specific type of clay used influences the technological characteristics of the bricks. The use of CT clay gives rise to increase bulk density, greater compressive strength, and reduced apparent porosity and water absorption. The use of clays used in the decontamination of water containing oils produced a decrease in bulk density, compressive strength and thermal conductivity and leads to an increase in apparent porosity and water absorption in the order OOW > NOW > MOW according to the total organic carbon content (TOC). Therefore, the use of clays used in the filtration of water that contain different oils can represent a promising way of valorizing this waste, which can alleviate the environmental impact and represents economic savings for the industry of construction materials with properties of thermal insulation, getting closer to a circular economy.

Effect of cenospheres on the proprieties of plain concrete exposed to elevated temperature

AbstractThe main objective of the study was to determine the effect of the use of cenospheres for C30/37 class concretes used in construction and road construction. As part of the research, four concrete mixtures were designed: three with the addition of cenospheres and one reference mixture, without the additive. In the three modified mixtures, 20, 40 and 60% of fine aggregate were replaced by cenospheres, respectively. Selected features of the mixtures were determined—consistency and density, as well as the strength properties of concrete. Strength tests were carried out after 28 and 56 days of maturation. Experimental tests of concrete after initial thermal treatment were also carried out at three selected temperatures: 300, 500 and 700 °C, with loading times ranging from 60 to 180 min. These times were selected in such a way that the samples could be heated in their entire volume. A separate group of experimental studies was microstructure studies, the aim of which was to assess the changes occurring in concrete under the influence of high temperatures and to try to justify why CS-I concrete containing cenospheres in the amount of 20% of concrete subjected to annealing at 300 °C has a higher compressive strength than the corresponding reference concrete. The negative influence of cenospheres on the strength of concrete after initial thermal treatment was unequivocally demonstrated. An increase in the amount of cenospheres causes a decrease in compressive strength. A similar negative relationship was also demonstrated in the case of non-heat-treated samples. Graphical Abstract

Drying Shrinkage Properties and Engineering Performance for Cement Mortar Containing Bamboo Biochar Powder (BCP)

Drying shrinkage, the reduction in volume as a material like cement mortar dries, can result in cracks and decreased durability. Bamboo biochar powder (BCP) serves as a substitute for cement in mortar, affecting its drying shrinkage characteristics. Research has shown that BCP in cement mortar can alleviate drying shrinkage by absorbing and retaining moisture. This study aims to assess the chemical and physical properties of BCP, determine the mechanical attributes of bamboo biochar mortar with varying percentages of cement replacement, and investigate the impact of BCP on mortar shrinkage in indoor and outdoor tropical conditions. BCP, derived from Gigantocholoa Abociliata species and sized at 75 µm, was used to replace cement rates of 0%, 5%, 10%, 15%, and 20%. Sixty cube samples (50x50x50mm) were employed for density, ultrasonic pulse velocity (upv), compressive strength, and water absorption tests. Additionally, thirty prism samples (100x100x400mm) were employed to assess drying shrinkage during outdoor and indoor exposure, spanning up to 150 days. The experimental data indicates a consistent trend as the percentage of cement replacement increases in the mortar mix, density, and compressive strength decrease, while UPV and water absorption increase. The lowest shrinkage strain was observed during indoor exposure with 5% cement replacement, attributed to BCP acting as a filler, creating strong bonding properties, and reducing shrinkage. Conversely, the highest strain was noted during outdoor exposure with 20% cement replacement, resulting from higher moisture loss. In summary, a 5% replacement of cement with BCP in mortar offers the most effective reduction in shrinkage strain.

The effect of specimen size on the unconfined compressive strength of cement-stabilized granular mixtures made of natural and recycled aggregates

The cement-stabilization technique is employed on natural and recycled granular materials to improve their mechanical properties. The strength of these materials is assessed by the unconfined compressive strength on laboratory compacted specimens, typically after 7 days of curing. Standards and technical specifications specify different values of specimen height and diameter and different loading modes of testing. This makes the comparison between different materials and with the acceptance limits of technical specifications difficult. The research investigates the effect of specimen size and loading mode on the unconfined compressive strength of both natural and recycled cement-stabilized granular materials. The results revealed significant differences in strength due to variations in specimen size and loading mode. As expected, an increase in specimen slenderness resulted in a decrease in compressive strength. A linear regression model was developed to quantify the effect of the experimental variables on the compressive strength of the two cement-stabilized materials.

The Influence and Mechanism of Polyvinyl Alcohol Fiber on the Mechanical Properties and Durability of High-Performance Shotcrete

This study investigates the impact of polyvinyl alcohol (PVA) fibers on the mechanical properties and durability of high-performance shotcrete (HPS). Results demonstrate that PVA fibers have a dual impact on the performance of HPS. Positively, PVA fibers enhance the tensile strength and toughness of shotcrete due to their intrinsic high tensile strength and fiber-bridging effect, which significantly improves the material’s splitting tensile strength, deformation resistance, and toughness, and the splitting tensile strength and peak strain have been found to be increased by up to 30.77% and 31.51%, respectively. On the other hand, the random distribution and potential agglomeration of PVA fibers within the HPS matrix can lead to increased air-void formations. This phenomenon raises the volume content of large bubbles and increases the average bubble area and diameter, thereby elevating the pore volume fraction within the 500–1200 μm and >1200 μm ranges. Therefore, these microstructural changes reduce the compactness of the HPS matrix, resulting in a decrease in compressive strength and elastic modulus. The compressive strength exhibited a reduction ranging from 10.44% to 15.11%, while the elastic modulus showed a decrease of between 8.09% and 12.67%. Overall, the PVA-HPS mixtures with different mix proportions demonstrated excellent frost resistance, chloride ion penetration resistance, and carbonation resistance. The electrical charge passed ranged from 133 to 370 C, and the carbonation depth varied between 2.04 and 6.12 mm. Although the incorporation of PVA fibers reduced the permeability and carbonation resistance of shotcrete, it significantly mitigated the loss of tensile strength during freeze–thaw cycles. The findings offer insights into optimizing the use of PVA fibers in HPS applications, balancing enhancements in tensile properties with potential impacts on compressive performance.

Study on Dynamic Mechanical Properties and Failure Pattern of Thin-Layered Schist

This paper studies the effect of schistosity on the dynamic mechanical properties and failure pattern of thin-layered schist. Wudang Group schist with thin layers is selected as the research object, and the influence of the dynamic mechanical properties and failure pattern of schist under different angles and spacing is studied by combining an SHPB test and numerical simulation. The results indicate that under dynamic loading, the stress–strain curve demonstrates elastic compression, plastic deformation, and strain softening stages. Moreover, it is observed that the dynamic critical failure strength of schist exhibits typical “U”-type strength anisotropy. Specimens with a schistosity angle of 0° or 90° exhibit higher dynamic compressive strength under dynamic loading, with axial splitting and schistosity splitting as predominant failure modes. Conversely, when the schistosity angles are 30°, 45° or 60°, there is a noticeable decrease in compressive strength accompanied predominantly by shear failure along with local compressive shear failure. We additionally noted that as the spacing between schists decreases from 22 mm to 7 mm, there is a gradual reduction in dynamic compressive strength by approximately 20.3%.

Characteristics of dynamic mechanics and energy loss in reef limestone concrete during dry-wet carbonation periods

Coral reef limestone is a unique type of rock and soil body characterized by high porosity. Its dynamic mechanical properties under impact loads differ significantly from those of conventional land-sourced aggregate concrete.This study utilizes coral reef limestone as both coarse and fine aggregates to prepare C40 strength concrete. The research investigates the effects of dry-wet carbonation cycles on its dynamic mechanical behavior and energy evolution characteristics using a Split Hopkinson Pressure Bar (SHPB) mechanical testing system.The findings reveal that increasing the number of dry-wet carbonation cycles leads to a significant weakening of the internal structural bonding in coral reef limestone concrete. Notably, the degree of phenolphthalein color change diminishes, while uniaxial compressive strength and tensile strength demonstrate an overall downward trend. The reduction in tensile strength is less pronounced than the decrease in compressive strength. Additionally, the relative dynamic elastic modulus gradually decreases, and a size effect is noted, with a rapid acceleration in mass loss. As the number of dry-wet carbonation cycles increases, dynamic compressive strength declines, and failure modes shift from surface cracking to crush-type failure.The dynamic increase factor (DIF) of the coral reef limestone concrete indicates a high sensitivity to strain rate, with a significant rise in DIF value as the strain rate increases. Various energies generated under impact load exhibit clear strain rate effects. Furthermore, the effects of dry-wet carbonation cycling enhance energy dissipation, especially at 30 cycles, where energy dissipation increases sharply, while a hindering effect on transmitted energy is observed.

Biocidal properties of gypsum stone modified with Reynoutria sachalinensis raw materials

The current stage of the construction industry development implies increased requirements for building materials to maintain and improve global environmental processes. The understanding by ecologists globally of the danger of anthropogenic impact on the global environment has been reflected in the formulation of Sustainable Development Goals (SDGs). Thus, scientists and engineers are turning to safe plant-based raw materials as innovative building materials. Of particular interest for practice is the use of Reynoutria sachalinensis, which may exhibit biocidal properties. The purpose of this study was to obtain a gypsum stone modified with an extract from the green mass of R. sachalinensis, as resistant coating to fouling by microscopic fungi. The results indicated 10% decrease in the required water addition to gypsum paste when using plant extract, a slowdown of the initial and final setting time of the modified gypsum paste samples compared to the control samples by 6 and 7 min, respectively, and a slight decrease in bending and compressive strengths of the samples of 12.5% and 6%. The 100% resistance of the modified samples to fouling by microscopic mould fungi was also revealed.

Manufacture and study the mechanical, thermal and physical properties of plastic wood

Abstract This study focuses on evaluating the mechanical properties and thermal conductivity of unsaturated polyester (UPE) composites reinforced with Pistacia shells (Pi-S). Wood-plastic composites were prepared using UPE reinforced with Pi-S at different weight ratios (50%, 60%, 70%). The main objective of this work is to recycle Pistacia shells in significant proportions and assess the impact of using Pi-S as reinforcing materials in UPE. Mechanical tests, such as Shore D hardness, impact resistance, and compressive strength, were employed to evaluate the mechanical properties of the composites. The results showed that the 50% weight ratio achieved the highest values in all tests compared to other ratios (60%, 70%). Impact resistance increased to 10.15 Kj/m2 at the 50% weight ratio, followed by the 60% weight ratio with the highest impact resistance. The results also indicated a slight decrease in Shore D hardness with an increase in the weight ratio and a decrease in compressive strength. Regarding thermal conductivity, the highest thermal conductivity value was at the 50% weight ratio, with a value of 0.68118762 W/mk. It then decreased at the other weight ratios but remained higher than the thermal conductivity of pure unsaturated polyester. This technique allows for the full utilization of Pistacia shells in the wood-plastic industry, contributing to various applications such as wooden and plastic flooring, surfaces, doors, and more.

Investigation on the evolution of concrete pore structure under freeze-thaw and fatigue loads

Hydraulic concrete structures in seasonal frozen regions serve under freeze-thaw cycles and cyclic loading conditions which cause notable alterations in the concrete pore structure and a significant reduction in the mechanical properties and durability of concrete. To understand the macroscopic and mesoscopic damage processes and mechanism of concrete subjected to freeze-thaw cycles and cyclic loading lead, the compressive experiment and computed tomography test of concrete after freeze-thaw and fatigue loading tests were conducted. And the influences of freeze-thaw cycle damage and cyclic loading damage on the pore structure of concrete were analyzed. The relationships between concrete pore fractal dimension, compressive strength, and elastic modulus were revealed. The concrete average pore size can be regarded to grows linearly under freeze-thaw and cyclic loading. The porosity, pore volume, and pore surface area increase with the increase in freeze-thaw cycles, and their relationship can be represented by a quadratic function. However, they first decrease and then increase with the increase of loading cycles after a specific freeze-thaw cycles number. Under the combined action of freeze-thaw cycles and cyclic loading, the non-uniformity degree of concrete pore distribution decreases, and the overall structure is more regular. The distribution of single pore morphology tends to be spherical and banded, respectively. The cyclic loading promotes the extension of the internal pores and cracks of freeze-thaw-damaged concrete which aggravates damage of concrete. Under freeze-thaw cyclic loading, the concrete compressive strength and elasticity modulus is linearly and positively correlated with fractal dimension. With the increase of loading cycles number after freezing and thawing, the fractal dimension and compressive strength decrease, and the elasticity modulus has a larger dispersion. The relationship model between concrete compressive strength and fractal dimension can well describe the macroscopic and mesoscopic evolution of concrete under freeze-thaw and cyclic loading. The results can provide a scientific basis for improving the design and maintenance of concrete and benefit extending the long-term service life of hydraulic concrete structures in cold climates.

Evaluation of Chemical Resistance of Polymer Mortars Containing Biochar

Partial replacement of quartz flour microfiller in polymer composites with biocarbon is one of the potential ways to utilize this waste. The article discusses the possibility of using biocarbon as a component of vinyl ester mortars, in the context of their chemical resistance. The tests were carried out for mortars with different quantitative compositions, and therefore with different biocarbon contents. They were subjected to 12-month exposure to a chemically aggressive environment. Solutions of 0.5% sulfuric acid(VI) and 5% sodium hydroxide were used. Measures of resistance were changes in weight, compressive strength, longitudinal ultrasonic wave velocities and quantitative changes in microstructure compared to chemically unstressed samples. The results show that vinyl ester mortars with biocarbon are more resistant to chemical aggression with sulfuric(VI) acid solution. A significant decrease in compressive strength, ultrasonic wave velocity and an increase in the values of stereological parameters were observed after exposure of the composites in sodium base solution. This is in contrast to the chemical aggression in the acid solution, after which the changes in the properties and microstructural parameters of the mortars were not so clear

Balancing Sustainability and Strength: Analyzing the Effects of Textile, Tannery, and Water Treatment Sludge on Brick Performance

This study investigates the feasibility of incorporating various industrial waste materials, specifically textile sludge, tannery sludge, and water treatment plant sludge, in brick production as a sustainable construction practice. The research analyses the impact of varying sludge proportions on the compressive strength of fired clay bricks. Results indicate an inverse relationship between increasing sludge content and compressive strength across all types. Bricks incorporating higher proportions of textile sludge exhibited a linear decrease in compressive strength, ranging from 0.1 MPa to a low of 0.005 MPa. Similarly, increasing the ratio of tannery sludge to fly ash Class C and Ground Granulated Blast-furnace Slag within the brick mixture consistently corresponded with reduced compressive strength, with a 5:70:25 mix yielding 0.8 MPa and a 40:30:30 proportion resulting in 0.17 MPa. Water treatment plant sludge exhibited a similar trend. A mix proportion of 5:70:25 (sludge: fly ash class C: GGBS) yielded a compressive strength of 1.87 MPa while increasing the sludge proportion to 40:50:10 resulted in a lower compressive strength of 1.20 MPa. These findings underscore the importance of a balanced approach when incorporating industrial sledges in brick production. While beneficial from a sustainability perspective, the observed reduction in compressive strength, particularly compared to conventional clay bricks exceeding 2.5 MPa, necessitates careful consideration. Future research should focus on optimizing mix designs, incorporating performance-enhancing additives, or identifying applications where lower compressive strengths are acceptable to fully realize the potential of these waste materials in sustainable construction.

New Methodology for Evaluating Strength Degradation from Temperature Increase in Concrete Hydration under Adiabatic Conditions

Cement-based construction materials, commonly known as “cement concrete”, result from the hydration reaction of cement, which releases heat. Numerous studies have examined the heat of cement hydration and other thermal properties of these materials. However, a significant gap in the literature is the assessment of the impact of the hydration temperature on the material’s strength, particularly compressive strength. This work presents an experimental methodology that consistently estimates the temperature evolution of a mixture used to manufacture concrete or mortar during the first hours of Portland cement hydration. The methodology aims to ensure results that correspond to an infinite medium (adiabatic conditions), where there are no heat losses to the surroundings. Results obtained under adiabatic conditions (simulating an infinite medium) indicate that a ready-made mortar (Portland cement: sand: water; 1:2.5:0.5) can reach temperatures of approximately 100 °C after 48 h of hydration. Under these conditions, compressive strength decreases by up to 20%.