Increase In Compressive Strength Research Articles

Long-term Compressive Strength Properties of Concrete Incorporating Admixtures: Outdoor Exposure Testing in a Coastal Environment

In this study, concrete specimens were fabricated based on domestically manufactured materials, and long-term exposure tests were conducted in a domestic coastal environment. This study analyzes the long-term compressive strength characteristics of concrete mixed with admixtures. The mixed materials used were divided into blast furnace slag and fly ash. The blast furnace slag and fly ash were, respectively, produced by replacing ~ 30% and ~ 15% of the cement. The compressive strength was measured at 28 day, 1 year, and 10 years of age and compared with that of ordinary concrete. In addition, the long-term compressive strength results obtained in this study were compared with those of concrete mixed with admixtures reported in the literature. The strengths of the ordinary specimen at 1 year and 10 years of age increased by ~ 10 MPa and ~ 22 MPa compared with those at 28 day of age. However, concrete mixed with admixtures yielded compressive strength increases of ~ 5 MPa and ~ 26 MPa at 1 year and 10 years of age, respectively, compared with those at 28 day of age. A comparison of the compressive strengths of concrete mixed with admixtures reported in the literature (based on age) and those obtained in this study showed that there was an initial strength difference in the range of 10–25%. However, the compressive strength at 10 years of age was almost similar to those reported in the literature with differences of less than 5%. These findings confirmed that when using pozzolanic admixtures, the development rate of the initial strength may vary owing to various factors; however, the long-term strength converges within a certain range.

Construction biotechnology: improving mortar properties through calcium carbonate precipitation using a novel strain of the bacterium Neisseria perflava

In construction technology, there are significant efforts to reduce environmental emissions, particularly NH3 and other pollutants. This study marks the first application of CaCO3 biomineralization biotechnology in microbially induced calcium carbonate precipitation (MICCP) to enhance mortar properties using the non-pathogenic Neisseria perflava strain SKC/VA-3, which employs carbonic anhydrase mechanisms. The results demonstrated that N. perflava could significantly improve the physical and mechanical characteristics of mortar. Incorporating N. perflava and calcium lactate pentahydrate resulted in a 20% increase in compressive strength and a 14% rise in indirect tensile strength of the mortar. Examination through scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM–EDS) revealed calcite formation within the microstructure of the bio-mortar. Additionally, self-healing assessments indicated that calcite precipitation, driven by bacterial metabolism, also occurred on the cracked surfaces of the bacterial mortar, suggesting potential for reduced maintenance and increased material longevity. This study provides the first report on the use of N. perflava for bio-mortar enhancement and represents a novel biotechnological approach to improving the properties of mortar and other cementitious materials. The utilization of N. perflava in bio-mortar represents a groundbreaking biotechnological advance, potentially enhancing mortar and other cement-based materials. This development contributes to sustainable, durable, and environmentally friendly construction technologies.

Microstructural homogenization and mechanical enhancement of aluminum matrix composites via multi-pass friction stir processing with SiC reinforcements

In this study, the environmentally friendly friction stir processing (FSP) method was utilized to fabricate surface composites employing technical aluminum matrix 1050-H14 and aluminum alloy 6060-T4 reinforced with silicon carbide (SiC) particles. Microstructure analysis, employing light and scanning electron microscopy, in conjunction with comprehensive evaluations of hardness, compressive strength, and tribological properties, was conducted to elucidate significant findings. The results reveal that an augmented number of FSP passes contributes to the homogenization of microstructure, leading to the alteration of SiC particle morphology and fragmentation. Consequently, this phenomenon results in improved mechanical properties, particularly noteworthy in the case of AA6060-T4 alloy matrix composites, and enhanced wear resistance. Both AA1050-SiC and AA6060-SiC composites demonstrate notable increases in compressive strength compared to their unreinforced matrices. Particularly noteworthy is the substantial enhancement in compressive strength observed in the AA6060-SiCp composite, escalating from 249 to 331 MPa (at ε = 0.1) and from 398 to 715 MPa (at ε = 0.2) with an increase in the number of FSP passes. Additionally, FSP’s ability to precisely control process parameters such as tool rotational speed and traverse speed allows for the optimization of mechanical properties and microstructural characteristics tailored to specific application requirements. This study highlights the potential of FSP in fabricating high-performance aluminum matrix composites with superior strength and wear resistance, positioning it as a viable technique for advanced engineering applications. The environmentally friendly nature of FSP, due to its solid-state operation and reduced energy consumption, further underscores its suitability for sustainable manufacturing practices.

Analysis of Rock Mechanical Characteristics and Establishment of an Evaluation System for Coal Measures in the Longtan Formation, Guizhou Province.

The mechanical properties of coal measure rocks and their evaluation significantly impact the process and efficacy of coal measure exploration and development. This study focuses on the Guizhou Longtan Formation coal measure. The mechanical and fracturing characteristics of coal measure rock samples are analyzed via well coring, geophysical logging, and indoor experiments. Additionally, predictive models for rock mechanical parameters are developed, and an evaluation system for the Longtan Formation coal measure rock mass is established. The findings are as follows: (1) Coal measure rocks in Guizhou's Longtan Formation exhibit a relatively low elastic modulus and tensile strength, but a substantial variation in compressive strength. The triaxial compressive strength, elastic modulus, and residual strength increase nonlinearly with increasing confining pressure. As the confining pressure increases, the failure mode of the mudstone and siltstone transitions from primarily splitting failure to shearing failure. (2) Strong correlations are calculated between logging parameters and rock mechanical parameters and are used to construct three regression prediction models, yielding an average prediction accuracy of approximately 85% for rock mechanical properties. (3) Considering the rock mechanical properties, rock mass structure and stratigraphic characteristics, and the occurrence environment related to the characteristics of rock mass affecting coal measure gas development, eight evaluation indices are selected. The analytic hierarchy process-entropy weighting method is used to determine the weights of the comprehensive evaluation indices, and a coal measure rock mass evaluation system is established by utilizing gray clustering analysis. The evaluation results categorize the mudstone group (mudstone and silty mudstone) as Classes III-IV, the fine sandstone group as Classes I and II, and the siltstone group (muddy siltstone and siltstone) as Classes II and III. A comparative analysis with fuzzy comprehensive evaluation results and extenics theory evaluation results demonstrated a high level of consistency. These findings benefit coal measure rock mechanics classification and quantitative research on rock mechanics properties, providing a solid foundation for efficient coal measure gas exploration and development.

Effect of Thermoactivated Recycled Cement, Hardened Cement Powder and Hydrated Lime on the Compressive Strength of Mortars.

Thermoactivated recycled cement (RC) is a growing area of research and development in the cement industry. The approach represents a reversible process of cement hydration in which dehydrated compounds with similar characteristics to cement are obtained by means of thermal activation. To avoid CO2 emissions during the production of such RC, this study assesses the possibility of replacing ordinary Portland cement (OPC) with hardened cement powder (HCP) prepared with different proportions of hydrated lime (HL), relying on a second pozzolanic reaction, and compares it with RC mortars. Due to the thermal activation of HCP, the compressive strength increases by 11.5%. The addition of 8% HL produced an important increase in strength from 28 days to 90 days by 12.8%, although without surpassing the strength values of mortar produced only with HCP or with RC. The compressive strength results suggest the existence of a secondary pozzolanic reaction when using HCP from a cement paste source, but such a pozzolanic reaction was fully perceived in XRD patterns when using concrete as parent material, unlike cement paste, possibly due to large crystalline sand peaks that could have hindered the effective identification of smaller crystalline peaks.

Improving the acoustic performance of flexible polyurethane foam using biochar modified by (3-aminopropyl)trimethoxysilane coupling agent.

This study aims to investigate the potential of integrating natural biochar (BC) derived from eggshell waste into flexible polyurethane (FPU) foam to enhance its mechanical and acoustic performance. The study explores the impact of incorporating BC at various weight ratios (0.1, 0.3, 0.5, and 0.7wt. %) on the properties of the FPU foam. Additionally, the effects of modifying the BC with (3-aminopropyl)trimethoxysilane (APTMS) at different ratios (10, 20, and 30wt. %) and the influence of diverse particle sizes of BC on the thermal, mechanical, and acoustic characteristics of the FPU composite are investigated. The functional groups, morphology, and elemental composition of the developed FPU composites are analyzed using Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) techniques. Characteristics such as density, gel fraction, and porosity were also assessed. The results reveal that the density of FPU foam increased by 4.32% and 7.83% while the porosity decreased to 50.22% and 47.05% with the addition of 0.1 wt. % of unmodified BC and modified BC with 20wt. % APTMS, respectively, compared to unfilled FPU. Additionally, the gel fraction of the FPU matrix increases by 1.91% and 3.55% with the inclusion of 0.1 wt. % unmodified BC and modified BC with 20 wt. % APTMS, respectively. Furthermore, TGA analysis revealed that all FPU composites demonstrate improved thermal stability compared to unfilled FPU, reaching a peak value of 312.17°C for the FPU sample incorporating BC modified with 20 wt. % APTMS. Compression strength increased with 0.1wt. % untreated BC but decreased at higher concentrations. Modifying BC with 20% APTMS resulted in an 8.23% increase in compressive strength compared to unfilled FPU. Acoustic analysis showed that the addition of BC improved absorption, and modified BC enhanced absorption characteristics of FPU, reaching Class D with a 20 mm thickness. BC modified with APTMS further improved acoustic properties compared to the unfilled FPU sample (Class E), with 20% modification showing the best results. These composites present promising materials for sound absorption applications and address environmental issues related to eggshell waste.

Strengthening effect of mechanical vibration on the carbonation properties of steel slag compact

This study examines the impact of mechanical vibration on the carbonation process of steel slag, a substantial byproduct of steel production. Employing a methodical experimental design that modulates mechanical vibration frequencies, the research reveals that mechanical vibration markedly influences carbonation, with an optimal frequency of 180 Hz leading to a 27.5 % increase in compressive strength of steel slag compact and an increase in CO2 uptake of 6.8 %. The application of vibration appears to catalyze the conversion of calcium-rich minerals into well-formed rhombohedral calcite, which emerges as the predominant carbonation product. Mechanism analysis suggests that vibration-induced particle redistribution creates new reaction surfaces, thereby accelerating the carbonation process. However, the effect is more pronounced in early stages, with diminishing returns as carbonation progresses. These pivotal findings propose an innovative strategy to augment the efficiency of carbonation and the inherent material properties of steel slag, thereby fostering a more sustainable approach to the utilization of industrial byproducts.

Research on resin modified gelatin as environmental-friendly high temperature resistant wellbore stabilizer

In the development of deep shale oil and gas, the working temperature of the water-based drilling fluids is relatively high, which can cause wellbore instability due to the poor temperature resistance of the traditional environmental-friendly additives. To address this issue, this study presents a wellbore stabilizer called PMG, prepared by modifying gelatin (GT) with a resin synthesized by polyvinyl alcohol (PVA) and methacrylic acid (MA) through hydrothermal free radical polymerization, and it can withstand temperature up to 200 °C. The synthesis and thermal stability of PMG were confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The wellbore stability performance of PMG was evaluated by linear swelling test, rolling recovery test, core immersion experiment and point load test and the wellbore stability mechanism was also investigated. The results reveal that the swelling height of sodium-based bentonite (Na-BT) in 2.0 % PMG solution at 150 °C is only 0.97 mm; the hot-rolling recovery rate in 2.0 % PMG solution at 200 °C is 72 %; the artificial core still maintains its original appearance after being immersed in 2.0 % PMG solution at 200 °C for 16 h, and the compressive strength increases by 12 %, effectively strengthening the wellbore. In addition, the EC50 value of PMG is > 106 mg/L, and the BOD5/CODcr value is 31 %, indicating that it is non-toxic and biodegradable. PMG has excellent wellbore stability performance, in addition to being able to adsorb on the surface of Na-BT by electrostatic action and hydrogen bonding, the PMG micelles that precipitated from the aqueous solution due to the breaking of hydrogen bonds in the molecular chain at high temperature also form a film on the clay surface, aggregating and cementing the clay particles together, further enhancing the wellbore stability.

Injectable Dual Fenton/Enzymatically Cross-Linked Double-Network Hydrogels Based on Acrylic/Phenolic Polymers with Highly Reinforced and Tunable Mechanical Properties.

Injectable hydrogels have been extensively used as promising therapeutic scaffolds for a wide range of biomedical applications, such as tissue regeneration and drug delivery. However, their low fracture toughness and brittleness often limit their scope of application. Double-network (DN) hydrogel, which is composed of independently cross-linked rigid and ductile polymer networks, has been proposed as an alternative technique to compensate for the weak mechanical properties of hydrogels. Nevertheless, some challenges still remain, such as the complicated and time-consuming process for DN formation, and the difficulty in controlling the mechanical properties of DN hydrogels. In this study, we introduce a simple, rapid, and controllable method to prepare in situ cross-linkable injectable DN hydrogels composed of acrylamide (AAm) and 4-arm-PPO-PEO-tyramine (TTA) via dual Fenton- and enzyme-mediated reactions. By varying the concentration of Fenton's reagent, the DN hydrogels were rapidly formed with controllable gelation rate. Importantly, the DN hydrogels showed a 13-fold increase in compressive strength and a 14-fold increase in tensile strength, compared to the single network hydrogels. The mechanical properties, elasticity, and plasticity of DN hydrogels could also be modulated by simply varying the preparation conditions, including the cross-linking density and reagent concentrations. At low cross-linker concentration (<0.05 wt %), the plastic DN hydrogel stretched to over 6,500%, whereas high cross-linker concentration (≥0.05 wt %) induced fully elastic hydrogels, without hysteresis. Besides, DN hydrogels were endowed with rapid self-recovery and highly enhanced adhesion, which can be further applied to wearable devices. Moreover, human dermal fibroblasts treated with DN hydrogels retained viability, demonstrating the biocompatibility of the cross-linking system. Therefore, we expect that the dual Fenton-/enzyme-mediated cross-linkable DN hydrogels offer great potential as advanced biomaterials applied for hard tissue regeneration and replacement.

Impact of Waste Marble Powder as A Partial Alternative Material for Cement

Waste marble powder generated from the sawing and the mining activity of marble stone caused environmental problems that harmed human health. This current research aimed to investigate the influence of waste marble powder to substitute cement partially in mortar production. The mortar preparation with the mixture compositions of 0-50% marble powder was investigated for their resistance of compression and their porosity. The characterization was assessed with X-ray Fluorescence (XRF), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), Fourier Transform Infra-Red (FTIR), and X-ray Diffraction (XRD). The finding of this research revealed that a replacement by up to 10% marble powder obtained an increase in compressive strength after 28 days. A low level of marble powder to replace cement led to a less porous microstructure of the mortars. These confirmed that waste marble powder could be applied to manufacture mortars. In addition, the utilization of waste marble powder as an alternative building material would reduce the damage to the environment.

Mechanical and Structural Characterization of Resole Resin Composites Reinforced with Sabai Grass-Derived Cellulose Fibers

Cellulose fibers were extracted from Sabai grass (Eulaliopsis binata) using mechanical and chemical treatments. The grass was ground to ~250 µm powder and bleached with hydrogen peroxide and acetic acid. The bleached fibers were treated with 6% sodium hydroxide solution and incorporated into resole resin at various weight percentages to prepare the composites. The prepared samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and compressive strength tests. The XRD and FTIR showed a nanometric crystallite size of 3.84 nm and effective removal of non-cellulosic compounds, respectively, leading to a compressive strength increase from 15.60 MPa to 25.26 MPa at 3 wt.-% cellulose fiber. The compressive strength improved up to 3 wt.-% cellulose fiber, which however declined upon adding more filler. SEM revealed modified surface morphology in the composites with cellulose fibers.

THE EFFECT OF POLYPROPYLENE FIBERS ON COMPRESSIVE AND SPLIT TENSILE STRENGTH OF LIGHTWEIGHT CONCRETE

This study was carried out to design lightweight concrete, which is enriched with polypropylene fibers using coarse pumice and sand fine aggregates. Lightweight concrete specimens were classified into distinct groups based on fibers content employed, namely a control group with 0 kg/m³ and the experimental incorporating 0.1 kg/m³, 0.3 kg/m³, 0.5 kg/m³, and 0.7 kg/m³ varying quantities of polypropylene fibers. Subsequently, after a curing period of 28 days, the hardened concrete test was conducted on cylinder specimens measuring 150 mm x 300 mm. The consistency of the fresh concrete mixture was tested using the Abrams cone test, which revealed a decrease in the workability of fibers-reinforced concrete with an increase in fibers volume in the mixture. The test aimed to determine the effect of polypropylene fibers on compressive and tensile strength of lightweight concrete. The optimal compressive and split tensile strength was observed at fibers volume fraction of 0.5, to obtain 7.84 MPa, or 56.68% increase in compressive strength, and 2.12 MPa or 42.86% rise in tensile strength. Based on compressive and split tensile strength obtained from this study, concrete was classified as highly lightweight structural concrete, which served as an insulator.

Reducing carbonation degradation and enabling CO2 sequestration in alkali-activated slag using cellulose nanofibers

This study evaluated the role of cellulose nanofibers (CNF) in reducing the carbonation degradation of alkali-activated slag (AAS) samples. AAS samples prepared with different dosages of CNF (0 %, 0.10 %, and 0.80 % by weight of the binder) were exposed to natural and accelerated carbonation for up to 90 days. The effects of carbonation on the microstructure of AAS paste samples were monitored using FTIR, XRD, TGA, MIP, and BSE/SEM. It was observed that after 90 days of natural carbonation, the control batch exhibited a reduction in compressive strength, whereas the CNF batches showed an enhancement. Notably, the CNF-containing batches maintained consistent strength over time, with no reduction in strength. Similarly, after 90 days of accelerated carbonation, CNF 0.10 % and CNF 0.80 % showed an increase in compressive strength compared to the control batch. Despite this enhancement in compressive strength, microstructural studies indicated that the addition of CNF increased the extent of carbonation, leading to a higher amount of CaCO3 formation and C–S–H/C-A-S-H decalcification compared to the control batch. The beneficial effects of CNF on the strength despite increased C–A–S–H decalcification are attributed to their reinforcing effects and the ability to form composites with CaCO3.

Insights into morphology and mechanical properties of architected interpenetrating aluminum-alumina composites

Additive manufacturing (AM) technologies are unleashing the restrictions imposed by conventional manufacturing, allowing the production of innovative designs tailored to improve properties or performance. AM techniques in ceramic production allow the application of novel designs to ceramic parts, opening new opportunities for combining technologies aiming to obtain architected interpenetrating phase composites (IPCs). In this study, alumina structures with different architectures and Computer Aided Design (CAD) structure porosity oriented unidirectionally or bidirectionally, were fabricated by vat photopolymerization technique, namely Digital Light Processing. Afterwards, these structures were infiltrated with an aluminum alloy through investment casting, thus obtaining aluminum-alumina IPCs. Under compression, the IPCs presented a ductile behavior, conversely to the fragile ceramic counterparts. The IPCs compressive strength and absorbed energy were expressively higher than their ceramic counterparts. Comparing the bidirectional IPCs with the unidirectional ones, a significant increase in compressive strength and absorbed energy was observed, from 36.2% to 42.3% and from 164.8% to 358.1%, respectively, due to the greater amount and interconnection of the metal inside the ceramic structure. This study demonstrates the feasibility of this manufacturing route, combining two distinctive technologies, for the fabrication of metal-ceramic architected IPCs, allowing to tailor their mechanical properties and energy absorption capacity for a given application.

Development of eco-efficient limestone calcined clay cement (LC3) mortars by a multi-step experimental design

Calcined clays and calcium carbonates can be used to reduce clinker factor in blended cements, offering significant economic and environmental benefits. Limestone calcined clay cements (LC3) combine them as supplementary cementitious materials (SCMs) for delivering a sustainable alternative to conventional Ordinary Portland Cement products, with envisioned applications in construction and rehabilitation of historical buildings.This study reports a chemometric approach to the development of LC3 mortars, targeting to minimize clinker content while maintaining or improving the technical characteristics. To evaluate their performance, apparent density, modulus of elasticity, open porosity, water absorption, flexural and compressive strength have been considered as responses. Multiple Linear Regression (MLR) and Principal Component Analysis (PCA) were employed in a three-step mixture-process design allowing to obtain LC3 mixtures with a 21 wt% reduction in clinker while achieving notable enhancements in the physical properties (open porosity −9% and water absorption −10 %), along with commendable increases in compressive strength (+17 %) when compared to benchmark mortars produced without SCMs. The successful integration of multivariate techniques in designing sustainable building materials is showcased, highlighting the potential of chemometric methodologies to reduce the environmental impact as well as to increase the performance of building materials.

Incorporation of High Volume Ground Granulated Slag From Blast Furnaces in Pavement Quality Concrete

Supplementary cementitious materials (SCMs) are commonly introduced into the concrete mix to increase their properties, addressing the current need for durable and robust pavements. With every ton of Ordinary Portland Cement (OPC) produced through processes such as fossil fuel combustion and limestone fermentation, carbon dioxide is released into the atmosphere. Conversely, Ground Granulated Blast-furnace Slag (GGBS), being abundantly available, presents a viable more environmentally friendly alternative to cement for various concrete applications. This work studies the influence of GGBS, in combination with chemical admixtures, on M40 grade binary blended concrete mixtures. The aim of the study was to improve the strength characteristics at various stages of concrete curing. The results indicated that the GGBS-incorporated concretes (replacing 60%, 65%, and 70% of the cement) exhibited an increase in compressive strength after prolonged curing. The average density of fresh concrete mixes containing GGBS did not exhibited a noticeable increase. A marginal disparity in air content was observed in the replacement mix. Minimal length changes were observed in the drying shrinkage test after a curing duration of 360 days compared to conventional concrete mixtures.

Prediction of mechanical properties of high strength steel fibre reinforced concrete using linear regression techniques

In this study, researchers investigated the mechanical properties of high-strength steel fiber-reinforced concrete (HSFRC). The experimental study involved evaluating high strength concrete (HSC) using various steel fibre contents (ranging from 0.25% to 2.00%) and different water-cement ratios (WCR) (0.25, 0.30, 0.35, and 0.40). Adding 1.50% steel fibre to HSC led to an increase in compressive strength (CS). Specifically, the CS improved by 13.42% to 15.19% for WCR of 0.25, 0.30, 0.35, and 0.40. Including 1.50% steel fibre enhances split tensile strength (STS). The STS increased by 25.89% to 32.62% for the same WCR. High-strength concrete with 1.50% steel fiber exhibited improved flexural strength (FS). The FS rose 29.00% to 35.07% for the specified water-cement ratios. The study also considered the modulus of elasticity (ME) at 28 days. Interestingly, the strength of HSC decreased as the WCR increased. Lower WCR generally contributed to better mechanical properties. The experimental results were compared with linear regression analysis and existing empirical formulas. The regression analysis demonstrated good agreement with the experimental findings. Overall, the optimal steel fibre content was 1.50% across all WCR, significantly improving mechanical properties. The study provides valuable insights for designing HSC with enhanced performance.

Bio-Electrokinetic Improvement of Deltaic Soil

In addressing problematic soils, geotechnical engineers employ two key strategies: compatibility and improvement. This study focuses on soft and CL deltaic sediments, and seeks to enhance cementation by investigating microbially-induced calcium carbonate precipitation (MICP). Sporosarcina pasteurii bacteria, together with a cementation solution (urea and calcium-containing salt), were electrokinetically injected into deltaic clay soil from the Telar River in Iran. The initial samples, with a dry unit weight (γd) of 12.75 kN/m³, underwent injections in two modes: simultaneous injection of the bacterial and cementation solutions and individual injection in a sequential order. Unconfined compression strength tests and laboratory vane shear tests were conducted to assess changes in soil strength parameters, while a consolidation test was performed to investigate alterations in soil settlement parameters. A comparative analysis with an electroosmosis control sample revealed a remarkable increase in compressive strength and undrained shear strength for MICP bio-electrokinetic improvement. Moreover, the consolidation test demonstrated that the compression index (Cc) and recompression index (Cr) exhibited a more pronounced decline in the simultaneous injection than individual injection. This highlights the dual impact of the bio-electrokinetic method, namely the enhancement of shear strength and the mitigation of settlement in deltaic clay soil. The calcium carbonate content was measured for the samples, and the results indicated a higher degree of participation for the samples subjected to simultaneous injection. Microstructure analyses were conducted on samples, and calcite and vaterite were observed in bio-cemented samples.

Enhancing mechanical properties of Al-Zn-Mg-Cu alloys: The impact of high strain rate compression and subsequent heat treatment on microstructural evolution

This study presents a comprehensive examination of the Al-Zn-Mg-Cu alloy, focusing on the effects of high strain rate dynamic compression and heat treatment on its performance. The research aimed to understand the underlying microstructural mechanisms contributing to the enhanced mechanical properties of the alloy, which is critical for applications in aerospace and automotive industries. High strain rate dynamic compression tests, conducted at 3.0 × 1000 s−1, revealed a significant increase in both yield strength and ultimate compression strength of the Al alloy, which was accompanied by a increase in hardness. Post-compression microstructural analyses utilizing transmission electron microscopy and scanning- transmission electron microscopy indicated that significant changes occurred during testing. Key findings include the development of micro shear bands, alterations in the size and distribution of precipitates, and the emergence of new plate-like precipitate formations. Subsequent T6 heat treatment led to further microstructural evolution, particularly impacting the volume fraction and size of η' precipitates. The study highlights the crucial role of dislocation-precipitate interactions, where dislocations are effectively pinned by precipitates, thereby contributing significantly to the material's strength. These results demonstrate the potential of high strain rate dynamic compression coupled with heat treatment as a method to significantly enhance the mechanical properties of Al-Zn-Mg-Cu alloys. Overall, the findings provide valuable insights into the optimization of this alloy for high-performance applications, emphasizing the importance of controlled microstructural engineering.

An experimental investigation on mechanical characteristics of steel-fiber-reinforced volcanic concrete

Raw materials of concrete are one of the main pollution resources. Sustainable concrete is one of the significant solutions that can be used to reduce carbon emission. This study aims to use volcanic ash (VA) as a supplementary cementitious material (SCM) for producing sustainable concrete. The effects of VA on the properties of steel fiber reinforced concrete (SFRC) are evaluated. The fresh and hardened concrete's characteristics of steel fiber volcanic ash concrete (SFVC) is presented and assessed. Slump test, compressive strength, splitting tensile tests, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Fourier transform infrared (FTIR) spectrophotometry are used to investigate the effect of VA concrete performance. Five groups of SFVC were prepared using sixteen different mixes; 0 %, 2.5 %, 5.0 %, and 7.5 % of VA were used as a partial replacement of cement with 0, 0.5,1.0 %, and 1.5 % of steel fiber (SF). The findings demonstrated that concrete sustainability could be improved by employing VA as a partial replacement for cement, resulting in improved mechanical performance with a slight reduction in workability. The optimum mechanical and microstructure properties of SFVC were achieved with the incorporation of 5 % VA instead of cement with 1 % steel fiber, at age 28 days. The increase in compressive strength and tensile strength up to 25 % and 31 %, respectively. The employing of VA as a SCMs material resulted in better ITZ between aggregate and cement mortar and exhibited a dense surface with less pores compared to control mix.