Increase In Compressive Strength Research Articles

Use of lignocellulose-degrading enzyme bio-cemented soils in the construction industry

In their activity, termites break down biomass into glucose, forming cementitious compounds. This results in rainfall-resistant mounds for their shelters, which interests the construction industry. This study explored the potential application of the abundant naturally bio-cemented termite mound soils in highway construction. Experimental investigations compared these mound soils to surrounding soils, revealing that mound soils are 68.2% finer in particle size distribution and have 81.4% lower organic content. Atterberg limits indicated 14.6% higher plasticity and a 5.3% increase in specific gravity for mound soils. Atomic Absorption Spectroscopy (AAS) showed no significant difference in chemical composition. Proctor tests indicated that the compaction characteristics of the soils were comparable, confirming their engineering viability without modifications. Mound soils exhibited a twofold increase in Unconfined Compressive Strength (UCS) and a 33.9% increment in California Bearing Ratio (CBR) strength. One-way ANOVA tests confirmed these differences with p-value ranges of 0.0056-0.0361 below the 0.05 significance threshold. The study advocates utilising eco-friendly naturally bio-cemented mound soils in highway construction, meeting minimum standards. Mound soils from one acre can construct up to 2,500m highway, optimising resource use, promoting sustainability by repurposing natural materials, and significantly reducing carbon emissions. Further research on soil improvement using lignocellulose-degrading enzymes is recommended.

Rubber-lignin-ammonium polyphosphate bio-composite foams: Fabrication, thermomechanical properties and flame retardancy

Bio-composite foams based on Epoxidized Natural Rubber (ENR) filled with lignin (LG) and ammonium polyphosphate (APP) were fabricated via batch foaming. The addition of APP accelerated the foaming process at lower temperatures. Pre-mixing induced ionic and hydrogen bonding between the LG and the APP particles, which reduced crosslinking between LG and ENR. The resulting ENR bio-composite foams with LG/APP exhibited a significant increase in compressive strength (up to 700 %) and modulus (up to 600 %) compared to the ENR foam baseline. Furthermore, the LG/APP foams demonstrated lower thermal conductivity than both the ENR foam baseline and foams containing only LG or APP, attributed to optimal thermal conduction in the solid phase and convection within the pore cells. The combination of APP and LG produced synergistic effects, with phosphorus (from APP) and high carbon content (from LG) enhancing flame-retardant efficiency. This study highlights the potential of these sustainable bio-composite foams for applications requiring enhanced thermal insulation and flame retardancy attributes for insulation and other practical applications.

Applicability of few layer graphene derived from annoni grass biomass on the mechanical properties of cement mortars

In this work, we report the potential applicability of few layer graphene (FLG) synthesized from annoni grass (AG) biomass (Eragrostis plana Nees) by investigating its impact on the flexural and compression strength of cement mortars. For this purpose the AG biomass was collected and burnt at the temperature of 400 °C per 60 min, obtaining the AG ash (AGA). For FLG production, the AGA was mixture with the chemical reagent potassium hydroxide (KOH) and burnt at the temperature and time of 850 °C and 60 min, respectively. For the mechanical properties analysis, a reference sample (A0-without FLG) and samples with different percentage of FLG were prepared, specifically 0.02 % (A1), 0.03 % (A2), 0.05 % (A3), 0.07 % (A4) and 0.1 % (A5). Statistical analysis (Analysis of Variance, ANOVA) of the mechanical properties demonstrates a maximum flexural and compression strength in sample A2. The flexural and compression strength increase 25.2 % and 10.1 % compared to the reference mortar. These results indicate that the FLG produced from AG not only improves the mechanical properties of mortars but also presents significant environmental benefits, because AG is considered an invasive pest of agricultural fields of the southern region of Brazil. Therefore, with its removal from the fields it would be contributing to environmental preservation.

Power ultrasound-assisted enhancement of granulated blast furnace slag reactivity in cement paste

The impact of the power ultrasound (PUS)-assisted preparation technique on the physicochemical and mechanical characteristics of cement-granulated blast furnace slag (GBFS) pastes was studied. Pastes containing GFBS with varying particle size fractions, partially replacing Portland cement, were tested using PUS in pulse mode in a sonoreactor with closed-circuit cooling. The best-performing cement-GBFS composite paste showed a notable increase in compressive and flexural 2-day strengths (132% and 58%, respectively), as well as Vickers hardness and modulus of elasticity (98% and 74%, respectively) when compared to conventional mixing procedures. Similarly, the BET surface area increased by about 111%, cumulative heat release increased by about 34% after 2 days, reduced substitute setting times (initial by about 32%, final by about 55%), and portlandite content decreased by about 29%. The power of this association is linked to C-S-H/C-A-S-H nucleation seeding, which can be formed via an interfacial mediator induced by PUS.

Study of the Structure and Properties of Concrete Modified with Nanofibrils and Nanospheres

The application of modifying nanoadditives in the technology of cement composites is currently a relevant and widely researched topic in global materials science. The purpose of this study was to investigate new nanoadditives—nanofibrils made from synthesized wollastonite (NF) and nanospheres from corundum (NS)—produced by LLC NPK Nanosystems (Rostov-on-Don, Russia) as a modifying additive. During the experimental investigations, the mechanical properties of cement pastes and concrete were examined. This included an analysis of the density, compressive and bending strength, as well as water absorption of concrete that had been modified with NF and NS additives. X-ray phase and microstructural analyses of concrete were performed. It was established that modification of cement composites with NF and NS additives had a beneficial effect on their properties, and the optimal amount for both types of additives was 0.3% by binder weight. The highest recorded enhancements in compressive and flexural strength of concrete with 0.3% NF were 7.22% and 7.04%, respectively, accompanied by a decrease in water absorption by 4.70%. When modifying concrete with 0.3% NS, the increases in compressive and flexural strength were 2.71% and 2.48%, and water absorption decreased by 1.96%. Modification of concrete with NF and NS additives did not have a significant effect on the change in concrete density, which was no more than 1%. Based on the results of phase analysis, it was established that concrete with NF and NS additives were characterized by the presence of five main phases: quartz, portlandite, calcite, larnite, and olivine-Ca. It was found that compositions with 0.3% NF and NS differed from the control composition by the presence of such a phase as olivine-Ca. Microstructural analysis confirmed the effectiveness of NF and NS additives. The microstructure of the modified concretes was distinguished by the extensive occurrence of clusters composed of calcium silicate hydrate zones. The conducted studies prove the possibility of using NF and NS as modifying nanoadditives in the technology of cement composites. The addition of nanofibrils from synthesized wollastonite is the most effective and promising and is recommended for use in real construction practice.

Potential for material valorization of composites (glass fiber in polyester resin) in concrete: performance evaluation on mortar

IntroductionGlass fibers with polyester resin structural composites are highly sought after in many sectors such as transportation industries, thanks to their low density and fairly good mechanical properties. However, their end-of-life management is not yet satisfactory. Composites mostly end in energy recovery in the best-case scenario or, worse, in landfills. Transformation into shreds and powders for reuse as a new source of raw material for the construction sector (concrete) is an economically and environmentally attractive recovery solution. The present study investigates the development of a concrete filled with glass/polyester composite shreds.MethodsTo this end, rheological (cone spread) and physico-mechanical (density and mechanical strength in flexion and compression) characterization tests were carried out. Several mix designs were tested in order to understand the impact of introducing composite shreds as a substitute for sand. Composite shreds were introduced in the following ratios by volume: 0, 1, 1.5, 2, 2.5, 3, and 7% with water and cement ratio equal to 0.5, 0.6, and 0.7.Results and discussionThe results obtained indicate that workability decreases with the substitution of sand by shreds. For a substitution of sand by shreds of 2%, it is relatively small, and the pouring of the mortar is still feasible. The decrease can be attributed to the water absorption of the composite shreds. Concerning mechanical results, for formulations with a substitution percentage of composite shreds lower than 3%, the mechanical strength (both compression test and flexure test) is slightly higher than that of the reference sample. The increase in compressive strength that can be observed is at its maximum, equal to 10%, compared to that of the reference sample. These results are in line with density results, which are also slightly higher than that of the reference sample. This effect can be attributed to water absorption of composite shreds and the filling effect of the powders. For a percentage of substitution equal to 7%, the mechanical strength is lower than that of the reference sample (30% decrease), with a compressive strength equal to 33 MPa (47 MPa for the reference sample). For this percentage of substitution equal to 7%, a decrease in density is also observed (6% decrease) and can be explained by the porosity created by the incorporation of the composite shreds into the mortar.

Clayey soil stabilisation with geopolymerized olivine and glass fibers

In some engineering applications soil stiffness only could not be a reliable parameter in accordance with specific standardizations especially when dealing with dynamic loading. In other words, foundation soil should be altered regarding its ductility in order to prevent sudden damage due to brittleness. Plenty of researchers were concerned to focus on soil reinforcement using glass fibers. Besides, the alkaline activation method has been adapted to alter the strength properties of soft soil. Furthermore, recent alkaline activation of soft soil, using olivine and Potassium hydroxide, coupled with soil reinforcement was adapted to change the post-peak behavior of soft soil. The aim was towards ultimate strength increase and enhancement of failure mode. In this research, geopolymerized soil and geopolymerized reinforced soil were cured for 7, 28, 90 and 180 days respectively. Compressive stress tests were conducted on both mixtures namely SO and SOG samples. Results drawn from the tests revealed a drastic increase in compressive strength for SO samples cured for 28 and 90 days, namely 3,64 MPa and 7,5 MPa respectively. Though a sharp drop was seen when approaching failure. With the addition of reinforcing glass fibers for the suggested curing regimes the failure mode was enhanced to become more ductile.

Bacterial cellulose-graphene oxide composite membranes with enhanced fouling resistance for bio-effluents management

Bacterial cellulose composites hold promise as renewable bioinspired materials for industrial and environmental applications. However, their use as free-standing water filtration membranes is hindered by low compressive strength, fouling, and poor contaminant selectivity. This study investigates the potential of bacterial cellulose-graphene oxide composites membranes for fouling resistance in pressure-driven filtration. Graphene oxide dispersed in poly(ethylene glycol) (PEG-400) is incorporated as a reinforcing filler into 3D network of bacterial cellulose using an in-situ synthesis method. The effect of graphene oxide on in situ fermentation yield and the formation of percolated-network in the composites shows that the optimal membrane properties are reached at a graphene oxide loading of 2 mg/mL. The two-dimensional graphene oxide nanosheets uniformly dispersed into the matrix of bacterial cellulose nanofibers via hydrogen-bonded interactions demonstrated nearly twofold higher water flux (380 L m−2 h−1) with a molecular weight cut-off ranging between 100–200 KDa and a sixfold increase in wet compression strength than pristine BC. When exposed to synthetic organic foulants and bacterial rich feed solutions, the composite membranes showed more than 95% flux recovery. Additionally, the membranes achieved over 95% rejection of synthetic natural organic matter and bacterial rich solutions, showcasing their enhanced fouling resistance and selectivity.

Experimental study on recycling rubber to increase the impact resistance of cement mortar

The COVID-19 pandemic has led to a surge in medical waste generation, posing hazards to both the environment and global health. The impacts of the COVID-19 pandemic’s medical waste hazard may persist long after the pandemic itself subsides. Improper disposal of medical waste can contaminate environment, posing risks to ecosystems and public health. Discarded medical rubber gloves, for example, can become a source of infection, improper disposal of these gloves can escalate the spread of infectious diseases and increase the risk of transmission of the virus to the general public. This study proposes an innovative and sustainable method to reinforce cement mortar by adding recycled glove rubber as an additive to cement mortar to increase its resistance to impact loads. This study conducted uniaxial compression tests, separating hopkinson pressure bar (SHPB) experiments and SEM observations to evaluate the quasi-static compressive strength and dynamic stress of recycled rubber fiber mortar (RRFM) with varying recycled rubber fiber (RRF) contents (0, 1%, 2%, 3%). Strain curves, dynamic increase factor (DIF), energy absorption rules, failure modes, and microstructure of RRFM mixtures. The experimental results demonstrate that with the addition of RRF, the dynamic stress-strain curve flattens and the peak strain gradually increases. The RRFM sample shows stronger toughness. In comparison to regular cement mortar (NM), RRFM has a higher DIF and specific absorbed energy, a faster increase in dynamic compressive strength, and the ability to absorb more energy per unit volume. Under the same impact load, RRFM has fewer and smaller cracks than NM. Scanning electron microscopy (SEM) testing also observed that RRF formed a strong connection pattern with the cement mortar matrix.

Study on the effect of cinder ash as an auxiliary additive mineral in hydrated lime treatment for expansive sub-grade soil in road construction

Expansive soils pose significant challenges to road construction globally due to their tendency to expand and contract with changes in moisture content, leading to pavement failure. In the construction industry, finding an economical and cost-effective alternative to conventional road construction materials is crucial. The use of a natural cinder ash and hydrated lime mixture as reinforcement has proven to be effective in addressing this issue. Cinder ash, a readily available waste material in countries like Ethiopia, is adaptable and water-resistant, making it an ideal choice for reinforcing expansive soil. This article investigates the strength performance of a cinder ash and hydrated lime mixture as a reinforcement material for expansive soil. The study involves mixing 0%, 20%, 25%, 30%, and 35% of cinder ash with soil stabilized with 2–5% hydrated lime. Expansive soil samples are prepared according to the ASSHTO & ASTM method and tested for compressive strength, California bearing ratio, bulk density, and water absorption. The findings reveal a 448.62%, and 374% increase in compressive strength and California Bearing Ratio respectively for the specimen containing 5% hydrated lime and 35% cinder ash, cured for 28 days. The water absorption is minimized at 15.23% for the 5% hydrated lime and 35% cinder ash mixture; while the maximum density of the soil is observed at 1.774 kg/m3 for the optimal combination of 5% hydrated lime and 35% cinder ash mix. The study suggests that using 5% hydrated lime and 35% cinder ash content for the stabilization of expansive soil significantly enhances the strength characteristics of compressed stabilized soil.

An environmental approach to cement admixtures: Utilization of waste olive seed powder as a bio-polymeric admixture.

The integration of organic wastes into cement-based materials shows promise as a solution to mitigate environmental pollutants. It achieves this by minimizing waste sent to landfills and in some conditions decreasing Portland cement use. One of these organic wastes that produces positive effects when used in cement products is olive seed. In this study, the effect of a new generation bio-polymeric admixture on the physical and mechanical properties of cement mortars is examined in detail. The bio-polymeric admixture is prepared by grinding olive seeds in 0/125μm sizes. The olive seeds have been used as bio-polymeric admixture in cement mortars at different rates, i.e., 0, 0.2, 0.35, 0.5, 1 and 1.5% of total weight. The olive seed is characterized by XRD, FT-IR analysis and by determining extracts, pectin, cellulose, hemicellulose and lignin content. The characteristics of hydration products were analyzed by SEM/EDS and XRD investigations. Effect of bio-polymeric admixture addition on the unit weight, flowability, setting time, compressive and flexural strength and capillary water absorption was analyzed. The results suggested that the bio-polymeric admixture hindered the cement hydration at low usage rates but promoted at high usage rates. Accordingly, 28days compressive and flexural strength of test samples decreased. However, 1.5 wt% bio-polymeric admixture was associated with a slight increase of 150-days compressive strength. Bio-polymeric admixture improves the hydrophobicity property of the hardened mortar samples by declining effect on the water absorption. Another important effect of the bio-polymeric admixture contribution was also observed on the flowability property of the cement mortars. As the bio-polymeric admixture increased, the flow diameter values of the mortar were also significantly increased. The research outcomes suggested for the first time the beneficial effect of bio-polymeric admixture as a natural and bio-degradable alternative of chemical admixtures on especially flowability, set retarder and hydrophobicity of cement mortars with comparable mechanical properties.

Use of metakaolins from Eseka and Dibamba‐Cameroon as an optimization additive of CEM I Portland cement mortar

AbstractThe present study deals with two kaolins from Eseka and Dibamba‐Cameroon to determine their potential suitability as additive of CEM I 42.5R and to optimize the properties of cement in the sense to promote low‐carbon cement. X‐ray diffractometry was used to establish the mineralogical composition of two kaolins. X‐ray fluorescence was carried out to determine the chemical composition of kaolins and cement. Fine metakaolin powders obtained at 700°C were used as additive in CEM I 42.5R. Furthermore, consistency, setting time, water absorption, compressive and flexural test, and shrinkage test were evaluated. Scanning electron microscopy analysis was carried out to evaluate the microstructure variation. The substitution of CEM I with metakaolin resulted in a considerable increase in compressive and flexural strength from days 7 to 28 at optimum value. The compressive and flexural strengths at 28 days at optimum value of metakaolin increase to 52% and 44%, respectively, explaining the equilibrium oxides in the cement. The maximum values of strength with 20 wt.% MK1 and 30 wt.% MK2 at 7, 14, and 28 days appear in both cases when the ratio of SiO2/Al2O3 is between 2.8 and 2.9. The silica modulus and alumina modulus of cement–metakaolin improved when metakaolin was added. The properties of cement were optimized with a 52% increase in compressive strength at 28 days.

Assessment of impact load effect on self-sensing of cement composites incorporating hybrid silicon carbide-graphite under various environmental conditions

This study investigates the self-sensing abilities of hybrid silicon carbide-graphite cement composites (HSCGC) under various environmental conditions, focusing on dynamic impacts. Integrating silicon carbide (SiC) and graphite enhances the mechanical and electrical properties of these composites. Tests showed that composites with 30 % SiC and 2 % graphite had a 14.1 % increase in compressive strength and up to 85 % decrease in electrical resistivity. Water absorption reduced by 3.25 %, indicating better durability. Impact resistance ratios (IRR) varied with humidity and impact angles, with the highest IRR observed at 70 % humidity and a 30-degree angle. Self-sensing responses indicated that higher SiC and graphite content maintained stable conductivity, especially at 60 and 90-degree angles. Temperature changes affected resistivity, negligible at −10°C and increased at 45°C. The study concludes that HSCGCs are suitable for smart construction materials, capable of real-time environmental and structural monitoring, advancing predictive models and control systems.

Synthesis of La2Ti2O7 nanoscale powder and ceramics based on it by sol-gel and spark plasma sintering

The application of ceramics as matrices for the immobilization of radionuclides for the purpose of their safe long-term disposal or beneficial use is being studied with an emphasis on phase stability, structural integrity, hydrolytic stability, etc. In this work, a combined approach was investigated, based on the sol-gel citrate synthesis of nanosized La2Ti2O7 powder and its subsequent spark plasma sintering to produce dense ceramics. The phase composition and structure of the nanosized La2Ti2O7 powder and ceramic samples based on it, obtained in the temperature range of 900–1300 °C, were studied by XRD and SEM. It has been shown that the powder synthesis conditions ensure the formation of nanosized crystalline La2Ti2O7 grains, whose consolidation under spark plasma heating conditions proceeds with a change in the phase composition from single-phase La2Ti2O7 of monoclinic structure to orthorhombic with an admixture of LaTiO3 at temperatures above 1200 °C. It was revealed that the change in the ceramic structure is accompanied by the formation of non-porous and defect-free monolithic samples. It was determined that such a change leads to an increase in relative density (81.3–95.7%) and compressive strength (78–566 MPa) of the ceramic samples. However, the hydrolytic stability of the ceramics decreases, as indicated by an increase in the leaching rate of La3+ from 10–7 to 10–5 g/cm2·day. The obtained results are useful for the systematic study of materials suitable for immobilization technologies of radioactive waste in ceramics.

Understanding the impact of nickel coating on the mechanical and corrosion behaviour of copper foams

ABSTRACT This study used a sponge replication technique to fabricate open-cell copper (Cu) foams with varying pore sizes. Nickel coating was applied via electrolysis to produce nickel-copper (NiCu) foams to enhance the Cu foams' energy absorption efficiency and corrosion resistance. The foams were characterized under static conditions to assess their compressive and corrosion properties. The nickel coating improved compressive strength by increasing foam strut thickness and reducing defects, as observed via scanning electron microscopy (SEM). The 10 Pores per inch (PPI) NiCu foam shows a substantial increase in compressive strength, close to 17.7%, compared to the 10 PPI Cu foam, resulting in a maximum compressive strength of 11.3 MPa. Similarly, 20PPI NiCu foam shows an increase of compressive strength of 20% when compared to 20 PPI Cu foam. NiCu foams significantly reduced corrosion current density compared to uncoated Cu foams, indicating enhanced corrosion protection from the nickel coating.

Experimental Investigation on the Properties of Concrete Containing Waste HDPE Plastic and Copper Slag as Coarse and Fine Aggregates Replacement

Resource concerns have become apparent globally, particularly in the construction sector due to the exploitation of resources for developing globalized infrastructures. This has led to challenges, especially in sourcing construction materials. Consequently, numerous studies have focused on waste management strategies with eco-efficient parameters, particularly in the realm of construction aggregates. While previous research has explored alternatives for these aggregates, there remains ample opportunity for further investigation on the effectiveness and potential of alternative materials in construction projects to promote sustainable resource management. The research aims to fill this gap by examining the impact of using alternatives for both fine and coarse aggregates, specifically copper slag and waste HDPE. This study investigates the effects of partially incorporating waste HDPE plastic and Copper slag on the strength and sustainability of concrete, with the goal of evaluating their viability as sustainable alternatives in construction materials in the construction sector. Three percentages of High-Density Polyethylene (HDPE) Plastic (10%, 20%, and 30%) and Two Percentages (30% and 40 %) of copper slag were incorporated with the weight of Coarse aggregate and Fine aggregate respectively. Comparisons of conventional concrete with concrete incorporating HDPE waste & copper slag as coarse aggregate and fine aggregates were conducted. From investigation it was found that concrete incorporating 10% of HDPE and 40% of copper slag cured for 7 and 28 days had 10% increase in compressive strength compared to the nominal mix and flexural strength 25% and 40% more than nominal mix. The concrete incorporating 10% of HDPE and 30% of copper slag had 18% reduction in split tensile strength for cylinders cured for 7 days and 55% increase in split tensile strength for cylinders cured for 28 days.

Stress-Strain Behavior of Soft Soil Stabilized with Nickel Slag, Limestone, and Aluminum Hydroxide

Soil stabilization by combining several minerals is a form of material engineering aimed at increasing the bearing capacity of the soil to a higher level. The development of waste-based materials and the utilization of local potential are part of environmentally conscious construction. This study aims to analyses the mechanical behaviour of soil stabilized with several pozzolanic materials derived from nickel processing waste and limestone, which are local materials with very large deposits. ASTM standards were used in this study for both physical and mechanical testing. Unconfined compressive strength (UCS) tests were conducted to compare the mechanical behaviour of stabilized soil with that of natural soil. The test samples used were cylindrical with a diameter of 35 mm and a height of 70 mm. The binding materials consisted of nickel slag, aluminium hydroxide, and limestone, with the amount of each material based on the dry soil weight (γdry). The addition of lime in this study was varied at 2%, 4%, and 6%. The test results generally show that lime variations and curing time affect the increase in unconfined compressive strength (qu), with the highest value of 30.91 kg/cm² observed at 6% lime content after 28 days of curing.

Eco-Friendly Concrete with Improved Properties and Structure, Modified with Banana Leaf Ash

The reduction of carbon footprint, the recycling of agricultural waste, and the development of novel environmentally friendly building materials are urgent matters that necessitate innovative solutions. The objective of this study is to explore the feasibility of utilizing banana leaf ash (BLA) as a partial substitute for cement in conventional density concrete technology. The BLA-modifying additive was produced under laboratory conditions. Its chemical, phase and granulometric composition was assessed. To determine the degree of effectiveness of BLA, eight concrete compositions were developed, where the BLA content varied from 0% to 14% with an interval of 2%. The properties of fresh concrete, such as density and slump, as well as compressive strength, flexural strength, water absorption, and microstructure of hardened concrete, were studied. It has been determined that the BLA additive exhibits pozzolanic activity, with a SiO2 content of 50.83%. It is recommended that the replacement of cement with BLA does not exceed 10% for optimal results. Concrete modified with 6% BLA had the best properties and structure. The study revealed a significant 7.42% increase in compressive strength, a 7.01% increase in flexural strength, and a notable 9.28% decrease in water absorption. Thus, the obtained result proves the possibility of using BLA as a modifying additive in the technology of cement composites. The developed concrete has improved properties and is a more environmentally friendly building material than conventional concrete.

Physical and Mechanical Properties of Autoclaved Aerated Concrete (AAC) with Ceramic and Gypsum Waste (CGW) Addition Before and After Exposure to Direct Fire at Temperatures up to 920°C

This research endeavors to comprehensively explore the physical and mechanical properties of Autoclaved Aerated Concrete (AAC) with ceramic and gypsum waste (CGW) addition before and after exposure to direct fire at temperatures up to 920°C. The investigation focuses on determining the effects of CGW addition on AAC properties before and after exposure to direct fire at temperatures reaching 920℃ for 300 seconds. The main objective of this research was to determine the work density and compressive strength of AAC-CGW on the surface of direct fire exposure. In pursuit of this goal, various compositions of AAC with CGW, ranging from 5% to 30% wt/wt, were accurately prepared. The physical and mechanical were conducted before and after subjecting to direct fire testing. Important parameters such as work density, ranging from 593.71kg/m3 to 672.70kg/m3, and compressive strength from 1.64MPa to 2.39MPa, were analyzed. The findings demonstrated that the compressive strength exhibited an increase with CGW addition, particularly within the 5% wt/wt. The high point compressive strength value recorded was 2.39MPa for a 5% wt/wt CGW addition, reflecting a 45.73% increase in compressive strength compared to the reference sample (RS). The study also revealed convincing fire resistance results. Indicating for the reference sample (RS), the samples exhibited surfaces devoid of cracks, burns, or melting during direct fire exposure exceeding 920℃ for 300 seconds. Furthermore, CGW addition contributed to a remarkable 20.1% improvement in thermal insulation compared to the RS. Direct fire resistance testing had a positive influence on the physical and mechanical characteristics of AAC-CGW samples. The average work density experienced a 9.9% reduction, while compressive strength exhibited an 18.8% increase. Direct fire exposure led to an outstanding 53.30% enhancement in compressive strength compared to the sample.

Performance evaluation of high-performance concrete mixes incorporating recycled steel scale waste as fine aggregates

In this study, steel-scale waste (SSW), a byproduct generated during the manufacturing of steel, was investigated as a potential alternative to natural fine aggregates (sand) for preparing high-performance concrete (HPC). Three grades of sand and SSW with different particle sizes were mixed in varying combinations. Three different compaction techniques (loose, tamped, vibration) were employed. The optimum packing density for both SSW and natural aggregates was achieved using the vibration compaction method. Since the combination of 50 % sand and 50 % SSW exhibited the best packing density for both materials, this bi-grade aggregate mixture was selected for the mix preparation. The mechanical tests (compressive strength, flexural strength) and durability assessment (bulk water sorptivity, rate of water absorption, chloride ion penetration) were performed to achieve the desired objectives. The specimens were exposed to two different curing regimes i.e., normal curing and heat curing at elevated temperature. A significant increase in compressive and flexural strength was observed with the increased content of SSW. A compressive strength as high as 140 MPa was obtained for the HPC mix containing SSW aggregates and steel fibers. The replacement ratio of SSW was optimized to achieve better strength and durability. Experimental results showed that heat curing was more effective than conventional curing methods in improving the performance of the concrete.