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Self-compacting concrete (SCC) has gained prominence in recent decades due to its inherent qualities, particularly its ability to compact autonomously. SCC proves invaluable in scenarios where traditional compaction is challenging due to placement conditions or the presence of close space reinforcement. This study focuses on evaluating the structural performance of lightweight self-compacting concrete (LWSCC) columns confined with glass fiber-reinforced polymer (GFRP) and steel tube (ST) subjected to cyclic loading. The LWSCC columns, denoted as LWSTC, are designed with inner steel tubes and outer GFRP tubes, imparting corrosion resistance and reduced weight alongside enhanced ductility. Through quasi-static loading, five fabricated LWSTC columns were subjected to assess their structural response under dynamic effects. The investigation delves into three key variables: axial load ratio, reinforcement ratio, and the replacement ratio of coarse lightweight expanded clay aggregate (LECA) in the fabricated LWSTC columns. A comprehensive analysis of various parameters, including skeleton curves, ductility, hysteretic cycles, damage modes, dissipation of energy capacity, stiffness behavior, strain spreading, and strength reduction, was conducted on the LWSTC columns. The findings reveal that the replacement of LECA with natural aggregates has an insignificant impact, whereas varying the axial load ratio significantly influences the structural behavior of LWSTC. Notably, LWSTC exhibits a remarkable 121% higher horizontal load capacity compared to counterparts using natural aggregate. Furthermore, LWSTC demonstrates superior axial strength and enhanced capability for energy dissipation.

Geopolymer, a novel binder material, possesses the potential to replace conventional cement completely. Recent studies have investigated the incorporation of various nanomaterials (NMs) into geopolymer concrete (GPC) to enhance its properties. Nanotechnology, an emerging field of study, has garnered significant attention in recent decades due to its groundbreaking research and practical applications. This comprehensive review aims to elucidate the effects of nanomaterial inclusion on the workability, strength, durability, and physical and microstructural characteristics of GPC. The properties have been meticulously examined, reviewed, and discussed. Over 190 research and review articles were reviewed, analyzed, and presented to develop a database containing critical properties of GPC modified with different doses and types of NMs. The influence of introducing diverse kinds and doses of NMs on GPC behavior was assessed. Historical trends, current tendencies, challenges, and the benefits and limitations of NM-modified GPC were explored. According to this review, incorporating NMs is promising for developing high-strength or high-performance GPC. It significantly improves mechanical, microstructural, and durability properties by providing additional calcium-silicate-hydrate, calcium-aluminate-silicate-hydrate gel, and nano-filling effects in the GPC matrix. This advancement will enable the construction industry to realize the potential of NM-enhanced GPC successfully. The present review demonstrated that the geopolymer concrete showed enhancements in engineering properties and effectiveness when modified with different types of nanomaterials and tested under different conditions. The current study also presented some challenges and research gaps that should be addressed in future research studies.

Waste tyre rubber has become an environmental and health concern that needs to be sustainably managed to avoid fire hazards and save natural resources. This research work aims to study the structural behavior of glass fiber reinforced polymer (glass-FRP) reinforced rubberized concrete (GRC) compressive elements under monotonic axial compression loads. Nine GRC circular compressive elements with different axial and crosswise reinforcement ratios were fabricated. All the elements were 300 mm in diameter and 1200 mm in height. A 3D nonlinear finite element equation (FEM) was suggested for the GRC compressive elements using a commercial package ABAQUS. A parametric study has been done to examine the effect of various parameters of GRC elements. The test outcomes revealed that the ductility of GRC elements ameliorated with the lessening in the spaces of glass-FRP ties. The addition of rubberized concrete improved the ductility of GRC elements. The damage to GRC elements occurred due to the vertical cracking along the height of the elements. The estimates of FEM were in close agreement with the test outcomes. The suggested empirical equation depending on the 600 test elements, which considered the lateral confinement effect of FRP ties, presented higher accuracy than previous equations.

This study investigates the potential of metakaolin as a mineral admixture to enhance the performance of concrete mixtures with varying proportions of recycled aggregates (RA). Sixteen distinct concrete combinations were formulated by substituting natural aggregates (NA) with RA at 0 %, 50 %, 75 %, and 100 % and incorporating metakaolin at 0 %, 5 %, 10 %, and 15 % as a replacement for cement. Experimental investigations were conducted to evaluate the effects of metakaolin (as a cement replacement) and RA (as a replacement for NA) on key concrete characteristics, including density, water absorption, compressive and tensile strength, and acid resistance. The results revealed that an increase in RA reduced mechanical properties, such as compressive strength, tensile strength, and dry density. Additionally, RA-based concrete mixtures exhibited higher water absorption and void volume than those with natural aggregates. However, including metakaolin in RA-based concrete significantly reduced the void volume and water absorption. The optimal proportion of metakaolin substitution was 15 %, resulting in the best overall performance for RA-based concrete mixtures. Notably, the highest compressive and splitting tensile strength (41.6 MPa and 4.3 MPa, respectively) were observed at 90 days in mixtures with 0 % RA and 15 % metakaolin. Similarly, the highest hardened density and lowest water absorption (2494.7 kg/m3 and 4.7 %, respectively) were recorded in samples with 0 % RA and 15 % metakaolin. Furthermore, concrete mixes containing 15 % metakaolin and 50 % RA demonstrated comparable qualities to conventional concrete, indicating that sustainable concrete can be produced by utilizing a significant quantity of waste concrete (15 % metakaolin and 50 % RA) without compromising strength criteria. This study sheds light on the potential of incorporating metakaolin and recycled aggregates as environmentally friendly alternatives in the construction industry, contributing to sustainable and eco-conscious practices.

Around the globe, natural reserves are depleting consistently. In this undeniable situation, it has become essential to find out substitute resources for the ingredients of cement concrete. To encounter this issue, the present study aims to utilize electronic waste (e-waste) as a substitute source of natural aggregates in the production of concrete. In this experimental-based investigation, shredded e-waste is utilized as a partial replacement of coarse aggregate (CA) in concrete with a constant volume replacement of 30% to study the mechanical, durability, and microstructural features. However, to cope with the poor mechanical efficiency, and brittleness of e-waste concrete, polypropylene fibers (PPF) were utilized in concrete. The testing results show that the mechanical efficiency of concrete was reduced by the replacement of natural CA with e-waste aggregate. Fibrous materials have a better impact on the mechanical efficiency of e-waste concrete. The incorporation of 0.5% dosage of PPF, as by volume fraction, in concrete, resulted in an increment in flexural strength and splitting tensile strength (STS) values of about 42% and 78%, respectively. However, the permeability-based durability parameters (sorptivity coefficient, chloride penetration, and porosity) are inversely influenced by an enhanced dosage of PPF. Scanning electron microscopy (SEM) showed that the incorporation of PPF resulted in improved microstructure while the incorporation of e-waste aggregates led to a weak internal matrix. The significance of this research work is the reduction of elevated consumption of natural resources in concrete production accompanied by the improvement in the efficiency of e-waste aggregate concrete by the incorporation of a suitable dosage of fiber reinforcement to make it more practical and sustainable.

Geopolymers (GOPL) can play a vital role in the sustainability of concrete construction. The addition of nanoparticles and micro-fibers to GOPL can improve the mechanical and microstructural performance by densifying the matrix and providing the bridging effect against the internal cracking mechanism. Therefore, an extensive investigation on the improvement of the various characteristics of the GOPL is required to make it feasible for practical applications. Moreover, the combined effect of nanoparticles and micro-fibers on various features of GOPL needs further insights. This study investigates the microstructural, mechanical, fracture, and toughness performance of micro-basalt fiber (MBF)-reinforced coal ash-made GOPL using different proportions of nano-sodium oxide at ambient curing conditions. The percentage of nano-sodium oxide examined in the present study varied from 0% to 4% by weight. The MBF amount is kept the same for all fabricated samples at 0.5% by weight. Scanning electron microscopy is used for assessing the microstructural cracking and failure behavior of GOPL pastes. The findings of the present study divulged that the usage of 3% nano-sodium oxide in MBF-reinforced GOPL mix presented the highest increase of 29%, 55%, 24%, and 60% for the compression strength, flexure strength, fracture toughness, and impact strength, respectively. Further increase in the content of nano-sodium oxide prompted the agglomeration of nanoparticles leading to a reduction in the performance of the GOPL. The outcomes of scanned electron microscopy delineated that the addition of nano-sodium oxide refined the interfacial regions and promoted the polymerization process of the GOPL which enriched the microstructure and fabricated a highly densified GOPL paste.

This study has endeavored to produce eco-friendly coal ash-incorporated recycled aggregate concrete (FRAC) by utilizing wastewater effluents for environmental sustainability. The mechanical and durability efficiency of the FRAC manufactured were explored using different kinds of effluent by performing a series of tests at various ages. The considered kinds of effluent for the mixing of FRAC were collected from a service station, as well as fertilizer, textile, leather, and sugar factories. Scanning electron microscopy (SEM) was utilized to judge the microstructural behavior of the constructed concrete compositions. The outcomes revealed that using textile factory effluent in the manufacturing of FRAC depicted peak compressive and split tensile strength improvements of 24% and 16% compared to that of the FRAC manufactured using potable water. The application of leather factory effluent for the manufacturing of FRAC portrayed the highest water absorption (13% better than the control mix). The application of fertilizer effluent in the manufacture of FRAC presented the greatest mass loss (19% enhanced than the control mix) due to H2SO4 solution intrusion and the ultimate chloride ion migration (16 mm at twenty-eight days of testing). The summation of coal ash improved the mechanical behavior of the concrete and also caused a reduction in its durability loss of. The SEM analysis depicted that the textile factory effluent presented the most densified microstructure with the development of ettringite needles and CSH gel having refined the ITZ.