The exponential growth in industrialization, urbanization, and population has subsequently increased the accumulation of different wastes to hazardous levels. Among these, electronic waste (E-waste) poses a serious threat to the environment with its production rising due to technological advancements worldwide. Therefore, recycling E-waste as an alternate aggregate replacement material in the construction industry can be advantageous in managing this waste stream. This study aims to present a comprehensive insight into the integrated applications of E-waste concrete composite materials in the construction industry including applications to increase the environmental sustainability of concrete structures. This review starts with an illustration of the environmental issues caused by E-waste, elucidates its sources and prevailing recycling practices, and investigates its utility as supplementary cementitious materials. This discussion is further followed by an analysis on recycled E-waste plastic aggregate concrete (RPAC) composites, covering their fresh properties, mechanical properties, thermal properties, durability, and serviceability performance. Besides, this paper also explores the evaluation of the utilization of E-waste fibers (E-fiber) as well as the application of E-waste glass (E-glass) from cathode ray tubes (CRT) in concrete. Based on the detailed review, the positive aspects and the restrictions associated with utilizing E-waste in construction have been highlighted.

This paper presents a new energy dissipation system composed of multistable cosine-curved domes (CCD) connected in series. The system exhibits multiple consecutive snap-through and snap-back buckling behavior with a hysteretic response. The response of the CCDs is within the elastic regime and hence the system's original configuration is fully recoverable. Numerical studies and experimental tests were conducted on the geometric properties of the individual CCD units and their number in the system to examine the force–displacement and energy dissipation characteristics. Finite element analysis (FEA) was performed to simulate the response of the system to develop a multilinear analytical model for the hysteretic response that considers the nonlinear behavior of the system. The model was used to study the energy dissipation characteristics of the system. Experimental tests on 3D printed specimens were conducted to analyze the system and validate numerical results. Results show that the energy dissipation mainly depends on the number and the apex height-to-thickness ratio of the CCD units. The developed multilinear analytical model yields conservative yet accurate values for the dissipated energy of the system. The proposed system offered reliable high energy dissipation with a maximum loss factor value of 0.14 for a monostable (self-recoverable) system and higher for a bistable system.

This study evaluated the impact of nano silica (NS) and nano metakaolin (NMK) on high-strength concrete (HSC). Portland cement was partially replaced with varying amounts of NS and NMK, both individually and in combination. Portland cement was partially replaced with varying percentages (1, 2, 3, and 4 wt%) of NS and (2, 4 and 6 wt%) of NMK in individual mixes. Four concrete mixtures were formulated using a combination of NS and NMK. The physical properties (slump, consistency, and setting times), mechanical properties (compressive and tensile strengths at 28 days), and microstructural analysis (X-ray diffraction (XRD) and energy-dispersive X-ray (EDX)) were conducted on both the individual and combined mixtures, along with the control mix. Radiation shielding properties of the concrete were conducted. The Monte Carlo simulation code and the Phy-X program were used to examine the efficacy of these combinations in shielding against ionizing radiation, e.g., gamma rays and fast neutrons. The results showed NS and NMK reduced slump in HSC, primarily due to increased water demand and a denser structure. Combined use led to a more significant reduction than individual. Increased NS and NMK content led to higher water demand but shorter setting times. NS improved compressive and tensile strengths, reaching a maximum of 10.5% and 5.6%, respectively, at replacement 3% NS. NMK increased compressive and tensile strengths of 11.7% and 6.3%, respectively at replacement 4% NMK. The combined mixture 1% NS + 4% NMK mixture, demonstrated enhancement in compressive and tensile strengths by 14.2% and 7.7%, respectively, compared to the control mix. XRD and EDX analyses confirmed that NS and NMK enhanced the formation of calcium silicate hydrate and calcium aluminate hydrate through pozzolanic reactions. The linear attenuation of the concrete samples was NMK4 < CM2 < NS3 < C0. The sample containing NMK demonstrated the best value for the linear attenuation coefficient of gamma rays and a rise in FCS, indicating that it is an excellent barrier against both gamma rays and neutrons. These findings demonstrate that NS and NMK significantly enhance HSC strength and radiation shielding, offering safer and more durable concrete for nuclear and medical facilities.

This study investigated the viability of rice husk-derived biochar (RHB) as a partial substitute for cement in concrete. The used RHB, characterized by a novel chemical composition abundant in silicon and aluminum oxides, was incorporated into ordinary concrete at increasing substitution ratios up to 25% by cement weight. A comprehensive evaluation was conducted to assess the influence of RHB on various properties of concrete, including physical (setting time, standard consistency, workability), mechanical (compressive and tensile strength), microstructural (XRD, and EDX), and radiation shielding characteristics. The results indicated that RHB marginally increased cement setting time, with a maximum 7.14% increase observed at a 25% replacement level. However, it significantly increased water demand for standard consistency, reaching 35.7% at 25% replacement. The increased water demand correlated with a reduction in workability, with a maximum slump reduction rate of 57.3% at a 25% replacement level. The optimal replacement levels for mechanical strength enhancement were at 10% for compressive strength and 15% for tensile strength, achieving improvements of 13.74% and 9.48%, respectively. Additionally, Monte Carlo simulation code and PhyX software were employed for assessing gamma and fast neutron radiation attenuation characteristics of concrete. Gamma-ray attenuation tests revealed moderate improvements in the concrete’s gamma-ray shielding capacity. Interestingly, the 15% RHB sample demonstrated a higher linear attenuation compared to the other samples, a result of its increased density. On the contrary, the 25RHB sample is less valuable. The 15RHB sample had the highest value for FCS (0.090 cm⁻¹) indicating its efficacy as a neutron shield.