Meeting the requirements of the construction market and addressing the scarcity of virgin materials pose significant challenges in increasing the required concrete amounts for construction projects. This study explores the workability, density, and strength properties of sustainable concrete containing partial replacement of natural sand with iron ore waste (IOW) as a fine aggregate. In the first group, four concrete mixtures were prepared using different percentages of IOW (0 %, 15 %, 30 %, and 60 %) to replace natural sand. Basalt fiber was added into the second group of four concrete mixtures to enhance fiber-reinforced concrete (FRC) in the volume of 2 % of the cement weight. High volume of supplementary cementitious materials (SCMs) including fly ash (FA) and silica fume (SF) were used to replace cement in proportions of 35 % and 15 %, respectively to achieve sustainable concrete with low cement content. The results obtained show that an increase in replacement levels of IOW led to a decrease in the slump value of the concretes, from 120 mm to 80 mm, with a reduction rate of 33 %. The addition of 30 % IOW as fine aggregate led to an increase in the compressive strength of concretes by 47.34 %. Scanning electron microscopy (SEM) images revealed that the high porosity of IOW contributed to these changes in concrete properties. It is recommended to optimize concrete mixes based on the specific needs of civil engineering applications. This includes selecting different mix designs tailored for the desired structural performance, durability, and environmental conditions. Using IOW as fine aggregate in the concrete mix will help conserve resources for the next generations and enhance waste management, leading to greater sustainability in the construction industry.

Dynamic strain aging (DSA) is a sudden increase in the strength of a material under certain combinations of temperatures and strain rates. Despite the phenomenon being reported in several other studies, the literature still lacks a specific constitutive model that can physically interpret its effect. Therefore, this work proposes a modification based on physical parameters to the Voyiadjis and Abed (VA) model to account for the effect of DSA in C45 steel. The resulting modified model is then coupled with an energy-based damage model to further capture the effect of material softening. Previously, in VA model, it was assumed that the total activation energy for overcoming the obstacles without external work remains the same which works well in the absence of DSA. However, during DSA, the mobile dislocations are pinned by the diffusing solute atoms. This results in an increase in the total activation free energy needed by the dislocations to overcome the obstacle. Thus, an increase in strength is observed. It is shown in the current work that utilizing the concept of increased solute concentrations at local obstacles, in conjunction with the physical description that the VA model is based upon, successfully captures the phenomenon of DSA in C45 steel. In addition, the metal experiencing softening after reaching its ultimate strength is due to the significant growth of voids and cracks within the microstructure. To capture this behavior, an energy-based damage parameter is incorporated into the proposed model. The coupled plasticity-damage model shows a good comparison with the experimental results.

This paper explores the challenge of accurately modeling Dynamic Strain Aging (DSA) in metals using numerical models. The proposed modification to the Voyiadjis-Abed (VA) model addresses the limitations of current models by introducing an additional microstructures-based parameter to capture the effect of DSA. The modified VA model considers the impurity-dislocation interactions based on the concentration and diffusion kinetics of impurity atoms. Results show successful DSA capture in commercially pure Niobium and Vanadium using physical and microstructural parameters. This study provides a promising approach for accurately modeling DSA activation in bcc metals, enabling future research.

Dynamic Strain Aging (DSA) is the irregular increase in metal strength that results from the diffusion of impurity atoms and their interactions with dislocations during plastic deformation at specific strain rates and temperatures. Commercially Pure Titanium (CP–Ti) has been reported to exhibit DSA over a broad range of temperature and strain rates during plastic deformation owing to the impurity atoms diffusion. The current work focuses on the modification of the physical-based Voyiadjis Abed (VA) model by introducing an additional term, based on the concentration and diffusion kinetics of different impurities, to capture DSA in CP-Ti. The analysis of diffusion parameters indicates that the hydrogen impurity diffuse into the dislocation core and interact with the mobile dislocations, thus defining the temperature range for the activation of DSA at low and high strain rates. The results show that the modified VA model could capture DSA in CP-Ti over a wide range of strain rates and temperatures when the recommended novel modification based on physical and microstructural parameters was introduced.

Desertification stands as a major global issue, while the scarcity of renewable energy sources continues to be a growing concern. To address these challenges, the use of desert sand as a fine aggregate in sustainable concrete has been explored. Desert sand offers numerous advantages such as environmental protection, cost savings, and energy efficiency. This paper examines the impact of treated desert sand on the mechanical and microstructural properties of sustainable concrete. The results of this study reveal that the highest compressive strength was achieved with a 50% replacement level of treated desert sand. The concrete mixture with 50% desert sand achieved the highest 28-day compressive strength at 61.06 MPa. Conversely, the lowest 28-day compressive strength of 41.73 MPa was observed in the concrete mix containing 100% treated desert sand while the control mix with 0% treated desert sand attained a 28-day compressive strength of 48.7 MPa. As the proportion of treated desert sand increased, the workability of concrete decreased. The slump value, which was initially 130 mm for the control mix, dropped to 80 mm in the concrete mix composed of 100% treated desert sand. However, the flexural and tensile strengths tended to decrease as the amount of desert sand increased, particularly beyond a 25% replacement level. The addition of desert sand improves compactness and reduces pores in the samples, as observed through Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy Analysis (EDS) analysis. The results suggest that desert sand can be effectively treated using different treatment methods and used as a fine aggregate in various applications within the construction industry. This research sheds light on the potential of desert sand in sustainable concrete production, contributing to environmental preservation and resource conservation efforts.