The mining sector generates a considerable amount of waste stone and tailings, which constitute a substantial hazard to the ecology. The most prevalent method of disposing of these industrial wastes is by dumping, which adds to soil deterioration and water contamination and also takes up valuable land. Fortunately, it can be recycled in a variety of ways, including the promising geopolymerisation technique, which converts waste into value. This article discusses recent advances in the production of mine tailings-based geopolymers composites (MT-GPC) from waste and industrial by-products as a potentially sustainable construction material. Besides, focusing on the following aspects: economic and production perspective; environmental consequences and waste disposal; physical and chemical properties; mechanical properties; durability properties; microstructure properties; thermal properties; and potential applications of MT-GPC.
The production of cement results in the emission of much carbon dioxide, which contributes to undesirable environmental impacts such as climate change and global warming. These phenomena have rekindled interest in utilizing a variety of industrial waste products to produce geopolymer (GP) composites and alkali-activated (AA) binders in order to reduce the usage of ordinary Portland cement in building construction. Waste red mud (RM), also known as bauxite residue, is one of these hazardous radioactive waste materials that is formed as a by-product of Bayer's aluminum manufacturing process. This paper conducts a systematic review of the literature on the use of RM and slag in the production of red mud-slag geopolymer (RM-SGP). An overview of the economic and environmental impacts, physical and chemical properties, production, distribution, classification, and potential applications of RM are presented. Besides, recent advancements in the usage of RM and slag for geopolymer production are described in terms of physical, mechanical, durability, and microstructure properties. Moreover, this study attempts to chart a route toward a realistic valorization that reflects both real and perceived concerns, such as radioactivity, leaching, and the life cycle assessment of red mud geopolymer (RM-GP). The potential use of RM-SGP production indicates the need for further studies into the mixture proportion and combination of these two raw ingredients with other cementitious materials leading to new energy-saving and affordable building products and processes. Also, it is recommended that research efforts be directed toward economic, life cycle, and environmental assessments.
In recent decades, several studies have considered the use of plastic waste as a partial substitute for aggregate in green concrete. Such concrete has been limited to non-structural applications due to its low strength. This raises whether such concrete can be enhanced for use in some structural applications. This paper reports an attempt to develop a structural-grade concrete containing plastic waste aggregate with high proportions of substitution and confined with carbon fiber reinforced polymer (CFRP) fabrics. Experimental research was conducted involving the casting and testing 54 plain and confined concrete cylinders. A concrete mixture was designed in which the fine aggregate was partially replaced by polyethylene terephthalate (PET) waste plastic at ratios of 0%, 25%, and 50%, and with different w/c ratios of 0.40, 0.45, and 0.55. The results show that confinement has a substantial positive effect on the compressive behavior of PET concrete. The enhancement efficiency increases by 8-190%, with higher enhancement levels for higher substitution ratios. Adding one layer of CFRP fabric raises the ultimate strength of samples that have lost compressive strength to a level close to that of unconfined samples not containing PET. This confinement is accompanied by an increase in the slope of the stress-strain curve and greater axial and lateral strain values at failure. For the specimens confined by CFRP fabric, PET aggregate can be used as a partial substitute for sand at a replacement ratio of up to 50% by volume for structural applications. This paper also considers the ability of existing models to predict the strength of confined-PET concrete circular cross-sections by comparing model predictions with experimental results. The strength of confined PET concrete elements can't be accurately predicted by any of the models that are already out there. It's important to come up with a new model for these elements.
Ultra-high-performance concrete (UHPC) is a type of cement-based composite for new construction and/or restoration of existing structures to increase service life. It is an innovative composite material that can be a suitable alternative to concrete structures exposed to aggressive conditions. After decades of research and development, a wide range of commercial UHPC compositions have been produced worldwide to cover a growing number of applications and a growing demand for high-quality construction materials. UHPC has significant advantages over regular concrete, but its use is limited due to limited design codes and prohibitive cost. Therefore, a comprehensive investigation of the durability characteristics of UHPC is essential to provide fundamental information for material testing requirements and procedures and expand its practical applications. Part I reviewed the developments, principles, and raw materials of the UHPFRC. Part II reviewed the hydration and microstructure of the UHPFRC. Part III reviewed the fresh and hardened properties of the UHPFRC. This Part IV covers the durability properties, cost assessment, applications, and challenges of the UHPFRC. Part V covers the mixture design, preparation, mixing, casting, and curing of the UHPFRC. This review is expected to advance the fundamental knowledge of UHPC and promote further research and applications of UHPC.
