Replacing river sand in concrete: a review of emerging sustainable fine aggregate materials

In recent times, sourcing alternatives to river sand (RS) as a fine aggregate (FA) has been on the rise for sustainable construction, due to an increase in construction activity that has led to the depletion and scarcity of RS. This review synthesizes the characteristics and performance of various sources of FA, such as rock-, agro waste-, and waste polymer-based for construction applications, focusing on formation, physical and chemical characterization, and their influence on concrete (workability and mechanical behaviours). The review revealed that not more than 35% rock-based FA is suitable for RS replacement as FA in concrete. Moreover, the replacement of RS with waste polymer-based materials, such as polyethene terephthalate Polypropylene expanded polystyrene and melted plastic crushed fine aggregate should not exceed 5, 10, 10, and 6%, respectively, to produce lightweight concrete for environmental sustainability. In addition, the replacement of RS with agro-waste, such as rice husk, in concrete indicated that not more than 30% should be used, respectively, to enhance concrete strength and durability. Therefore, this review suggests that sourcing river sand (RS) alternatives to address environmental problems emanating from waste that threatens the ecosystem becomes necessary to reduce pressure on the use of RS for sustainable construction. However, the use of multiple RS alternatives should be considered in future studies, while academic, industry, and government collaboration is crucial for the establishment of policies and frameworks to promote the adoption of RS alternatives for environmental sustainability.