A review of cementitious alternatives within the development of environmental sustainability associated with cement replacement.

The environmental conditions of sustainable improvement in manufacturing consist of the application of secondary raw materials in the design and structure of new structures. Presently, the demand to construct new structures is growing rapidly, especially in the developed world. All of the construction and demolition (C&D) waste is deposited in open landfills in easily reachable spaces, which leads to numerous environmental problems. The utilization of this waste in concrete will help in sustainable and greener development. The main goals of using waste, by-products, and recycled materials to develop sustainable concrete are to reduce carbon dioxide emissions, which are a cause of environmental pollution and climate change, and to enhance exploitation of waste, which creates problems of disposal that can be solved by completely or partially replacing concrete components. This paper aims to provide a comprehensive overview of the published literature on the replacement of cement in concrete such as rice husk ash (RHA), olive stone biomass ash (OBA), recycled coal bottom ash (CBA), and recycled palm oil fuel ash (POFA), and its effects on the characteristics of concrete like workability, density, compressive strength, splitting tensile strength, flexural strength, shrinkage, and durability. Also, this paper aims to review the impact of the replacement of cement on sustainability. The author has also included recommendations for future research.