Valorization of waste as raw material in geopolymers synthesis for applications in civil construction

Abstract

Cement is widely used in civil construction. However, the increasing production of this material brings significant environmental impacts, such as high energy consumption and, most notably, elevated CO₂ emissions. In recent years, research has been conducted to find more eco-efficient materials, and one of the promising alternatives to replacing cement is the use of geopolymers. These materials are aluminosilicates activated by alkaline solutions, which can exhibit suitable mechanical properties and durability for application in civil construction. In the synthesis of geopolymers, by-products and industrial/agricultural waste rich in aluminosilicates can be used as raw materials. In this context, the main objective of this study was to identify the types of waste used as precursors in the synthesis of geopolymers applicable to civil construction. For this purpose, a systematic literature review was conducted, in which the following information was gathered: the waste's origin activity (industrial, urban, and agricultural), chemical composition, and granulometry. The main synthesis factors (types of activators, NaOH solution concentration, Na₂SiO₃/NaOH ratio, curing type, synthesis method) and their influences on the mechanical properties, microstructure, and durability of geopolymers made from residual materials were also discussed.