Mechanical and durability assessment of phosphogypsum- bauxite residue - fly ash-based alkali-activated concrete

Abstract

Phosphogypsum (PG), bauxite residue (BR), and fly ash (FA) are all by-products of different industries. This study presents the development of alkali-activated concrete (AAC) using industrial by-products like PG, BR, and FA. Therefore, the prime aim of this study is to analyze the mechanical and durability properties of the developed AAC. It is noteworthy to mention that the PG is replaced with FA at 10%, 20%, 30%, and 40% for a constant BR ratio. Subsequently, the results reveal that the optimum mix composition of the AAC is 20% BR, 20% FA and 60% PG (P6), resulting in a maximum compressive strength of 54.74 MPa. Additionally, water absorption, sorptivity tests, and the rapid chloride penetration test (RCPT) have been performed to assess the durability of the AAC, and P6 has exhibited the best resistance to the environment. Moreover, scanning electron microscope (SEM) and X-ray diffraction (XRD) test have been carried out to study the micro-characterization of the AAC. The fundamental parameters of the AAC are calcium alumino silicates hydrate gel (C-A-S-H) gel and sodium alumino silicates hydrate gel (N-A-S-H) gel, which play a crucial role in the development of the strength and durability of the AAC. Further, the leaching characteristics of the AAC show that all heavy metals are well solidified during the gel formation. Synergistically developed AAC can be used in construction applications such as foundations, pavements, and building materials as a substation of conventional cement concrete.