Estimating the compressive strength of geopolymer recycled concrete

Research has shown that different types of waste from industrial and agricultural activities can be used as a partial or complete substitute for traditional concrete materials to save costs and conserve natural resources. This study, therefore, explores the use of geopolymer binders (coal fly ash (CFA) and rice husk ash (RHA)) as a partial substitute for cement (0%, 5%, 5%, and 15% for CFA; and 0%, 5%, 10%, and 20% for RHA, by wt of cement) and cupola furnace slag (CFS) as a coarse aggregate (0%, 5%, 10%, and 30%) of prod. A mixture of 8 M sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) as alkaline activators was used to synthesize geopolymers. Tests such as workability and compressive strength were performed on both fresh and hardened GPRC. The results showed that incorporating 15%CFA, 20%RHA, and 30%CFS increases the workability by 68.57%, but the compressive strength is slightly reduced. It can be concluded that the addition of 5% CFA, 10% RHA, and 10% CFS (i.e., GPRC2) gives an optimum compressive strength of 21.60 N/mm(2) and 23.55 N/mm(2), respectively, at 28-d and 56-d, compared to a minimum strength requirement of 20 N/mm(2). (C) 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Confer-ence on Advanced Materials Behavior and Characterization.