Fly Ash Based Geopolymer Bricks: A Sustainable Construction Material

Abstract

Considering the increasing demand for sustainable and environment friendly construction materials, the feasibility of fly ash based alkali activated geopolymer bricks, has been aimed in this project as an alternative to ordinary bricks. Geopolymers are amorphous to semi crystalline alumina silicate polymer originated by inorganic polycondensation reaction of solid alumina silicate with highly concentrated alkali hydroxide or silicate solution. Production of building materials, particularly bricks using fly ash is considered to be one of the solutions to the ever increasing fly ash disposal problems in the country. Fly ash based geopolymer with alkali liquid to binder ratio as 0.4 and sodium silicate to sodium hydroxide ratio as 2.5 was studied in this project. Geopolymer bricks of size 230 mm × 110 mm × 70 mm were optimized by varying the molarity of NaOH, percentage of extra water added, curing conditions. The compressive strengths, water absorption and durability of optimized fly ash based geopolymer bricks were compared with cement bricks and country burnt bricks. Considering the economical aspect, the mix proportions were changed with fly ash to fine aggregate ratio as 1:6 and molarity of NaOH as 5M. Fine aggregate as river sand, M sand and quarry dust were also studied to find the most affordable brick.