Preparation of geopolymer insulating bricks from waste raw materials

Insulating geopolymer samples were prepared from cheap sources, namely, the powder residue from the production of clay bricks (clay bricks waste), slaked lime waste from acetylene production and waste aluminum trimmings from workshops. 0.5% caustic soda was used, together with slaked lime as alkaline activator. De-aluminated kaolin, a waste from the alum industry, was also added as binding agent to substitute part of the clay bricks waste. Hydrogen produced from reaction between aluminum and alkalis induced the formation of pores inside the geopolymer matrix. It was found that using 5% (by weight) aluminum trimmings and substituting 15% of clay bricks waste by de-aluminated kaolin was enough to raise the porosity above 50%, thus producing light bricks of densities in the 1000 kg.m(-3) range. The compressive strength of these bricks was about 1.4 MPa and their thermal conductivity as low as 0.26 W.m(-1).K-1. (C) 2019 Elsevier Ltd. All rights reserved.