Geopolymer cement based on alkali activated slag

Abstract

The aim of this investigation is to prepare geopolymer cement by mixing various amounts of granulated blast furnace slag (GBFS) with Fly ash (FA) and cement kiln dust (CKD). Seven blends are prepared using 100 % slag , 95% slag+5% CKD or fly ash , 90% slag + 10% CKD or Fly ash and 85% slag + 15% CKD or Fly ash . The dry mixes with the different mixing ratios are activated by the alkaline activator (AA) 6% sodium hydroxide solution and 10% by volume liquid sodium silicate, the w/s ratio used is 0.24. The pastes are moulded into 1 inch cubic moulds and left within the moulds at 100% relative humidity for 24 hrs, then demoulded and cured under tap water for 1,3,7,28,90 and 180 days. At each hydration time, compressive strength, combined water , bulk density , total porosity are determined . X-ray diffraction measurements showed CSH as the main hydration constituent of the geopolymer structure being amorphous and glass-like. The results indicate that the mix containing 85% slag + 15% fly ash give the best physico chemical and mechanical properties of geopolymer cement .