Geosynthesis of building and construction materials through alkaline activation of granulated blast furnace slag

This article investigated the feasibility to synthesise geopolymer bricks from Granulated Blast Furnace Slag (GBFS) using alkaline activators without addition of sodium silicate or silica reactive source. Sodium hydroxide (NaOH) is a typical alkaline solution used in geopolymerisation compared to KOH with addition of silicate solution used as a catalyst to enhance the dissolution process. However, a comparative study between the two alkaline activators in the absence of silica solution are very scarce and limited. For this purpose, this article investigated the effect of type of alkali (NaOH and KOH) on unconfined compressive strength (UCS) with the aim to establish the best alkali activator that possess high activation potential and favours GBFS geopolymerisation. In addition, the effect of alkali concentration, liquid-solid ratio, curing temperature and time on the physical and mechanical properties of geopolymer bricks were investigated using UCS, SEM micrographs, XRD analysis, water absorption, and bulk density. Metal leachability and durability of the synthesised geopolymer brick was also investigated. The results show that geopolymer brick prepared with NaOH favours GBFS geopolymerisation. The optimum curing conditions that yielded the highest UCS of 72 MPa were 15 M NaOH, liquid to Solid ratio of 0,15, curing temperature and time of 80 degrees C and 5 days. The highest UCS was due to formation of a dense, less porous and more amorphous microstructure. The synthesised geopolymer brick met the minimum required UCS and the water absorption % to be used as facing and solid mansory brick in accordance with ASTM C126-99 and ASTM C216-07a respectively. (C) 2020 The Author(s). Published by Elsevier Ltd.