Lightweight geopolymer fly ash sand: an alternative to fine aggregate for concrete production

The current study is aimed to evaluate and critically analyze the properties of Light Weight Geopolymer Fly Ash Sand (LWGFAS). LWGFAS has been prepared by geopolymerisation of the fly ash. Liquid solution of 4M NaOH, and Na2SiO3/NaOH=2 was used as an activator and post set heat treatment of 1 hour at 100 oC was applied for preparation of LWGFAS. The LWGFAS sample was analyzed for different physical and chemical parameters along with studies on mineralogy and alkali silica reactivity. The molar concentration of activator solution and duration of post set heat treatment plays vital role on the physical and mechanical properties (particularly specific gravity, bulk density and water absorption) of the Geopolymer fly ash sand. The specific gravity and water absorption of LWGFAS were 1.57 and 17.85% respectively. Experimental concrete mixes made with LWGFAS as a replacement of natural sand were evaluated for compressive strength and different durability properties of concrete. The study indicates that LWGFAS can be suitable for a wide range of applications in making concrete ranging from light weight in nature to normal weight concrete based on the physical and chemical characteristics of Geopolymer Fly Ash Sand.