Using alkali-activated binders to improve uae dune sand

Abstract

Soil improvement is a technique that improves the soil engineering properties. Several chemical and mechanical techniques have been developed over the last decades to alter or improve poor soil conditions. Many of these chemical techniques use either cement or lime. These traditional techniques have proven efficiency and durability over many years of use despite environmental concerns. Alkali-activated binders (AABs) have shown potential for low energy, low cost and high strength alternative to these traditional cementitious materials. A preliminary study was conducted on the feasibility of using alkali activated mixture of fly ash and Groundgranulated blast-furnace slag (GGBFS) to stabilize local dune-sands. Several micro-and macro-characterization techniques are used to examine the suitability of these binders to improve these local soils. Two different precursors are employed as activators in this investigation namely sodium silicate solution (Na2SiO3) and sodium hydroxide (NaOH). The factors studied for the geopolymerization process were Na2SiO3/NaOH ratio, total ratio of activator solids by sand weight, and finally ratio of fly ash to GGBFS. The tested specimens were cured temperature of 45 degree Celsius for 24 hours to replicate UAE environmental condition. A maximum strength of 3.68 MPa was attained after 14 days of curing for mixture with a ratio of Na2SiO3/NaOH equal to 1 and 40%:60% of fly ash to GGBFS. The total binder to soil ratio for this mixture was 15% by weight.