Fly ash-based geopolymer as A4 type soil stabiliser

Abstract

The goal of this paper is the use of a fly ash with high unburned carbon which generally has lower demand in the market because, according to ASTM C618, it cannot be used in Portland cement concrete. Alkali-activated cements (AACs) based on this industrial by-product were prepared using granulated blast furnace slag (GBFS) and lime (L) as calcium sources. The AACs were used for A-4 type soil improvement. The unconfined compressive strength, flexure strength, and durability (volume change and mass loss) of the soil treated were evaluated. The results showed that under soaked conditions the compressive strength increased up to 119.4% at 7 days of curing and 78.6% at 28 days of curing. Additionally, the mass loss percentage after twelve (12) wetting and drying cycles was less than that allowed by Colombian specifications for stabilized soil. This demonstrated that it is possible to use this type of fly ash as an environmentally sustainable alternative to replace Portland cement as soil stabilizer in applications for road construction. The proposed solutions are thus considered competitive with current chemical stabilization techniques. However, further studies on the long-term performance of AACs stabilized soils, and the cost of applying AACs in soil stabilization are worth being conducted.