Increasing the reaction kinetics of alkali-activated fly ash binders for stabilisation of a silty sand pavement sub-base

The paper addresses several options to improve the reaction kinetics of alkali-activated low-calcium fly ash binders for soil stabilisation in road platforms. For that purpose, an experimental programme was established to assess the strength evolution, with time, of different binders, based on ash, lime, sodium chloride and alkali solutions, applied in the stabilisation of a silty sand. The tests included unconfined compression strength tests, triaxial tests and seismic wave measurements performed at different curing periods. The results were compared with a binder made of Portland cement and a commercial additive specifically designed for soil stabilisation in road applications. The activated ash mixtures with lime were the most performing producing a significant increase in the reactions development and, consequently, in the strength gain rate. The sodium chloride significantly improved the lime and lime-ash mixtures, but provided only a slight improvement in the activated ash mixtures.