LAUSR

Abstract Sulphate-induced heaving in soils is a common problem caused mostly by the use of calcium-based binders in the stabilisation of sulphate-bearing soils. Sulphate-induced heaving is attributed to precipitation and growth of ettringite minerals in a high alkaline environment. A sustainable means of reducing sulphate-induced heaving by the addition of an additive called “RoadCem” (RC) to soils stabilised by calcium-based cementitious products has not been studied. RoadCem (RC) is an additive that is manufactured based on nanotechnology and comprises synthetic zeolite, alkaline metals and some complex activators as some of its constituents. This research is therefore concerned with the performance of a sulphate-bearing soil stabilised by partially substituting cement (CEM I) with ground granulated blast furnace slag (GGBS) and incorporation of marginal quantities of RC. Laboratory studies including oedometer free swelling testing, unconfined compressive tests and microstructural analyses of the phases of hydration in the stabilised soils were carried out. Results indicated a reduction in heave by about 67% when 1% of RC was included in the cementitious mix with 50% of the CEM I replaced by a combination of GGBS and RC. The use of RC in the stabilised soil was even more promising than that in which only GGBS was utilised to replace half of the CEM I proportion in the stabilised soil with the result indicating almost a 30% difference in heave reduction. Results also indicated an increase in the unsoaked strength of stabilised soil with RC inclusion compared to the stabilised mix without RC. Scanning electron micrograph studies revealed almost a complete elimination of heave-causing ettringite minerals under a 28-day hydration phase of the stabilised soil when using RC.