Mechanical and durability properties of a soil stabilised with an alkali-activated cement

Abstract

Alkali-activated cements (AAC) have been extensively studied for different applications as an alternative to Portland cement (which has a high carbon footprint) and due to the possibility of including waste materials such fly ash or slags. However, few works have addressed the topic of stabilised soils with AAC for unpaved roads, with curing at ambient temperature, where the resistance to wetting and drying (WD) as well as the mechanical properties evolution over time is particularly relevant. In this paper, silty sand was stabilised with an AAC synthesised from low calcium fly ash and an alkaline solution made from sodium silicate and sodium hydroxide. The evolution of stiffness and strength up to 360 days, the tensile strength, and the performance during WD cycles were some of the characteristics analysed. Strength and stiffness results show a significant evolution far beyond the 28th curing day, but still with a reasonable short-term strength. Strength parameters deduced from triaxial tests were found to be very high with stress–strain behaviour typical of cemented soils. Durability properties related to resistance to immersion and WD cycles were found to comply with existing specifications for soil–cement, giving validity for its use as soil–cement replacement.

Keywords:

• fly ash
• alkali-activated cement
• soil improvement
• resistance to immersion
• curing time

Acknowledgements

The authors would also like to acknowledge the Chemical Engineering Department of University of Porto, namely Professors Fernão Magalhães and Adélio Mendes, for the use of the Particle Size Analyser; the company Pegop – Energia Eléctrica SA which runs the thermoelectric power plant of Pego, for the supply of fly ash.

Disclosure statement

No potential conflict of interest was reported by the authors.