Mechanical and durability characteristics of flyash-based soil-geopolymer mixtures for pavement base and subbase layers

ABSTRACT

In this research study, medium and high plastic soils were utilised in evaluating the physical, microstructural, mechanical and durability characteristics of fly ash-based soil-geopolymer mixtures. Class F fly ash was used with a mixture of sodium silicate and sodium hydroxide to prepare fly ash-based soil-geopolymer mixtures. An experimental design was developed incorporating various combinations of fly ash content, sodium silicate to sodium hydroxide ratio, and sodium hydroxide concentration. Several mixtures were cured at different conditions, and tested for unconfined compressive strength. Based on developed regression model and sensitivity analysis various mixtures from each soil type were selected for further evaluation. The resilient modulus, dynamic modulus, durability, FTIR, XRD, and scanning electron microscopy (SEM) tests were also conducted for the selected mixtures. The results indicated that soil-geopolymer demonstrated satisfactory performance under static and dynamic loadings, and passed the wet and dry durability test criteria. SEM analysis revealed that microstructure and morphology of the mixtures displayed formation and stable growth of geopolymerisation during the progression of curing period. XRD and FTIR results also indicated the formation of geopolymer products in soil-geopolymer mixtures. The mechanical, durability, and microstructural characteristics revealed that the soil-geopolymer mixtures have an immense potential to be used as pavement subbase and base layers.

KEYWORDS:

• Geopolymer
• fly ash
• soil-geopolymer
• unconfined compressive strength
• resilient modulus
• dynamic modulus
• durability
• soil-cement
• road base and subbase

Acknowledgements

Authors would like to thank the University of Louisiana at Lafayette, USA for the financial support. Special thanks are also extended to Syfur Rahman and Mr Mark LeBlanc for their unconditional support, in assisting in experimentation and equipment use.

Disclosure statement

No potential conflict of interest was reported by the authors.