Effect of Alkali-Activated Fly Ash on Shrinkage Characteristics of Expansive Soil

Expansive soils are known as problematic due to their significant volume change during seasonal moisture fluctuation. The present study reports the suitability of alkali-activated fly ash as an alternate binder, to conventional stabilizers like cement, used to mitigate the volumetric shrinkage of expansive soil. Alkali-activated fly ash is an alternative binder in which liquid alkali activator (LAA) is added to FA, which consists of 50:50 sodium silicates (Na2SiO3) and sodium hydroxide (NaOH) solution by weight. Laboratory investigation includes the determination of volumetric shrinkage strain through image analysis and scanning electron microscopy (SEM) images at 7-, 14-, and 28-days curing period. Results indicate a significant reduction in volumetric shrinkage strains from 56 to 15, 11, and 5%, respectively, with a treatment of expansive soil with LAA/FA = 1, 1.25, and 1.5 at a curing period of 28 days. The SEM images captured to observe the microstructural changes at a 28-days curing period reveal that the right amount of dense crystalline products is formed at an LAA/FA = 1.5. From the analysis, an LAA/FA ratio of 1.25 may be considered as an optimum dosage to control the volumetric shrinkage strain. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd