Investigation of Water-Retention Characteristics of Alkali-Activated Clay-Fly Ash Using Small Geotechnical Centrifuge

Abstract

In chemically treated soils, producing binding gels changes the soil structure and pore-size distribution, consequently affecting the treated soil-water-retention characteristics. Alkali-activated materials have recently gained popularity to be used as a sustainable chemical binder for soil stabilization. This study was aimed at investing how alkaline activation changes the water-retention characteristics of a treated clay using a small-scale centrifuge at low suction level by drying process in experimental conditions. Alkali-activated clay-fly ash was fabricated by mixing 60% fly ash and 40% clay then the mixture was activated by 10 M NaOH solutions. A small geotechnical centrifuging setup was utilized so as to estimate the variation of water content due to the suction-induced drying process. It was observed that the saturation degree fell in the ranges of 62.9%–78.3% and 71.8%–87.8% for the untreated and treated clay, respectively. The centrifuging results were verified against some distinguished available models. The water-retention characteristics of alkali-activated clay-fly ash were found to be substantially different from that of the untreated clay. Indeed, for the treated clay, the lower air-entry value suction and higher water-retention tendency for higher suction levels are controlled by its larger mean pore diameter and higher specific surface, respectively. Additionally, flocculated fabric produced due to alkaline activation contains small clusters with water entrapment potential needing tremendous suction pressures to be drained.