Hydraulic conductivity variation in compacted bentonite–fly ash mixes under constant-volume and free-swelling flow conditions

Compacted bentonite–sand (B–S) and bentonite–fly ash (B–FA) are established combinations for the construction of landfill liners. This study determined upper lower bounds equilibrium hydraulic conductivity (k eq ) amended B under extended duration flow. The k constant-volume flow condition differed from free-swelling by more than two orders magnitude due to difference in geomaterial interaction, microstructural changes, mineralization. Considering condition, B–FA mix with class F C fulfilled criterion up 70% 30% amendment, respectively. higher observed mixed FA was attributed formation porous calcium aluminium silicate hydrate gel ettringite needle type minerals. time taken achieve inversely related a power relationship. data this were used propose empirical relationships estimating (long-term) based on obtained at 48 hours (short-term), plasticity type. reveals that can be as an alternate S amendment material, should designing liner.