Hydraulic conductivity behaviour of expansive soil geopolymer binders

Abstract

Geoenvironmental engineering facilities are required to be robust for effective long-term performance. In the present study, a robust experimental design approach was adopted for the development of expansive soil geopolymer binders for use as barriers in landfill systems. Palm oil fuel ash and quarry fines were used as precursor types (PT). The effects of other factors including precursor content, liquid activator type (LT), ratio of activator to precursor (A/P) and method of preparation were considered, in which compaction was done using British standard light energy. The results obtained show that the crucial factors which affect the soil geopolymer are the LT and A/P based on ANOVA. Two interactions including that between PT and LT and that of PT and A/P were found to be significant but yielded anti-synergistic effects on the hydraulic conductivity. The effect of moisture content on hydraulic conductivity for the two significant factors revealed that the variations in hydraulic conductivity are influenced by micro-level changes at the diffuse double layer, which affects the soil shrink-swell behaviour. Scanning electron microscope (SEM) and image processing of the SEM images using Otsu multi-thresholding and watershed segmentation algorithm correlated changes in the hydraulic conductivity with the pore changes in the soil geopolymer. Moreover, X-ray diffraction and Fourier transform infrared spectroscopy analyses further revealed the nuances, which occurred in the soil due to geopolymerisation.