The Effect of Soil Porosity and Geopolymer Viscosity on Spreading Grouting in Weathered Clay Shale

Fly ash geopolymer is a potential material for the stabilisation of clay shale. Therefore, this research determines the effect of soil porosity ( n ), binder activator ratio ( f/a ), and geopolymer viscosity on the injected grout volume ( V i ) and soil-grout column of weathered clay shale. The research was carried out using fly ash as a geopolymer binder, dissolved in Na 2 SiO 3 and NaOH(10M) with an activator ratio of 1:1. The binder activator ratios were 0.50, 0.75, 1.0, and 1.25, with injection applied in the compacted clay shale using three dry densities corresponding to the porosity of 0.42, 0.48, and 0.54. Furthermore, a cylindrical specimen with 46 mm diameter and 100 mm height was used to carry out this test. A hole with a diameter of 12 mm and 80 mm depth was bored at the centre of the specimen to model a fracture grouting method, which was injected with the geopolymer by applying a pressure of 100 kPa for 20 minutes. The research found that the higher the binder activator ratio, the lesser the viscosity obtained; therefore, the grout easily penetrated the pores between the soil particles. As a consequence, more volume of geopolymer could be injected in soil. Binder activator ratio lesser than 0.75 was ineffective for the injection method, and binder activator ration between 1.00 - 1.25 was recommended for the grouting injection method. A new equation to determine the grout diffusion was proposed based on this experiment, as written in the equation ( R i / R b ) n ⋅ f / a = K ( V i / π ⋅ R b 2 ⋅ L ) n ⋅ f / a .