Stabilization of an Expansive Soil Using Alkali Activated Fly Ash Based Geopolymer

Expansive soil is one of the most devastation types of soil damaging roads, building, and pipe line each year. Various efforts are being done to stabilize the soil and mitigate the damage due to it. Utilization of industrial waste as low CO₂ cement is one of the sustainable method for industrial growth. In the present study alkali activated fly ash used as an alternating cementitious material to stabilize an Indian expansive soil. Different combination of sodium hydroxide and sodium silicate were used in terms of Na₂/SiO₂ ratio. The activator to ash ratios (liquid to solid mass ratio) was also varied with different percentage of class F fly ash percentage. The fly ash is activated with 10, 12.5 and 15 molal of sodium hydroxide concentrations of along with 1 molar sodium silicate solution. The various percentages fly ash (20, 30 and 40%) relatively to the total solids of the expansive soil are used. The activator to ash ratios (liquid to solid mass ratio) was kept between 1 and 2.5. The effectiveness of this binder is discussed in terms of unconfined compressive strength (UCS) of the stabilized soil after 3, 7 and 28 days of curing. The effect of alkali activation is discussed in terms of stabilization of expansive soil with only fly ash. The mineralogical development of the stabilized expansive soil is discussed through x-ray diffraction analysis. The effect of activator to ash ratio is also discussed. Suitability of alkaline activated fly ash mixture as a grouting material is also ascertained by studying the rheological properties of the grout such as, setting time, density and viscosity and is compared with that of common cement grouts.