Stiffness Behavior of Soil Stabilized with Alkali-Activated Fly Ash from Small to Large Strains

Abstract

Alkaline activation of fly ash creates a geopolymeric cement that can replace ordinary portland cement in several applications such as soil improvement, with the advantage of much lower carbon dioxide emissions and reusing an industrial by-product otherwise landfilled, which averts several environmental problems. In this paper, the behavior of a silty sand improved by the alkaline activation of fly ash is analyzed from small to large strains by presenting uniaxial and drained triaxial compression test results and seismic wave velocities measured throughout the curing period. The dynamic, cyclic, and static tests showed a significant increase in stiffness with curing time, even beyond the 28-day curing period. On the basis of the nondestructive wave-propagation technique, the increase of the shear and compression wave velocities with time were drawn, giving the evolution of the elastic shear modulus and the Poisson ratio values. The dynamic Young modulus was compared to the correspondent secant Young modulus obtained from the mechanical tests. In addition, the evolution of the properties of this stabilized soil with curing time was compared and confronted to that of soil cement on the basis of the elastic stiffness of both materials, which showed that the most significant difference lies on the curing rate.