Effect of Ionic Stabilization on Vertical Movement in Expansive Subgrade Soils in Texas

Abstract

An important consideration for the successful design of flexible pavement systems in Texas is the prediction and control of the vertical change in height of the subgrade soils due to swelling upon wetting and shrinkage upon drying. The purpose of this study was two-fold. The first objective was to measure the volume change characteristics of clayey subgrade soils from the SH130 corridor in Texas through a suction based approach using the pressure plate. The second goal was to test the effects of treating the soils with the EcSS-3000 chemical stabilizer and lime on controlling the vertical movement and moisture susceptibility.

Recent research studies have indicated that the suction compression index, γh, is the parameter that has the most significant direct influence on the amount of vertical movement taking place in expansive soils. The results indicate a 40-50 % reduction in the average γh values and a similar magnitude of reduction in combined swell and shrink potential.

Further, the resilient modulus (Mr) of representative samples was compared prior to and after treatment separately with 6% hydrated lime and EcSS-3000. The purpose of measuring the Mr of the soils was to analyze the moisture susceptibility of the soils and to study the effects of subgrade stabilization on performance of typical pavement systems against the common distresses using the ME-PDG software tool. Also, the contribution of the expansive soils to pavement roughness was measured in terms of loss of serviceability (ΔPSI) using the measured Mr and vertical movement values. The analysis indicate a significant reduction in drop of Mr values of the lime and EcSS-3000 treated soils and a marked improvement in cracking and subgrade rutting characteristics of the pavements. An average reduction in ΔPSI of the pavements by 0.2 to 0.3 points was observed on the stabilized soils.

This study on expansive subgrades and the associated effects of ionic stabilization have yielded the information necessary as guidance for dealing with relevant engineering problems due to expansive soils.