EFFICACY OF ROAD BOND AND CONDOR AS SOIL STABILIZERS (FHWA-OK-13-06 2242)

Abstract

The Oklahoma Department of Transportation (ODOT) uses lime-based stabilizers including quick lime, hydrated lime, Class C fly ash (CFA) and cement kiln dust (CKD) to increase bearing capacity of fine-grained subgrade soils within the state of Oklahoma. Lime, CFA, and CKD have been successfully used as soil stabilizers; however, lime-based stabilizers may react negatively when mixed with sulfate bearing soils which are prevalent in Oklahoma. In an effort to remedy the issues with sulfate bearing and non-sulfate bearing soils, multiple companies have developed alternative additives to the commonly used lime-based additives. Two companies, Earth Science Products and C.S.S Technology, Inc. have produced the acid based chemical additives Condor SS and Roadbond EN 1, respectively. The goal of this research was to determine how Condor SS and Roadbond EN 1 perform relative to lime and fly ash additives in sulfate and non-sulfate bearing clayey soils found within the state of Oklahoma. The approach for this project was to test the two aforementioned chemical additives against lime and fly ash additives according to the test methods outlined in ASTM D 4609 with three different soils from Oklahoma, one of which contained significant levels of soluble sulfate. The main test used to evaluate the two chemical stabilizers was the unconfined compression test (UCT) to evaluate strength gains from the stabilizer and free swell oedometer test to gauge whether chemical addition decreased swelling potential or swelling pressure. Roadbond EN1 and Condor SS did not substantially increase the unconfined compressive strength (UCS) of any of the soils tested nor meet the requirements of ASTM D 4609 per OHD L-50. Roadbond EN1 and Condor SS did not appear to have a significant effect on the liquid limit, plastic limit, or plasticity index of any of the soils tested. The swelling potential of the soils tested were not reduced by the addition of Roadbond EN1 or Condor SS. While increases in UCS were not substantial, there was some noted improvement in the 28-day UCS in the sulfate bearing soil with Roadbond EN1 and Condor SS. In addition, these additives did not produce adverse swelling reactions as noted for fly ash and lime in this soil.