Cement and lime soil stabilizers are becoming more commonplace in the construction of road and pavement systems throughout North American. Greater knowledge about problematic soil chemistry, however, can help avoid costly road and pavement failures that can occur when these two calcium-based stabilizers are used inappropriately. Relatively inexpensive soil tests conducted prior to construction can identify the presence of soil components that will counteract the ability of calcium- based stabilizers to harden the soil. Even worse, their use will generate a heaving phenomenon in the treated soils that will buckle and crack the pavement above and create significant roughness in the running surface. Known as sulfate heave or sulfate-induced heave, pavement damage can be significant. For example, the Dallas District of the Texas Department of Transportation (TxDOT) discovered that application of cement and lime stabilizers to soils containing soluble sulfates resulted in pavement failures costing the district approximately $23 million annually. This did not include the cost for the highway pavement failures being experienced by other TxDOT districts or the pavement failures experienced by the local counties, cities and private industries on their roads and streets. Soluble sulfate chemistry may be present in soils at locations throughout North America. TxDOT, as one of the largest users of cement and lime for soil stabilization, has determined that soils with sulfate content as high as 3,000 to 8,000 parts per million (ppm) can be effectively stabilized by using more costly double application procedures and higher application rates of lime stabilizer products. They have also determined that 8,000 ppm is the upper tolerance for sulfate content, above which the use of cement or lime treatment is not permitted.

Organic content in soils is an even more widespread concern when the use of cement or lime are being considered for soil stabilization as a relatively small amount of organic content in the soil can retard or inactivate their pozzolanic reactions that otherwise would be expected to harden and strengthen the soil. The deleterious effect of the organic materials on the stabilization process also leaves the weakened cement and lime treatments subject to leaching and thus reverse any benefits they might have provided. When the treated soils fail to achieve the strength and stiffness values anticipated in the project engineer’s design, the entire pavement structural section is at risk of premature failure. One percent organic content has long been the upper tolerance for soils considered to be suitable for treatment with cement or lime stabilizers, and this upper limit for organic content has also been incorporated in TxDOT’s guidelines.

The good news is that a concentrated liquid chemical stabilizer has proven effective as an alternative to calcium-based cement and lime stabilizer products. The EMC SQUARED System stabilizer products are non-calcium based and they eliminate the risk of pavement heaving and cracking generated by the addition of calcium-based chemicals to sulfate-bearing subgrade soils. Additionally, rather than being weakened or inactivated by organic content like cement and lime that puts pavement systems at risk of premature failure, EMC SQUARED System treatments mobilize organic content as a positive contribution to the stabilization process. More info here.

LESSONS TO BE LEARNED: When cement or lime treatment are being considered for soil stabilization applications, confirm that the project geotechnical report includes test results for sulfate and organic content. If sulfate or organic content exceed the upper tolerances for use of calcium-based additives, then the EMC SQUARED System stabilization products are proven effective in laboratory testing and time-tested in service for roads, streets, and highways.