Mechanisms of Distress Associated with Sulfate Induced Heaving in Lime Treated Soils

摘要

Field observations suggest that ettringite induced swell in lime treated soils maymanifest very rapidly after placement and compaction or after months or even years afterlime treatment. In either case, forensic investigations have identified the presence of themineral ettringite in distressed sections. But the time window between the observation ofdistress and the subsequent forensic evaluations left room for doubt as to whether theettringite caused the observed distress or was formed between the observed distress andthe time of the forensic investigation. The study focuses on identifying alternative,probable mechanisms of swelling when sulfate laden soils are stabilized with lime. Theresearch addresses the hypothesis that swelling in sulfate-bearing fine-grained soils is dueto one or a combination of three separate mechanisms: (1) volumetric expansion duringettringite formation, (2) water movement triggered by a high osmotic suction caused bysulfate salts, and (3) the ability of the ettringite mineral to absorb water and contribute tothe swelling process. The data validate that the synergy of mechanisms discussed hereincontribute to swelling distress. The paper also addresses the impact of matrix strength ofthe stabilized soil on damage potential.