Performance Evaluation of Cement and Slag Stabilized Expansive Soils

Abstract

Swelling, shrinking, and subsequent low strength of expansive soil poses significant damage to structures if it is considered as foundation or fill material. Recently, the use of cement has become very prevalent in stabilizing these problematic soils owing to its effectiveness. However, the swelling potential of expansive soil is not always adequately resolved by cement. The presence of sulfate salts aggravates the situation impairing the effectiveness of cement, leading to the need to reassess its performance. In this study, the effectiveness of different stabilizers was investigated in stabilizing high-plasticity soil. Two types of soil with variable sulfate content were treated with slag, Type I/II, and Type V Portland cement, and their performances were evaluated based on Atterberg limits, pH, unconfined compression, and volumetric swell tests. A total of 312 samples were prepared for 18 different soil–stabilizer blends tested after 7, 28, and 90 days of curing period. Laboratory test results indicated that strength gain performance was attenuated and swelling potential increased due to the presence of sulfate salts. Adding stabilizers improved the strength of soils by a factor of 4–10 and decreased the swelling potential to < 1%. Atterberg limits decreased initially and then slightly increased with the increase of additive dosages. Additives increased the pH up to a maximum value of 11–12, which could be used as an indicator of target stabilizer addition rate. Finally, slag improved the performance of cement significantly and has proven to be a better option for treating high sulfate expansive soils.

Cement Soil Stabilization as an Improvement Technique for Rail Track Subgrade, and Highway Subbase and Base Courses: A Review

“…For Soil-S, the unconfined compressive strength increases with both increments in percentage cement content (8%, 12% and 16%) of Type V cement and number of curing periods while there was an increment in UCS of sample stabilized with Type I/III cement with increase in the number of curing periods only with 8% and 12% cement contents [14].…”

“…And for Type I/III cement there was a decrease in LL with corresponding increment in PI when 8%, 12% and 16% cement contents were separately added to stabilize samples from Soil-S and Soil-L. While for the Type V cement there was decrease in LL with corresponding decrease in PI when 8%, 12% and 16% cement contents were separately added to stabilize samples from both Soil-S and Soil-L [14].…”

“…Both untreated cases of Soil-S and Soil-L had high volumetric swell potential ranging from 12% to 18%. Addition of stabilizers resulted in a decrease in swelling to below 1% both when Type I/III and Type V cement types were added [14].…”

“…In an untreated state, clay content of soil-L (58%) was found to be higher than that of Soil-S (40%) resulting in a higher plasticity index (PI) of Soil-L (49%). Soil-L had a higher OMC (28%) and lower MDD (14.5 kN/m 3 ) due to its higher clay content at standard proctor compaction energy [14].…”

“…Optimum cement content required for treating an expansive soil is likely to be between 8%-10% as further increase in cement content may not necessarily increase the strength rather it may lead to the impairment of expected performance. Also, addition of cement (Type I/III and Type V) to an expansive soil resulted in a huge decrease in swelling potential to less than 1% [14].…”