Alum Sludge-Rice Husk Ash based Geopolymerization for the Improvement of Expansive Clays used in Road Pavements
Résumé
In recent years, geopolymer binders have gained attention as viable alternatives to cement due to their good performance in terms of mechanical strength. This study explores the geopolymerization of expansive clays using Sodium Hydroxide-Sodium Silicate (SHSS) solution as an alkaline activator. Alum Sludge (AS) and Rice Husk Ash (RHA) replaced cement and lime to stabilize expansive clays. AS was used in varying contents of 5%, 10%, 15%, and 20% along with the SHSS solution. The optimum AS dosage considering subgrade and subbase California Bearing Ratio (CBR) as per Kenyan Road Design Manual III (RDM III), and the 28 days cured Unconfined Compressive Strength (UCS) was 15%. The CBR values improved from an RDM III S1 to an S6 subgrade classification in response to the additive and SHSS, the CBR from 2.53% to 95.1%. The optimum content of AS was blended with different RHA contents ranging from 4% to 10% to form an AS-RHA precursor for further geopolymerization. The optimum mix for stabilizing expansive soil was determined based on UCS and CBR tests. The results revealed that the optimal blend was 15% AS and 6% RHA, with a CBR value of 116.3% and UCS of 1834.5 kPa. Additional research is crucial to further enhance the AS-RHA geopolymerization in soil stabilization.
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