The Effects of RHA Dosage on Compressibility and Microstructural Development of Stabilized Calcite-Rich River Sludge

The maintenance and construction operations along riverways often lead to large amounts of river sludge that can cause severe environmental pollution problems if not disposed of properly. To reduce the risk of such environmental concerns, alternative handling methods such as stabilizing the river sludge are effective in improving the geotechnical properties of such wastes, making them useful in the construction industry. This study aims to chemically stabilize river sludge using control-burnt rice husk ash with high amorphous silica content. The study experimentally investigated the effects of different rice husk ash dosages on the compressive strength (qu), modulus of deformation (E50), microstructural developments, and the ultimate chemical compositions in the stabilized river sludge specimens during the curing period. The methods applied in this study to reveal the intrinsic mechanisms included an unconfined compressive strength test, scanning electron microscopy test (SEM), and X-ray powder diffraction (XRD). The results showed maximum peaks of calcium aluminosilicate hydrates gels (CAH-gels) at 5%RHA, a pozzolanic reaction product, which formed strong cementation bonds in the river sludge-RHA composite. Identifying CSH gels and the firmly cemented microstructure provided an insightful interpretation of the structural and strength evolution of RHA-stabilized river sludge. This proposed stabilization methodology proved to be an essential parameter in solving the uncontrolled disposal of river sludge and as a conservation measure in saving RHA and river sludge disposal costs.