Stabilization of peat soil using cement and Rice Husk Ash: strength and microstructural evaluation

Peat soil is a highly compressible and weak geomaterial with high water content and low shear strength, making it unsuitable for the support of engineering structures without stabilization. This study investigates the effectiveness of Ordinary Portland Cement (OPC) and Rice Husk Ash (RHA) for enhancement of engineering and strength properties of peat collected from Ziro Valley, Arunachal Pradesh, India. Different percentage OPC and RHA were used to treat the peat soil and the effects of the percentage of the binder and curing periods on the compaction characteristics and Unconfined Compressive Strength (UCS) were investigated. Standard Proctor compaction and UCS tests were performed after 0, 7, 14 and 28 days curing. The results showed that the strength of peat soil significantly increased as a function of both the amount of OPC and RHA added to the soil, and the curing time. The optimum mixture of 15% OPC + 12% RHA resulted in the highest UCS value of 819 kPa, an improvement of 333% from the value of 189 kPa of the untreated peat soil. The microstructural analysis also revealed the improvement in strength, as SEM images displayed a more compact and cohesive soil matrix after stabilization, fewer pore spaces and stronger bonding between particles. XRD analysis determined the mineral phases of silica bearing minerals and other mineral phases related to RHA and stabilized soil matrix. The main findings of this research are that the use of OPC and RHA concurrently can significantly improve the strength and microstructural properties of peat soil, indicating its potential as a stabilization of weak organic soils, and the use of RHA as an agricultural by-product.