Enhancement of engineering characteristics of peaty clay due to mixing with cement

Thick layers of soft peaty clay encountered in recent infrastructure development projects in Sri Lanka had been improved mainly by different techniques of pre-consolidation. Alternatively, if peaty clay is mixed in situ with a binder, such as cement, apozzolonic reaction can be induced causing a fundamental change in microstructure. Greater improvement of strength and stiffness would be achieved more rapidly than with pre-consolidation. Samples of peaty clay obtained from the Southern Transport Development Project were mixed with 15% and 20% of cement by wet weight and the mix was allowed to harden. A surcharge was applied by a special loading arrangement to simulate the overburden pressure under which it will harden in the field. Improvements achieved in strength and stiffness of treated peat were assessed by conducting consolidation tests and unconsolidated undrained triaxial shear tests. The results indicated that significant improvements were achieved in the undrained shear strength and primary and secondary consolidation characteristics. Improvements achieved in secondary consolidation ,characteristics were more significant. Micrographs obtained through Scanning Electron Microscopes (SEM) illustrated the micro structural changes taken place in the peaty clay due to mixing with peat