Peat soil is one of the softest types of soil. Various methods have been used in the past to strengthen peat soil deposits. In this research, unconfined compressive strength (UCS) of peat soil was studied while the peat soil was in its undisturbed state, stabilized with ordinary Portland cement, and mixed with polypropylene fibers. Unconfined compressive strength for either stabilized peat with polypropylene fibers or peat without polypropylene fibers was studied at different curing ages from immediately after molding (zero day) to 7, 28, 90, and 180 days. All samples were cured in air, and the procedure includes leaving the stabilized peat soil in normal room temperature and in air throughout the curing period. The curing procedure used to strengthen the peat soils shows that UCS values of stabilized peat soil were considerably increased through the curing process. As the curing time for the stabilized peat soil continues, the moisture contents of the UCS samples are reduced (through evaporation), and therefore the weight of water divided by the weight of cement (W/C) of stabilized samples is reduced. As W/C for samples reduces, the stabilized samples gain strength throughout the curing time. The strength gain continues beyond 28 days which is usual for concrete mixes. The UCS values for the stabilized peat soil show that the strength increases continues through six months of curing period. Addition of polypropylene fibers to the mixture of peat and ordinary Portland cement as a non-reactive additive not only increases the UCS values of stabilized peat soil, but also contributes a considerable amount of uniformity and intactness to the stabilized peat soil samples as well.
