The effects of compaction delay and environmental temperature on the mechanical and hydraulic properties of lime-stabilized extremely high plastic clays

A comprehensive experimental programme was performed with the focus on assessing the effects of compaction delay and ambient temperature on the physical, mechanical and hydraulic properties of lime treated expansive clays. Specimens were mellowed for a period of 0, 3, 6, 12, 24 and 48 h at two different temperatures of 20°C and 40°C prior to being compacted, tested and/or cured for up to 28 days for evaluating the impacts on long-term strength development. All specimens were prepared with the same dry unit weight of 12.16 kN/m3 and moisture content of 40% except for tests aimed at determining dry unit weight as a function of mellowing period. The results revealed that as the mellowing duration increased the dry unit weight declined remarkably at both temperature within the first 12 h. In addition, higher reduction rate was observed when specimens were mellowed at a temperature of 40°C. A 97% reduction in swelling pressure was obtained when the specimens were compacted upon mixing (zero hour mellowing period) and left to cure for 24 h prior to testing. Permeability coefficient of lime treated expansive clays was increased by up to 40 times when compaction was delayed for 24 h or when specimens were mellowed at 40°C. Specimens mellowed at a temperature of 40°C showed relatively stable values of permeability coefficient over the measurement period which could be attributable to accelerated pozzolanic reaction. The Unconfined Compressive Strength tests revealed that strength of lime treated expansive clays is significantly affected by compaction delay. An increase of 234% and 282% in the Unconfined Compressive Strength was achieved after 24 h of mixing with no compaction delay at 20°C and 40°C respectively. Gradual long-term gain in strength was observable within the 28 days post mixing but the rate of strength gain becomes slower and independent of temperature after the first 24 h of mixing. The results suggested that the four key reaction mechanisms occur concurrently with the first 12-24 h after lime addition recognized as being the most crucial period of time. Damaging the cementitious compounds by delayed compaction is harmful to strength and restraining of swelling potential of lime treated expansive clays.