The unsoaked and soaked strength soft hes tabilized clay samples for different FA contents at the OWC are shown in
Figs. 5, 6 and 7 for the active, inertand deterioration zones, respectively. In the active zone, FA slightly improves
strengths. Strength development in the inert zone is essentially dependent on the FA content. The strength increases sharply as the FA content increases up to the optimal value and then decreases as the FA content decreases. For a short curing time (o7 days), the optimal FA content is at 15%; for along curing time (428 days), it is 21%. In the deterioration zone (vide Fig. 1), the strength of CCR stabilized clay is lower than that in the inertzone. There duction in strength with increasing CCR content is caused by unsoundness due to the free lime content. That FA can improve this detrimental effect as indicated by the increase in strength with increasing FA content, as seen in Fig. 7. However,the strength increase is gradual up to an optimal FA content at about 12% for 7 days of curing and about 21% for longer curing times. Even with low FSR, this compacted silty clay is collapsible when the water content increases and thush as the capacity to cause damage to a superstructure (Horpibulsuketal.,2008). The soaked strength of this compacted clay is null. Consequently, both the unsoaked and soaked strengths are important for the
design of earth structures. For the three improvement zones, the soaked strengths are lower than the unsoaked strengths for all curing times (vide Figs. 5 to 7).