Influence of delayed compaction on the compressibility and hydraulic conductivity of soil-lime mixtures

Conflicting recommendations and opinions can be found in literature concerning the effects of a delayed compaction of lime-stabilized soils. This study was carried out to evaluate such effects on a clayey soil (CH) with 5% of quicklime and hydrated lime. One-dimensional consolidation and hydraulic conductivity tests were carried out on samples compacted soon after lime addition and after 48 h. Analysis of results, helped by scanning electron microscopy and mercury intrusion porosimetry, shows that, for the tested soil, delayed compaction causes a reduction of the dry unit weight up to 11% with hydrated lime and to 18% with quicklime and a greater compressibility of the mixtures at high pressures (at 800 kPa the compression index of samples compacted with delay is doubled relative to that of the immediately compacted ones). However, pozzolanic reaction was found to progress with curing time, even in the case of delayed compaction. The hydraulic conductivity is not significantly modified by a delayed compaction; it is strongly affected by the wetting conditions of curing in the case of hydrated lime. In general, a prompt compaction is always recommendable after addition of hydrated lime whereas the use of quicklime mitigates the influence of a delayed compaction.