Time of reactions in a lime treated clayey soil and influence of curing conditions on its microstructure and behaviour

•The paper illustrates a method to monitor soil–lime reactions by pH measurement.•The method allows to properly analyse results of permeability and oedometer tests.•Permeability of soil–lime mixtures decreases with time spent in unsaturated condition.•The compression index resulted much higher in saturated curing conditions.•This behaviour is due to a different microstructure detected by SEM observations.

A research programme has been set up to investigate the sequence of physical and chemical reactions in compacted soil–lime mixtures and their influence on the mechanical and hydraulic performance with time. The paper illustrates a method set up to monitor sequence and development of soil–lime reactions with curing time based on pH measurement. The method was also used, together with SEM observations and chemical analyses, to properly analyse results of hydraulic conductivity and oedometer tests performed on compacted soil–lime samples cured in saturated and unsaturated conditions. It was found that the hydraulic conductivity significantly decreases by increasing the time spent in unsaturated condition and it tends to appreciably reduce with time. In terms of compressibility, higher compression index resulted in saturated curing conditions. These differences were found to be due to a different microstructure. A crystalline, more brittle structure was detected in the case of immediate saturation with an ununiformed distribution in pore size. Unsaturated curing conditions give rise to amorphous, uniformly distributed pozzolanic products, with a more homogeneous pore size distribution.