Reducing the negative impact of freezing and thawing cycles on marl by means of the electrokinetical injection of calcium chloride

The purpose of this study was to compensate the negative impact of freezing and thawing cycles on marly soil by means of electrokinetical injection of calcium chloride as a remediation method. Therefore, firstly, the effect of concentration of CaCl2 solution, voltage gradient, and electrokinetic remediation time on the marl improvement was assessed. The electrokinetic remediation tests were conducted for nine different testing scenarios. As the improvement verification criteria, the unconfined compressive strength (UCS), electric potential difference, and drainage were measured. After performing the electrokinetic remediation test, three sets of UCS samples were taken from around anode, cathode, and the in-between. Instantly after that, the UCS of the first set was measured so that the improvement effect might be determined. Afterwards, one and four cycles of freezing and thawing were applied to the second and third sets of samples, respectively, and the UCS loss was measured. After four cycles of freeze-thaw, the concentration of 1.1 kg/lit, i.e. 1.1 kg of CaCl2 powder was dissolved in 1 lit of distilled water, and remediation period of 4 days for all locations in the sample, and the voltage gradient of 2 V/cm near anode and 1 V/cm near cathode and the in-between areas resulted into the highest UCS. It should be mentioned that in all test scenarios, the samples after four freeze-thaw cycles still had an acceptable value of UCS, whilst the natural marl samples provided for the study were demolished only under a small load after one freeze-thaw cycle. Micro-structural analysis was also performed based on XRD and SEM methods and it affirmed the occurrence of chemical modification and the change of the particles into flocculated particles and consequently the improvement of marl after electrokinetic remediation.