Hydraulic conductivity of cement-stabilized marine clay with metakaolin and its correlation with pore size distribution

Metakaolin (MK), widely used for high-performance concrete admixtures, is introduced into improving the percolation behaviors of cement-stabilized soft clays, which is a key performance when analyzing the permeability and consolidation in the grounds modified by deep mixing methods etc., the underground water seepage and the migration of pollutants in waterproof curtains by grouting methods etc. To investigate MK effect on the hydraulic conductivity of cement stabilized soils, the flexible wall permeameter was developed and mercury intrusion porosimetry (MIP) tests were performed. The results show that the addition can reduce the hydraulic conductivity 10-100 times when MK content arrives at 3% to 5%, which attributes to less total porosity and pore diameter. As the cement stabilized soils not only belong to a kind of special soils in geotechnical engineering, but also belong to cement-based reinforced materials, it is further discussed whether the unique expression of the hydraulic conductivity of these porous materials (clay, cement stabilized soils, cement pastes and concretes) existed. The results present that there is a good correlation between the hydraulic conductivity, the void ratio and median throat pore diameter for each kind of materials from clays to concretes respectively, and the hydraulic conductivity qualitatively increases with the void ratio and median throat pore diameter whatever clays, cemented soils and pastes or concretes. After several attempts, the combined variable nD502 was adopted to normalize the macro and micro characterization of porosity, and the relatively unique relation depicting the hydraulic conductivity of these materials was proposed.