Distribution of mineralized carbonate and its quantification method in enzyme mediated calcite precipitation technique

This study discusses the possible application of enzyme mediated calcite precipitation, EMCP, as a soil-improvement technique. It explains the experimental works on this EMCP technique. The first part of this paper addresses the different methods for quantifying the amount of calcite precipitated within sand. Two methods, namely, the thermal decomposition method and the CO2 volume evaluation method, are examined. These methods serve to evaluate the calcite distribution within the treated sand. The second part of this paper explains the experimental procedures and the results of drum-can experiments. Homogenous sand specimens, with a diameter of 57 cm and a height of 60 cm, are prepared inside a steel drum-can. A grout solution, comprising urea, urease, and CaCl2, is injected into the centre of the sand specimens. Subsequently, the improved samples within the specimens are collected and their compressive strength is evaluated. The maximum measured unconfined compressive strength is 380 kPa. An attempt is made to relate the improved mechanical properties of EMCP-treated sand to the amount of mineralized carbonate. The obtained calcite-strength relation is found to be in close agreement with the relation obtained in previous literature.