Abstract
Coral sand includes a lot of calcium carbonate. Colloidal silica contains phosphoric acid as a reactive material. Calcium carbonate reacts the chemistry with phosphoric acid included in colloidal silica, and carbon dioxide is generated. There were two problems by occasion of these. The first problem is that bubble with carbon dioxide remains in the improved sand, and strength of improved sand is not obtained. The second problem is that gel time shortens extremely and the grouting of colloidal silica into the ground becomes difficult. This paper describes the results of the laboratory tests of improved sand made by using coral sand, and the results of grouting test in coral sand ground. The laboratory tests have been conducted on improved sand such as unconfined compression and cyclic torsional tests. From the test results, it was found that: 1) improved sand by permeation grouting under constant confining pressure doesn't remain the bubble, and have enough strength; 2) colloidal silica can be grouting into the coral sand ground by colloidal silica gel time slows while flowing.
