Cementation of Soil Due to Carbonate Production in the Presence of Oyster Shell

There is a growing concern socially for the recycling of wastes, and in the geotechnical engineering community ground improvement by reusing wastes is expected to be developed. In the present study, laboratory tests have been conducted to examine the cementation of soil due to carbonate production in the presence of oyster shell with expected metabolic activity of microorganisms. Toyoura standard sand and marine clay sediment were used as soil samples. The soil samples were mixed with buffer solution and the oyster shell in test tubes, and were shaken for 24 h, and then commercial yeast and glucose were added to the soil samples. Changes in the calcium ion concentration and pH with time for the prepared soil suspension were recorded and how the soil samples were solidified was visually observed. The calcium concentration in the solution decreased rapidly and reached a constant value after 12 h, which indicates that the calcium in the liquid phase of the soil samples was precipitated as carbonate. Similar treatment for soil cementation was given to the paste of the standard sand and the marine clay; the specimen of the sand and marine clay cured for 5 days gained the strength of about 14 and 9 times higher, respectively, compared with the specimen cured for 0 days. These results indicate that the cementation using waste oyster shell has the potential of being used for ground improvement when considering waste recycling.