Content of research

To develop a new grout with low environmental load, we focused on minerals produced by living organisms in nature (biominerals), especially CPC, a major component of teeth and bones, and investigated the optimum conditions for CPC precipitation. We also conducted uniaxial compression tests on sand specimens solidified with CPC. In the CPC precipitation test, we have found that the precipitation volume tends to increase as the pH increases from weakly acidic to near neutral. This causes the uniaxial compressive strength of the CPC-solidified sand specimens to reach about 90 kPa, which is within the target range of 50 to 100 kPa for uniaxial compressive strength of sandy soil to prevent liquefaction. Electron microscopy of the specimens showed whisker-like CPC crystals (Fig. 1). These results indicate two possibilities of their usage: chemical grout using self-hardening property and biogrout using pH-dependent precipitation volume.

Potential for social implementation

• ・Countermeasures for liquefaction of sandy soil during earthquakes
• ・Self-restoring concrete and rock
• ・Restoration and conservation of cultural stone properties
• ・Solidification and reuse of the bottom mud of reservoirs
• ・Concrete and rock fracture filling
• ・Insolubilization treatment of contaminated soil

Appealing points to industry and local governments

Previous studies in medicine and dentistry have clarified that CPC has unique physicochemical characteristics. With a little creativity and ideas, CPC may show many advantages, even when it is used as a ground injection engineering material. For example, CPC has a self-hardening property, and its strength increases with the passage of time. In addition, after CPC injection, the ground does not become industrial waste but can be reused as a resource.