Experimental study on improving the durability of underground/underwater structures by mixing impregnating agents into unhardened concrete

Components exposed to soil and water are difficult to maintain during their service life, and have traditionally been designed to ensure greater durability than components exposed to air. However, in recent years, severe damage caused by aging has also been observed in components exposed to soil and water, prompting the development of methods to achieve higher durability. To address this issue, the authors developed a method (mixing method) that enhances the durability of concrete components by mixing sodium silicate-based impregnation materials with fresh concrete. In this study, the flowability, deterioration inhibition effects, and mechanical properties of concrete prepared using the mixing method were experimentally confirmed. The results demonstrated that by controlling the addition of the impregnation material, it is possible to achieve deterioration suppression effects equivalent to or superior to those of conventional methods without significantly reducing the workability or mechanical properties. In addition, an equation for estimating the mechanical properties expressed from the amount of admixture was proposed. Based on the results of this study, it is considered that the mixing method can be applied as a method for maintaining and improving the durability of concrete structures. In order to put this into practical use, it is necessary to conduct experiments under a wider range of conditions to improve the accuracy of estimating the deterioration suppression effect and the characteristics that appear, and to expand the range of applications.