中国におけるコンクリート廃棄物及びセメント微粉末を利用した塩類土壌改良評価

Abstract

Salt-affected soils are widespread in countries with arid and semiarid regions, and a decrease in agricultural production due to excessive salts is a very serious problem. In China, we have performed a salt-affected soil amelioration with flue gas desulfurization gypsum (FGDG) since 1996. Otherwise, the accelerating urbanization has led to a large number of demolitions of infrastructures in China. Therefore, the need for the recycling and reuse of not only FGDG but also waste concrete (WC) is a pressing issue. In this study, changes in physicochemical properties in the salt-affected soil amelioration with FGDG, cement fine powder (CFP), and waste concrete particles (WCP) were reported. Two high ESP soils in Yinchuan, China were used in the soil amelioration test. The pH and EC values in CFP and WCPs took a higher value than FGDG, and the order of Ca concentration was FGDG > WCP > CFP. In the soil amelioration tests using CFP and WCPs, salt-affected soil decreased drastically in EC and ESP. Moreover, the CFP and WCPs in different particle diameters based on the 1.0 wt% application rate of FGDG were added to the soil. Soil chemical properties before and after mixing with soil amendments were measured, and their properties were evaluated after 3 weeks and 6 weeks. Consequently, soil EC and ESP decreased drastically in all application tests, but soil pH in CFP and WCPs took a high value. And pH, EC, and ESP after 6 weeks took almost the same value immediately after amelioration. WCPs smaller than 2.0 mm could ameliorate a high ESP soil at a lower application rate compared to larger WCPs. In addition, the increase in hydraulic conductivity due to waste concrete application could be confirmed. These results indicated the effectiveness of waste concrete as salt-affected soil amendments.