The development of new magnesium phosphate cement containing the calcinated dolomite and the immobilization of Pb by hardened new cement

• Project/Area Number: 15K06161
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Civil engineering materials/Construction/Construction management
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Sakai Etsuo 東京工業大学, 物質理工学院, 特任教授 (90126277)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Project Status: Completed (Fiscal Year 2017)
• Budget Amount: ¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000); Fiscal Year 2017: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2016: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2015: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
• Keywords: リン酸マグネシアセメント / ドロマイト / 半焼成ドロマイト / 低アルカリセメント / 重金属固定 / 硬焼マグネシア / リン酸二水素カリウム / 硬化機構 / マグネシアリン酸塩セメント / 酸塩基反応 / 低アルカリ / 重金属固定化 / 資源有効利用 / リン酸セメント / 重金属固化

Outline of Final Research Achievements

This paper is describes the new magnesium phosphate cement containing the calcinated dolomite at 700℃. The calcinated dolomite consists with MgO and CaCO3. New cement is in MgO/CaCO3-KH2PO4-H2O system(DK cement). This paper discusses the hardening mechanisms and the reaction products of the DK cement compared with the ordinary phosphate cement having hard burned MgO（this is abbreviated MK cement）. The main reaction product in both DK and MK cement is KMgPO4・6H2O.In DK cement, a small amount of CaK3H(PO4)2 is also formed. Unreacted MgO and CaCO3 are remained in hardened DK cement and unreacted MgO is only remained in hardened MK cement. pH of hardened DK cement is lower than that of ordinary Portland cement and is less than 12.5. The dissolution of Pb ions from hardened MK or DK samples containing Pb ions is less than the environmental quality standards for soil. This is related to the relationship between the solubility of Pb(OH)2 and pH of liquid phase in cement.