Alite-C<sub>3</sub>A-Gypsum系の水和反応における相互作用機構の解明

Abstract

For understanding the cement hydration composed of high C₃A content, pure clinker phases such as Alite, Tricalcium aluminate (C₃A) were synthesized and five different compositions of mixtures were prepared. The hydration of samples were followed by calorimetry. Quantitation of the crystalline and amorphous products were conducted by X-ray diffraction and Rietveld analysis. It was found that the hydration between C₃A and Gypsum was accelerated by hydration of Alite. It was implied that amorphous materials produced from the hydration between C₃A and Gypsum as well as the hydration of Alite. Rise of pH due to precipitation of portlandite from Alite hydration accelerated the hydration between C₃A and Gypsum. It could be explained on the basis of thermodynamic equilibrium theory that AFm phase with low sulfate content precipitated in the vicinity of C₃A particle. In the bulk solution far from the surface of C₃A, AFt with high sulfate content precipitated. Subsequently, because of low sulfate content in AFm, mass transfer into C₃A particle kept proceeding and hydrating C₃A continuously progressed. That is why hydration reaction of C₃A proceeds when added Alite in contrast to the hydration without Alite.C₃A含有量の多いセメントの水和反応について理解することを目的とし、その主たる反応を司るAlite、C₃A、Gypsumを混合したモデルセメントの水和実験を行った。発熱量測定、XRD・リートベルト解析、TG-DTA測定の結果、Aliteの水和反応がC₃A-Gypsum系の水和反応を促進させることを確認した。さらに、その要因はAliteの水和反応からPortlanditeが生成することによるpH上昇であり、その際C₃A粒子付近に析出するAFm相に含まれるSO₄²⁻量が少ないため、未水和C₃Aへの物質の透過が継続するからであることが示唆された。