Quantitative analysis of fly ash in hardened cement paste

Fly ash (FA) is one of the common supplementary cementitious materials used in cement and concrete. Because of the complexity of morphology, component, hydration and other factors of FA, it is very difficult to measure the content of FA in hardened concrete. According to the characteristic of the unburned carbon in FA neither dissolving in concrete nor participating in the chemical reaction, three different kinds of FA were used to prepare FA-cement pastes with different volumes. Then selective dissolution method and thermal analysis were used to quantitatively analyze the content of FA in hardened paste. The results indicated that the differences of testing data were less than 1.5%, compared with the theoretical values by the method of selective dissolution combined with thermal analysis. Therefore, it is concluded that the method of selective dissolution combined with the thermal analysis can measure the content of FA in hardened FA-cement system more accurately.