A method of quantitative determination of granulated blastfurnace slag not only in unhydrated slag cement but also in hydrated paste as an unreacted part was established by using a salicylic acid, aceton-methanol solution. In this solution slag hardly dissolves, but most of the hydrated slag, clinker minerals and their hydrates dissolve. Utilizing this principle, with some corrections if necessary, it is possible to determine the amount of unreacted slag.
The experiment to determine the amount of unhydrated slag on the hydration of various types of slag cement pastes were carried out.
The amount of unreacted slag contained in these cement pastes was determined by using the salicylic acid, aceton-methanol solution. The accuracy of this measurement was found to be satisfactory. Unreacted C₃S was quantified and the hydration products were detected by X-ray diffraction. Non-evaporable water, free Ca(OH)₂, and free CaSO₄ were also determined by chemical analysis, and the hydrated phases were observed under a microscope.
The chemical compositions of the products and the rate of reaction of each component such as slag, C₃S and CaSO₄, and the depths of the reacted layer on the particles of slag and C₃S were calculated from the experimental data.
In every type of slag cement, the rate of reaction of slag contained was unexpectedly slow. Further, after hydration for about 3-7 days, the rate of reaction of slag and C₃S showed a remarkable decrease.