Abstract
We examined the characteristics of free lime-hydraulic compound-anhydrite system expansive additive. The clinker structure of free lime-anhydrite expansive additive without hydraulic compound was rough. On the other hand, the clinker structure of free lime-hydraulic compound-anhydrite expansive additive was compact. In addition, the free lime crystal grew large. Compared with the free lime-anhydrite expansive additive without hydraulic compound, the free lime-hydraulic compound-anhydrite expansive additive was excellent in expansion characteristic. Thus, it was clarified that the hydraulic compound played a role to improve expansion performance. It was inferred that the cause of the above phenomenon was deeply related to the structure formation of expansive additive clinker due to the presence of the hydraulic compound. In other words, the presence of the hydraulic compound made the structure of expansive additive clinker compact, and assisted free lime crystal to grow very large, which suppressed the reaction of free lime. we examined also the influence of the preparation method of free lime-hydraulic compound-anhydrite system expansive additive on its performance. The result showed that even thosugh the same composition of additives were used, the expansive additive that was prepared by dispersing the above three compounds into clinker had more excellent expansion performance than the expansive additive that was prepared by mixing the same three compounds. It was considered that these phenomena were originated from differences in the reaction velocity of free lime and formation mechanism of ettringite.
