2016 Volume 65 Issue 11 Pages 779-786
The relationship between compressive strength and cement hydration reaction was investigated to clarify the strength evolution mechanism of ultra-high-strength concrete with silica fume and fly ash. Compressive strength of concrete and pore volume of cement paste were measured. In addition, an index of C-S-H volume was estimated based on XRD/Rietveld analysis, thermogravimetric analysis and pozzolanic reaction analysis. As a result, it was recognized that a higher compressive strength was associated with a lower pore volume. Moreover, a lower pore volume was associated with a higher C-S-H volume. Therefore, it can be said that gel pore and capillary pore of cement paste were filled up with C-S-H when concrete with a low water-to-binder ratio received a heat treatment of 70 to 90°C and that a compressive strength of 200 N/mm2-class was caused by the solidity of micro structure in cement paste. With regard to the material characteristics, it was revealed that pozzolanic reactivity of admixture and mineral composition of Portland cement affected compressive strength of ultra-high-strength concrete. In contrast, Blaine specific surface area of Portland cement had little effect on it.
