| Summary: | 博士 === 國立中興大學 === 土木工程學系 === 92 === There are a lot of influence factors for the concrete strength. When consider a unique factor for the predition of strength, the water to cement ratio proposed by Abrams in 1911 is mostly committed to the practice. In this research it is found that the Abram’s formula can be improved when the capillary porosity was considered as a parameter in the formula.
Since the pozzolanic materials added in concrete don’t have the adhesive ability at early age, the cement amount will control the concretes strength and ultrasonic pulse velocity. In other words, the early age strength and the velocity are affected by the ratio of cement replaced by the pozzolanic material. This research investigate the effects of pozzolanic material on the strength and the ultrasonic pulse velocity of concrete by using three water to binder ratios, three replacement ratios of fly ash and furnace slag, and ten distinct ages from 0.5 ~ 90 days of concrete.
Test results show that, keeping water to binder ratio the same, the larger substitution ratio of fly ash and the furnace slag, the lower early age strength of concrete was found due to the less hydration products of C-S-H. Also the larger amount of cement replaced by the pozzolan materials, the lower pulse velocity was found attributed to the less pozzolanic reaction and a looser interface of pozzolan particles. Base on the above results, a modified model that is more precise to predict the early age strength and pulse velocity of pozzolanic concrete was proposed by extra introducing the factor of pozzolanic material amount in the conventional prediction model.
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