| Summary: | 碩士 === 中原大學 === 土木工程研究所 === 99 === In this research, recycled concretes are made according to field mix design used in ready-mixed concrete plant with discarded concrete blocks (as coarse aggregates) and discarded tiles (as fine aggregates). Moreover, the ratio of cement and pozzolanic admixture (fly ashes and stove stones) within recycled aggregates specimens are adjusted as well. Meanwhile, the water to binder ratio of pozzolanic admixture does not increased for more than 25%. Slump test according to ASTM C143, chloride experiment, compressive strength test, supersonic wave experiment, and high temperature test are carried out in the same environment and allocated percentages, and the differences between recycled concretes and natural fine aggregate concretes are studied.
Results of the tests show that the early reaction of recycled fine aggregate concrete is faster than nature fine aggregate concrete. No matter what percentage of water to binder ratio, the strength of recycled fine aggregate concrete is higher than natural fine aggregate concrete. While talking about the strength, there is not much difference in the age of 7-days recycled fine aggregate concretes with different percentage of water to binder ratios; however, there are significant differences in the later period. In the early age, the differences between the strength of recycled fine aggregate concrete added with pozzolanic admixture materials and the strength of concrete which made by recycled pure fine aggregate cement is within 10%. Besides, recycled concretes which made by certain percentage of stove stones and fly ashes is higher than recycled concretes made by pure cements for about 6%. The development of 28-days recycled concretes is gradually slow; but the development of recycled fine aggregate concretes with no pozzolanic admixture is more slower. Nevertheless, the strength of nature fine aggregate concretes increased with certain percentage after 14 days of age. In the later stage for about 91 days, the rest of the recycled concretes reach 90% strength of nature concretes, excluding the recycled concretes made by stove stones and ashes. It is known that the pozzolanic admixture materials not only has significant influence upon the strength of nature fine aggregate concretes, but also do help the specimens made by recycled tiles.
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