Abstract
This paper presents the test results on the shear performance of large-size reinforced concrete beams using recycled fine aggregate to evaluate its applicability to structural concrete. The performance of these beams is compared to that of similar beams casted with natural coarse and fine aggregates. All of the beam specimens without shear reinforcement had $400mm{\times}600mm$ rectangular cross section and a shear span ratio (a/d) of 5.0. Five concrete mixtures with different replacement levels of recycled fine aggregates (0, 30, 60, 70 and 100%) were used to obtain a nominal concrete compressive strength of 28MPa. The test results of load-deflection curve, shear deformation, diagonal cracking load, crack pattern, ultimate shear strength, and failure mode are examined and compared. In addition, code and empirical equations from KCI, JSCE, CSA, Zsutty, and MCFT were considered to evaluate the applicability of these equations for predicting shear strength of reinforced concrete beam with recycled fine aggregate. The results showed that the overall shear behavior of reinforced concrete beams incorporating less than 60% recycled fine aggregate was comparable with that of conventional concrete beam. The MCFT gave good prediction and other code equations were conservative in predicting the shear strength of the tested beams. The beam specimens with replacement of 70 and 100% of natural fine aggregates by recycled fine aggregates showed different failure mode than other tested beams.
이 연구는 순환잔골재를 사용한 콘크리트의 전단거동을 평가하고자 하였다. 추가적으로 순환굵은골재를 현행규준식 및 제안식과 비교/분석하였다. 동일한 압축강도를 갖는 5개의 실험체를 계획하였으며 각 실험체는 순환잔골재치환율(0%, 30%, 60%, 70%, 100%)을 변수로 계획하였으며 전단철근은 보강하지 않았다. 실험에 사용한 순환잔골재는 흡수율과 비중을 만족하는 골재를 사용하였다. 사용한 골재 중 70% 치환한 실험체의 경우 저품질의 순환잔골재를 사용하였다. 실험은 하중-변위관계, 전단변형, 경사균열하중, 균열패턴, 최대전단강도, 파괴모드를 분석하여 평가하였다. 실험 결과 순환잔골재를 사용한 철근콘크리트 보의 전단거동은 천연골재와 비교하여 전반적으로 큰 차이를 보이지 않았으나, 전단에 관한 규준식 및 제안식과 비교한 결과 순환잔골재를 사용한 철근콘크리트 보의 경우 규준식 수정을 통한 새로운 제안식이 필요할 것으로 판단된다.