نوع مقاله : یادداشت فنی
نویسندگان
دانشکده مهندسی عمران، دانشگاه فردوسی مشهد
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
With the increase in using congested reinforcements in moment-resisting reinforced concrete structures, there is a growing interest in specifying high workability concrete. Self-consolidating concrete (SCC) in the fresh state is known for its excellent deformability, high resistance to segregation, and its use, without applying vibration, in congested reinforced concrete structures characterized by difficult casting conditions. The reuse of aggregates from demolished concrete structures was introduced into practice many years ago and, from the beginning, was mainly considered for two environmental aspects: solving the increasing waste storage problem and the protection of limited natural sources of aggregate. At present, plenty of demolished reinforced concrete or prestressed-concrete structures, originally erected from concrete of moderate or high strength, create a significant source of rubble aggregate of relatively good quality.This paper presents the results of an investigation dealing with the bond strength between steel reinforcing bars and self-consolidating concrete (SCC) made with recycled aggregates. Eight concrete mixtures, in two groups of SCC and normal concrete (NC), were considered. Each group comprised four concrete mixtures with different percentages of recycled aggregates (0%, 30%, 50% and 100%). Sixteen concrete specimens, grouped in two series, made of NC and SCC,were anufactured and tested. In each specimen, four steel bars were embedded in the concrete at the bottom and top of the specimen. The effect of bar position in concrete has been studied by comparing the bond strength of top and bottom bars. The bond strength and slip of each reinforcing bar were measured in a pull-out test setup. The test setup comprised a hydraulic jack, a load sell, a LVDT and a computer aided data acquisition system. The LVDT measured the slip of the reinforcing bar in the concrete specimen. In each test, load was increased slowly with an approximate rate of 25 kN/min, until the bond failure of the reinforcing bar from the concrete. The type of bond failure was by splitting for all specimens. Test results showed that the use of recycled aggregates may not reduce the bond strength in SCC. However, for the case of NC, the recycled aggregates decreased the bond strength. Also, the effect of top bar in SCC is smaller than that in NC.
کلیدواژهها [English]
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