FLEXURAL BEHAVIOR OF COMPOSITE REINFORCED CONCRETE ELEMENTS

Although structural light-weight concrete has enjoyed frequent application in Europe and the United States since the 1950s, it has not been used at all in Turkey despite abundant and economical sources of natural light-weight aggregates. The reason for this reluctance is lack of confidence and technical ignorance. In order to allay, to some extent, the fear in the construction sector of using pumice as a concrete aggregate, composite reinforced concrete (CRC) is suggested. The CRC element consists of two layers, the lower being cast as normal-weight concrete (NWC) and the upper as a layer of light-weight concrete (LWC), both of which are placed in the fresh phase, the LWC overlying the NWC. Hence, bond strength will be close to that in normal reinforced concrete elements, which is important for Turkey, where usage of plain steel reinforcement bars is still common. The depth of the LWC layer will be greater than that of the NWC layer. Because of the widespread practice of ready-mixed concrete suppliers, it is practicable for some mixers to carry LWC while others handle NWC. In this study, theoretical ultimate strength analysis of such a CRC element is done and its mechanical behavior is experimentally investigated by subjecting many prototype CRC elements to bending in a conventional four-point loading-frame setup. It is observed that the CRC elements behave similar to normal reinforced concrete elements with the advantage of reduction in dead weight.