Abstract
The energy dissipation capacity of concrete is an important aspect for a Reinforced Concrete (RC) structure to be seismically resistant. Various types of concrete incorporating sustainable materials are being developed these days such as recycled aggregate concrete. Determination of energy dissipation capacity of such new types of concrete is of great importance for their application in RC structures which are to be constructed in seismically active areas. In this regard, the experimental study presented in this contribution investigated the energy dissipation capacity of RC beams constructed using recycled aggregate concrete and subjected to three different deflection amplitude levels of reverse cyclic flexural loading. For this purpose, a total of 20 RC beams of cross section 75 x 150 mm and length of 1350 mm were cast using five different concrete compositions and tested. Among five different concrete compositions, one was control concrete containing 100% natural aggregates while the remaining four compositions were of recycled aggregate concrete containing natural and recycled aggregates. Four replacement levels (25%, 50%, 75%, and 100%) of natural aggregates with recycled aggregates were examined. Results indicated that the amplitude level of imposed deflection is an important factor which influenced the value of energy dissipated by RC beams. Further, results showed that RC beam constructed using recycled aggregate concrete containing 25% recycled aggregates exhibited energy dissipation capacity similar to or even better than that of control RC beam containing 100% natural aggregates.
Highlights
In many countries, rapid development, modernization, and industrialization in recent years have generated large amounts of debris in the form of Construction and Demolition (C&D) waste
The data were in the form of hysteresis loops for 10 cycles of loading. These hysteresis loops of all 3 amplitude levels (4mm, 5mm & 6mm) for the five compositions of concrete investigated in this study are shown in Fig.7 to Fig.9, where it can be noticed that the hysteresis loops of Natural Aggregate Concrete (NAC) and all classes of Recycled Aggregate Concrete (RAC) are almost identical
The cracking patterns of beams subjected to reverse cyclic flexural loading of amplitude 4mm, 5mm and 6mm are shown in Fig.10, where it can be seen that similar to hysteresis loops there is no major difference in the cracking of Reinforced Concrete (RC) beams containing Recycled Aggregates (RA) at different percentage levels and 100% Natural Aggregates (NA) in terms of the number of cracks and crack spacing
Summary
Rapid development, modernization, and industrialization in recent years have generated large amounts of debris in the form of Construction and Demolition (C&D) waste. A major aspect of the structural performance of concrete in seismically active regions is its ability to adequately dissipate the energy when subjected to cyclic loading. The study parameters included replacement level of NA with RA and steel ratio and yield strength of spiral reinforcement They found that cylindrical specimens constructed using RAC and confined by spiral reinforcement exhibited structural performance similar to that of NAC specimens. The findings of research studies [16,17,18] carried out in the recent past to investigate the mechanical performance of RC structural members constructed using RAC and subjected to cyclic or seismic loadings have revealed that the energy dissipation capacity and ductility is degraded by replacing the NA with RA; but still RAC fulfills the related requirements of earthquake resistance designing. Since many areas in Pakistan are susceptible to earthquake loading; the outcome of such experimental studies could be important and useful to devise recommendations regarding the application of RAC in real RC structures in seismically active regions
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