چكيده به لاتين
Abstract
Reactive powder concrete (RPC) is an ultra-high performance concrete developed in 1994 by Richard and Cheyrezy through particle packing technique. In this approach, with the elimination of coarse aggregate and microstructure engineering of the composite matrix, a concrete with unique properties including a very high mechanical strength with a highly dense microstructure has been introduced. The unit weight of RPC, however, is normally 2150–3000 kg/m3 and this increases the dead load of the structure and undoubtedly the costs. In this study, the production of lightweight reactive powder concrete (LRPC) was aimed by using GGBFS to totally replace the quartz powder and incorporating Expanded polystyrene (EPS) beads, Modified Expanded polystyrene beads (MEPS), Polystyrene (PS) powder and solvent recycled-polystyrene powder (SRPS) at different replacement levels of 15%, 30% and 45% (by volume of binder paste). The obtained results show that incorporation of EPS beads into RPC and increasing its replacement level results in significant reduction in concrete compressive strength (60-80%) due to loss of integrity caused by weak mechanical nature of beads and their very low density and also concrete inefficient compaction. In the next step, the application of heat to increase the mechanical strength of EPS beads by upgrading their microstructure and producing LRPC by using MEPS was considered. A 60% improvement is observed in terms of physical and mechanical properties of LRPC when MEPS aggregate is replaced with RPC paste. In the 3rd and 4th stages, increasing the uniformity of LRPC and preventing high loss of mechanical strength by significantly reducing the maximum size of EPS beads or using PS and SRPS was considered. Using PS and SRPS at replacement levels of 15%, 30% and 45% resulted in achievement of densities of 2020, 1820 and 1650 kg/m3 with noticeably lower losses of 5.3%, 8.6% and 28% in compressive strength, respectively. Based on the obtained results, at the same density, the LRPC containing PS shows 43% and 150% higher compressive strengths compared to LRPCs containing MEPS and EPS, respectively.
Keywords: Light Weight Concrete, Reactive Powder Concrete, Expanded Polystyrene, Ground granulated blast furnace slag
