Study on the workability, mechanical property and water absorption of reactive powder concrete

In order to investigate the influence of various factors on working performance, mechanical properties and durability of sustainable Reactive Powder Concrete (RPC), and make it convenient for choose more cost-effective RPC incorporating industrial byproducts. The effective parameters (water-binder ratio, contents of water reducer, replacement ratios of fly ash (FA), silica fume (SF) and slag powder (SL)) of RPCs were examined by the tests of paste fluidity, compressive and flexural strength as well as water absorption. Besides, the effect of the active mineral admixtures on pore size distribution and surface morphology of RPCs was studied by Mercury Injection Porosimeter (MIP) and Scanning electron microscope (SEM). Results indicate that an obvious reduction in the workability of RPC, enhancement of strength, and reduction in water absorption can be achieved by substituting part of the cement with silica fume. Fly ash and slag powder can be used to substitute some cement in producing RPC, and the workability is improved, meanwhile the effect of fly ash is higher than that of slag powder. However, excessive replacement of cement with slag powder or fly ash leads to a reduction of the strength in the early stage and a greater absorption of water. Increment of curing age is associated with an enhancement of strength and a decrease in water absorption. The porosity is reduced by 5.2% when cement is partially replaced with silica fume, and the microstructure is dominated by harmless pores. When replacement of silica fume is kept at 25%, using slag powder or fly ash substitute part of cement also reduces the number of less harmful pores. It is beneficial to add slag powder to increase the number of gel pores, whereas fly ash reduces the number of gel pores. RPC can achieve a high strength, low water absorption, and improved economy and environmental protection when silica fume replaces up to 25% cement, slag powder or fly ash replaces up to 30% cement. This investigation is expected to provide a practical method in the mix design and engineering application of economical and sustainable RPC.