The objective of this study was to evaluate ultra high performance concrete (UHPC) as a precast product material containing portland type II cement, quartz powder, silica fume, silica sand, steel fiber, superplasticizer, water, and a specific amount of incinerator fly ash (IFA). The UHPC mixes containing different volumes of IFA were evaluated to find the optimum quality of precast production, while 2.5 % of steel fiber by volume was blended at every mix. The results indicate that the properties of UHPC exhibit high strength, ductility, and bonding stress. The compressive strength of UHPC decreases greatly as IFA for part replacement of cement or quartz powder increases. However, the flexural strength of UHPC decreases a little as IFA for part replacement of quartz powder increases. The results demonstrate that the UHPC products with 10 % or 15 % IFA were able to withstand a 98-kN proof load to the cover and frame without cracks or permanent deformation. It has to be noted that heavy metals that originated in the IFA are confined in the UHPC matrix and yield rather low leachability results.
Abstract-In this study, ultra high performance concrete (UHPC) was used to investigate the effect of UHPC and its precast product by the severe freeze-thaw testing. The UHPC to be used as a precast product material contains a large amount of cement and cementitious materials, a large amount of superplasticizer, and a very small amount of water. The UHPC mixes with eight different volumes of steel fibres were tested and evaluated to find the optimum quality of precast production. The results show that the mechanical properties of UHPC possess high strength, ductility, and bond stress. The results also indicate that most of UHPC specimens presented a steady decrease in compressive and flexural strength after freeze-thaw testing. The 2.5, 3.0 and 3.5% steel fibres by volume were chosen and used in UHPC precast products, after UHPC specimens were tested and finished on their performance evaluations. The results show that the loading capacity of UHPC precast products increased significantly after 600 free-thaw cycles. As a result of freeze-thaw resistance, the appropriate mixes of UHPC applied in the precast products have been obtained; it would provide a reference manufacturing for the UHPC products.Index Terms-UHPC, freeze-thaw, precast product, ultra high performance concrete.
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