Advances in engineering the microstructure of cementitious composites have led to the development of fiber reinforced Ultra High Performance Concretes (UHPC). The scope of this paper is twofold, ...first to characterize the nano-mechanical properties of the phases governing the UHPC microstructure by means of a novel statistical nanoindentation technique; then to upscale those nanoscale properties, by means of continuum micromechanics, to the macroscopic scale of engineering applications. In particular, a combined investigation of nanoindentation, scanning electron microscope (SEM) and X-ray Diffraction (XRD) indicates that the fiber-matrix transition zone is relatively defect free. On this basis, a four-level multiscale model with defect free interfaces allows to accurately determine the composite stiffness from the measured nano-mechanical properties. Besides evidencing the dominant role of high density calcium silicate hydrates and the stiffening effect of residual clinker, the suggested model may become a useful tool for further optimizing cement-based engineered composites.
The cost of producing concrete has increased, and its effects on the natural environment have become apparent. The ideal solution is to use agro-waste material instead of cement in concrete. Palm oil ...fuel ash (POFA) is a by-product of the burning of waste material at the palm oil power plant. Looking at the utilization of POFA in concrete research, there has been study conducted on the behaviour of properties of normal strength concrete containing POFA in terms of compressive strength performance. However, the performance of ultra-high strengthconcrete produced using POFA is still lack. This research aims to determine how well POFA works as a cement substitute in ultra-high-performance concrete (UHPC).It also to determine the mechanical properties of ultra-high-performance concrete (UHPC) withPOFA addition. In this study, the percentage of POFA used as a cement replacement was 5%, 10% and 15% by binder weight. The results were collected from slump test and compressive strength test. Tabulation and graph illustration were the methods used to present the data. The workability test conducted showed that with the increase of POFA addition to the UHPC, the workability of fresh concrete was reduced. Meanwhile, the compressive strength at 28 days, UHPC with 5% of POFA addition showed the maximum valueof compressive strength at 84.12 N/mm2.
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