الفهرس 
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Abstract
ABSTRACT
The purpose of this study is evaluating the single and combined effect of marble dust (MD), granite dust (GD) and nano alumina (NA) on the performance of Portland cement concrete (PCC). Portland cement was individually replaced by different percentages (2, 4, 6, 8 and 10 wt%) in case of MD and GD. In addition, NA was used as addition by different percentages (0.25, 0.5, 0.75, 1.0 and 1.25 wt%) in the mixture individually. The optimal outcome percentages for MD, GD and NA were used to design two concrete mixtures with combined MD6%+NA1% and GD6%+NA1%. The physical properties (consistency, setting times and slump), the mechanical properties (compressive, splitting tensile and flexural strengths) and microstructure analysis (X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray (EDX)) were carried on the single and combined mixtures in addition to control mix. The results showed the water of consistency increased, whereas the initial and final setting times were shortened with the increase the content of GD and NA, while there is no obvious difference in case of MD content, compared to control mix. NA highly reduced the workability due to the high surface area. Also, GD reduced the workability of fresh concrete mixes, while MD reduced the workability slightly. For hardened concrete, there was an improvement in strengths at all curing ages of concrete with individual MD and GD content up to 6%, followed by a decrease in strengths when the content reached 10% of cement replacement compared to control sample. Concrete mixtures with addition of NA showed significant improvement in strengths at all percentages of addition until reached the maximum increase in strength at 1% then slightly decreased. Concrete with combined MD6%+NA1% and GD6%+NA1% show significantly improved mechanical properties and compact microstructure enriched with C-S-H in comparison to concrete samples using MD6%, GD6% and NA1% separately.