Strengthening the Region of Intermediate Support of Continuous Reinforced High-Strength Concrete Slabs with New Cement

Concrete is being widely used as a construction material, hence it is necessary to improve its properties. These days supplementary cementecious materials are used for enhancement of concrete properties. Use of Nano materials is gaining importance due to its vital characteristics, these materials help in developing high performance concrete (Zhang Zenan, et al 2006).In this paper, the use of steel fibers instead of the reinforcement steel bars in the continuous nano-high strength concrete (NHSC) slab panel was experimentally investigated. Tests were carried out on three two-span slab panels under mid span point loads and simply supported at the panels end. The first slab was reinforced by steel bars to resist the negative moments near the internal supports while the other two slab panels were reinforced by steel fibers only of percentage of volume fraction (1 and 2.0) in this zone, without negative steel bars. 5% nano-SiO2 (NS) and 15% of silica fume (SF) contents were used. The load-deflection relationship for the tested slab spans is determined, the first crack load, failure load and deflections were recorded. Also a comparison between the results obtained from this study and that obtained from other study of two continuous slabs made of self compacted concrete (SCC) was made , one of these slabs was reinforced by steel bars near the interior supports and the other is reinforced by steel fibers of (1% and 2%) in this zone. Experimental results show that the ultimate load capacity are increased (15.4% - 32.9%) and the cracking loads are increased (40%-56%) for tested specimens strengthened with SFRC, in comparison with the reference specimens. The comparison between the NHSC slabs and corresponding SCC slabs shows a similar load-deflection curve but the ultimate strength capacity for the NHSC slabs with steel fiber gives ultimate strength larger than SCC  slabs with steel fibers, while the NHSC slabs reinforced by steel bars which show an important effect on the first cracking loading in comparison with SCC slabs. loading in comparison with CC slabs. Keywords: key words, Nano, negative moment, Self-Compacting Concret