Influence of Nano Silica on the compressive strength and flexural behaviour of Bridge rubberised concrete

Based on the need of light weight concrete used in the bridge construction to reduce loadings on foundation and in the same time maintain enough strength to resist the stresses developed from the structure. Incorporation of recycled rubber from scrap tires in concrete as a partial replacement of course aggregate in production of new type of recycled aggregate lightweight concrete has provided many beneficial effects to both concrete and environments. Many properties of tire rubber concrete are improved compared with normal concrete. However, disadvantage such as reduction in rubber concrete strengths have limited the application of rubber concrete drastically. Therefore, this study presents a new method on producing rubber concrete with comparable compressive strength to Normal concrete strength (without rubber aggregate) by adding Nano silica as a partial replacement of binder (cement). The experimental program includes Four mixes, with one ratio of rubber (10 %,) as a partial replacement of course aggregate by weigh and, one of them is the reference rubberized concrete mix (without NS) and the other three is with three different ratios of Nano silica (0.5%, 1% and 1.5%) from the weight of cement. The experimental program also includes 36 samples were prepared and tested as 6 cubes for compression strength test, three of them in age of 7 days and the other three in age 28 days, and 3 prisms for flexural strength test. The data that obtained from the experimental program indicates that the compression and flexural strength properties of the rubber concrete increases nonlinearly with the increase of Nano silica ratio. The comparison between reference rubber concrete samples (without Nano silica) and other rubber concrete samples (with Nano silica), showed that the compression strength of rubber concrete in age of 7 days increases about (15%, 28% and 43%) for Nano silica (NS) ratio of (0.5%, 1% and 1.5%) respectively The increase in flexural strength was less but still obvious which is about(9%, 15% and 26%) for Nano silica (NS) ratio of (0.5%, 1% and 1.5%) respectively as well. The ultimate strength results of rubberized concrete with NS that obtained from the experimental work was with highest ratio of NS 1.5%.