Laboratory evaluation of self-compacting fiber-reinforced concrete modified with hybrid of nanomaterials

The idea of using nanomaterials to improve the bonding of fiber and cementitious matrix is a strategy involving simultaneous and effective use of fibers to enhance concrete mechanical properties on the one hand and decreasing concrete permeability by improving microstructure density on the other hand. Successful application of this idea in self-compacting concrete is an efficient solution for successful use of this product in production of unreinforced prefabricated elements. In this research, optimization of mixing plan of fiber concrete including optimal fiber contents, the largest nominal size of aggregate and optimal fiber size was investigated to achieve the best performance. In the first step, laboratory program including self-compacting fresh concrete tests, compressive strength, tensile strength, flexural strength, modulus of elasticity, as well as initial and final water absorption was administered and in the second step, the effect of aluminum oxide nanoparticles and silicon oxide on basalt fiber concrete designs was investigated. Results obtained from flexural strength test showed that, addition of 2 and 3% of nano-silica resulted in an increase in the concrete yield by 21 and 27% compared to non-nanomaterial fiber concrete. Similarly, the use of 2 and 3% of nano-alumina led to increased flexural strength by 10 and 15%. This improvement in the performance of nanoparticles increased the bonding between fiber and cementitious matrix in other mechanical property tests such as tensile splitting strength and modulus of elasticity. Results showed that addition of basalt fibers causes a decrease in the flowability indicators of self-compacting concrete, but it has no significant effect on compressive strength index. Additionally, application of 3% nano-silica and 3% nano-alumina in separate designs resulted in a 19 and 15% decrease in the initial water absorption of concrete, respectively, indicating improved macro, and micrometer densities of fiber concrete. (C) 2019 Elsevier Ltd. All rights reserved.