Laboratory Investigation of Ultra-High-Performance Fiber-Reinforced Concrete Modified with Nanomaterials

High-performance concrete with fibers and nanomaterials possesses mechanical properties that are significantly different from normal-strength concrete materials. This article presents the laboratory investigation carried out to study the behavior of ultra-high-performance fiber-reinforced concrete modified with nanomaterials. The aim of this study was to use an optimum composite of nanoalumina, nanolime, nanosilica, and polypropylene fibers to improve the mechanical properties of the concrete. The results of compression and flexure tests showed that the addition of nanolime, nanosilica, and nanoalumina with the optimum mixing ratio could be a good alternative to increasing the amount of cement to increase the compressive strength of the concrete. Adding an extra amount of nanolime in compressive strength should be done cautiously, but the effect of nanosilica is far less sensitive. The results showed that using 30-kg/m(3) nanosilica, 5-kg/m(3) nanolime, and 0.75-kg/m(3) fiber produced the best result. In the test of concrete durability in acidic and noncorrosive environments, these amounts showed higher acid resistance. Increasing the amount of nanolime and nanosilica alone increases the flexural strength, while increasing the amount of nanomaterials or fiber will reduce it. The effect of increasing the amount of cement on the increase in flexural strength is much less than increasing the amount of nanomaterials. Also, the relationship between flexural strength and compressive strength was estimated for laboratory tests in fiber-reinforced concrete modified with nanomaterials compared with conventional ones. This study has shown that the American Concrete Institute experimental relationship between compressive strength and flexural strength is not consistent with this type of ultra-high-performance concrete.