Experimental investigation on workability and mechanical properties of carbon fiber reinforced high-strength concrete (HSC) containing waste bakelite aggregate (WBA)

Abstract

High-strength concrete (HSC) is a type of concrete that is, due to its improved mechanical and durability properties, most often used in the construction of high-demand structures such as bridges, structural elements in aggressive environments, skyscrapers, and large-span constructions. In order to obtain high-strength concrete, a larger amount of cement is required, which can lead to questionable ecological acceptability of this material. To reduce the ecological footprint of this material, supplementary cementitious materials such as silica fume or metakaolin are often used. By reducing the porosity and increasing the density of the concrete mixture, fine particles of supplementary cementitious materials have a positive effect on the mechanical and durability properties of high-strength concrete. Along with cement and supplementary cementitious materials, another important component of high-strength concrete is aggregate, which is in most cases a fine aggregate. In this research, the natural fine aggregate was partially replaced with bakelite plastic waste, and the influence of this replacement on the fresh and hardened properties of high-strength concrete was presented. Seven mixtures were designed, a reference mixture and six other mixtures in which supplementary cementitious materials, waste bakelite aggregate, and carbon fibers were combined to produce environmentally friendly high-strength concrete. 5 % of the cement mass was replaced with silica fume or metakaolin, 10 % volume of natural fine aggregate was replaced with waste bakelite aggregate (WBA) and carbon fibers were added in the amount of 0.5 % of the cement mass. In a fresh state, the workability of HSC is determined by using a flow table. To determine the influence of waste bakelite aggregate on mechanical properties, flexural and compressive strength tests were carried out on 7- and 28-day-old samples. The test results indicate that the combined effect of waste bakelite aggregate, supplementary cementitious materials, and carbon fibers can be a promising solution not only to improve high-strength concrete mechanical properties but to potentially save millions of tons of natural fine aggregate and preserve natural resources and the environment.