Advanced sustainable concrete incorporating high-volume fly ash and porcelain aggregate reinforced with multiscale fibers: Systematic assessment

In recent years, civil engineering researchers have adopted an advanced approach by utilizing various waste materials in concrete alongside multiscale fibers, aiming to enhance both sustainability and their microstructural performance. This study explores the influence of multiscale fibers on concrete incorporating high-volume fly ash (FA) as a partial cement replacement and porcelain (PA) as fine aggregate. One objective was to experimentally and numerically determine the optimal proportions of FA (0–50 %) and PA (0–100 %) to achieve a characteristic compressive strength of 45 MPa. The following objective was conducted to assess the extent to which multiscale fibers, including 1 % steel fiber and 0.1 % graphene nanotubes, would enhance the optimized mixture's performance in compressive (CS), flexural (FS), direct tensile (TS), and impact resistance. The third objective was to examine microstructural characteristics using ICP-MS, XRD, and STA tests. Based on the results, even up to 50 % FA and 100 % PA, an acceptable compressive strength of 44.3 MPa was achieved at 28 days. Moreover, incorporating multiscale fibers further enhanced CS by 13.3 %, FS by 145.8 %, and TS by 44.4 %; meanwhile, energy absorption at the initial cracking stage significantly increased from 98.1 J to 5790.8 J. This remarkable enhancement was attributed to the bridging effect at the nano-, micro-, and macro-scales, as well as microstructure refinement activated by graphene and pozzolanic activity. Such an advanced sustainable concrete is suitable for applications that require a good tensile strength and impact resistance, such as rigid pavement.