Microstructure, XRD, and strength performance of ultra-high-performance lightweight concrete containing artificial lightweight fine aggregate and silica fume

Ultra-high-performance lightweight concrete (UHPLC), a sustainable and environmentally friendly concrete crafted with artificial lightweight aggregates to preserve non-renewable natural resources like river sand, has garnered significant attention due to its exceptional mechanical properties. This study explores the use of artificial lightweight fine aggregate (ALWFA) as a substitute for fine aggregate in UHPLC production, investigating both fresh properties and mechanical performance. Microstructure analysis, utilizing SEM, and crystalline phase evaluation, employing XRD, were also conducted. The study results indicated that due to the irregular shape of ALWA particles with sharp edges, increasing the content of ALWFA led to a reduction in the flowability of UHPLC. Additionally, it was found that increasing the amount of ALWFA as a replacement for fine aggregate negatively affected both the compressive and tensile strength of UHPLC. This reduction in strength can be attributed to the higher porosity and lower intrinsic strength of ALWFA particles, as well as the weaker cohesion between ALWFA particles and the matrix. SEM analysis revealed that elevating the ALWFA content as a replacement for fine aggregate resulted in an increase in both the number and dimensions of voids, which is responsible for the weaker performance of ALWFA concrete. Finally, XRD analysis showed no significant alteration in the crystalline phases as the ALWFA content increased.