Physico-durability aspects of partial substitution via pelletized fly ash lightweight nano-silica concrete

Abstract

This study's main goal is to examine the durability and shrinkage properties of high-performance lightweight concrete (HPLC) which uses lightweight synthetic fly ash instead of some natural coarse aggregate. By combining 90% fly ash and 10% Portland cement by weight in a tilted rotating pan at room temperature and curing the aggregate for 28 days, the synthetic aggregate was created using the cold bonded pelletization procedure. Then, ten combination samples were made using HPLCs by substituting natural coarse aggregate for fly ash aggregate at percentages of 0, 10, 20, 30, and 40% of the aggregate's total volume with a water binder (w/b) ratio of 0.35 both with and without the addition of nano-SiO2 (nS). Durability characteristics, rapid chloride penetration and water permeability, were tested for 28 and 90 days, while drying shrinkage and weight loss were examined for 61 days. Results demonstrated a lower performance with control mix in terms of durability and shrinkage characteristics with increasing the coarse aggregate replacement (%) of lightweight aggregate (LWA). Additionally, nS improved the transport qualities by reducing the porosity traits and detrimental effects of synthetic LWAs. On the other hand, nS particle-related permeability decreases up to 23.34% due to a larger surface area and smaller particle size that made a permeability channel more meandering or partially closed. HPLCs mixes greatly reduce the overall shrinkage strain when adding 3% nS to HPLC specimens by 11.73% over 61 days. The statistical models that were derived indicated that the independent variables have a statistically significant impact.