Effective Microorganisms and Glass Nanopowders from Waste Bottle Inclusion on Early Strength and Microstructure Properties of High-Volume Fly-Ash-Based Concrete

In concrete production, the use of high-volume fly ash (FA) as the cement substitute became interesting to achieve more sustainable and eco-friendly construction materials. However, concrete produced using high volumes of FA as cement substitute suffers from various limitations such as low strength at early ages. Considering the engineering solutions and economy of FA-included concrete, it has become vital to address such issues. In this perception, some concrete mixes were designed using more abundant and low-cost local waste materials such as waste glass bottle nanopowders (WGBNPs) and effective microorganisms (EMs) to determine the feasibility of compensating for the strength loss at early ages due to FA inclusion. The proposed mixes contained 10% of EMs as water replacement, 50% of FA, and various percentages of WGBNPs as cement replacement. The effects of EMs and WGBNPs inclusion on the early strength and microstructure properties of the produced FA-based concrete mixes were determined. The results show that the strength indexes of the concrete at all test ages were improved due to WGBNP and EM incorporation. At almost all curing ages, the mechanical performance of the concrete made with 10% EMs and 4% WGBNPs was comparable to that of normal concrete (control mix), wherein the mix containing 6% WGBNPs outperformed the control mix. The microstructure analysis of the studied mixes revealed an increase in the hydration products, structural compactness, and homogeneity due to the synergy of WGBNPs and EMs, especially the specimen made using 10% EMs and 6% WGBNPs. It is established that the proper utilization of EMs and WGBNPs in FA-based concrete can be beneficial for waste recycling and landfill problems, thus lowering environment pollution.