Mechanical and micro properties of concrete slurry waste geopolymer under various curing conditions
Juncai Wang, Jiarui Liu, Z.H. Ren, Tianyu Sun, Jeung‐Hwan Doh
Abstract
Amid accelerating urbanization, the extensive use of concrete poses significant environmental challenges, particularly from the generation of concrete slurry waste (CSW). The high alkalinity and substantial volumes of CSW escalate recycling costs. Existing strategies, focused on reusing CSW into concrete production, fall short of addressing environmental pollution fundamentally. Geopolymer, now viewed as a sustainable alternative to ordinary Portland cement, has validated fly ash (FA) as an effective aluminosilicate precursor (AP). Herein, this study introduces a novel methodology to incorporate CSW into FA-based geopolymer. The impacts of CSW replacement ratio, alkali concentration, and curing conditions on the mechanical properties of geopolymer are examined. It has been preliminarily observed that elevated curing poses a positive impact on the strength of CSW-FA geopolymer whilst the CSW addition poses a negative one. Notably, under elevated curing, geopolymer with a 25% CSW replacement ratio consistently maintains a strength activity index above 80%. Further, the crystalline & amorphous phase and elemental concentration under various CSW replacement ratios and curing conditions were characterized. Tests indicate that Calcite is a significant reaction product from the addition of CSW, whilst elevated curing can facilitate the formation of Albite and Anorthite but inhibits the generation of Larnite and Bavenite. Furthermore, this study innovatively explores the correlation between the elemental molar ratios in bulk and crystalline composition with the strength of the resultant CSW-FA geopolymer. The Na/Ca molar ratio in the crystalline composition exhibits a strong and positive correlation.