Microstructure and properties of sustainable cement-based materials using combustion treated rice husk ash

Improving the performance of cement-based product using agricultural waste is one of the major challenges for developing sustainable construction materials, and rice husk ash from the recycling of rice husk, could be a great candidate to partially replace cement from this perspective. This study explored the hydration kinetics of cement-based materials (w/b ratio of 0.5) that incorporated with combustion treated rice husk ash (CRHA) through isothermal calorimeter test with the adoption of Krstulovic and Dabic model, while the mechanical and water absorption properties were also examined. Silica fume (SF) severed as SCM reference, and the dosage of the two additives ranged between 5% and 20% (by weight). The microstructure of the binary binding system was investigated with the aid of X-ray diffractometer (XRD), Thermogravimetry analysis/Differential thermogravimetry (TG/DTG), Mercury injection porosimeter (MIP) and Scanning Electron Microscopy (SEM). It was found that both CRHA and SF additions accelerated the hydration process, reflecting by the increased reaction rate constants (K-NG and K-I) correspondingly in nucleation and crystal growth process (NG) and in interaction at phase boundaries reaction process (I), while K-D in diffusion process (D) remained stable. The strength enhancement effect of blending CRHA started to show at early age of 3 d on mortars, and the compressive strength of CRHA blended mortars all exceeded that of SF blended mortars with the same replacement ratio at 28 d. Meanwhile, the permeability was declined for samples containing increased dosages of CRHA (15-20%). The superior properties from the addition of CRHA were mainly attributed to the significant consumption of Ca(OH)(2) and the pore structure refinement arised from CRHA. Furthermore, the connection between hydration heat release and water absorption at different temperatures was assessed to confirm the beneficial role of using increased dosages of CRHA in thermal cracking control. (C) 2021 Elsevier Ltd. All rights reserved.