| Abstrakt: |
Abstract: To solve the problem of the reduction in strength due to the high-volume of fly ash (FA) in cement, this research investigates the influences of calcium carbonate nanoparticles (NCs) on the microstructure and strength of mortar containing 40% FA at the early and later ages. Two NCs (NC1 and NC2) were added at rates of 2% as a partial replacement for the binder, respectively. The characteristics of large capillary pores, the dense and porous areas, the constituent phase fractions, the hydration degree of the cement, the porosity, and the pore structure of mortar containing FA and NCs were analysed by backscattered electron imaging analysis (BSI). Mortar containing FA without NCs was used as a control mortar (PCFA). The results show that mortar containing 2% NCs exhibited about 13.6% and 6.7% higher compressive strengths than that of the PCFA at 3 and 180 days, respectively. Furthermore, the incorporation of the NCs decreases the porous hardened cement paste (HCP) areas, but increases the dense HCP. Besides, the results reveal that the hydration degree, the pore volume, and the larger capillary pores of the mortar containing the NCs is about 9.7%, 15.5%, and 30.5% lower than that of the PCFA at 3 days, respectively. The results of the BSI analysis also indicate that the NCs could reduce the porosity, the large capillary pores, and the porous HCP area of the mortar, creating a denser microstructure, resulting in a higher compressive strength in the later ages. |
