Engineering properties of cement-based mortar with fly ash activated by sodium silicate

Abstract

This study focused on evaluating the enginnering properties of cement-based mortar with 20% ​​fly ash activated by sodium silicate (Na₂SiO₃) to improve the quality of construction mortar with fly ash used in construction works. The cement-based mortars were prepared with a water-to-binder ratio of 0.5 and a sand-to-binder ratio of 2.5. The Na₂SiO₃ contents were added to the mortars at 0, 2, and 4% by mass. After shaping and curing for 24±4 h in the molds, the mortar samples were demolded and cured in water before conducting the engineering properties tests. The engineering properties of the cement-based mortars investigated included flowability, flexural strength, compressive strength, and water absorption coefficient due to capillary action. The experimental results showed that the flowability of fresh mortars was in a range of 90 – 160 mm, the flexural strength and compressive strength at 28 d of mortar samples were in ranges of 5.5 – 12.2 MPa and 38.7 – 50.4 MPa, respectively, and water absorption coefficient due to capillary action at 28 d was in a range of 0.032 – 0.074 kg/m²·min^0.5. The addition of Na₂SiO₃ significantly affected the engineering properties of cement-based mortars containing 20% ​​fly ash. The relationships between the engineering properties of hardened mortars were also established. Consequently, among the three designed mortars, the cement-based mortar with 20% ​​fly ash activated by 2% Na₂SiO₃ as an optimal one had improved engineering properties.