Preliminary Study on the Durability Properties of High-Volume Fly Ash Mortar Composites

摘要

The use of fly ash, a common industrial byproduct waste, is gaining popularity, especially in developing countries, in addressing environmental concerns surrounding the construction industry, such as reducing waste and CO_2 emissions. However, the full potential of fly ash usage is yet to be exploited. The physical, mechanical, and durability properties of fly ash in concrete are well documented; in contrast, its durability properties in mortar require further investigations. The present study investigated the durability properties of high-volume fly ash (HVFA) mortar composites. Specifically, varying proportions of sand were replaced with cement and fly ash to examine the effects on the durability properties of the resulting mortar composites by studying the porosity, weight loss upon sodium sulfate attack, and ultrasonic pulse velocity (UPV). Specimens with a diameter of 50 mm and height of 100 mm were examined. The results showed that UPV_(mOrtar )> UPV_(pastes). Increasing the amount of cement led to a decrease in weight loss for the 50-, 150-, and 250-mm slumps. The maximum weight loss (15 %) was recorded for the HVFA mortar composites comprising 80 % sand. Furthermore, all prepared samples displayed adequate resistance to sulfate (weight loss was below 16 %). Based on the dry unit weight values, all the final products, aside from that comprising 20 wt. % fly ash and 80 wt. % cement, can be considered as a lightweight material, at ～12.58 kN/m~3, and can satisfactorily be used in the manufacture of lightweight aggregates and semi-isolating materials.