Expansive hydration products of circulating fluidized bed combustion (CFBC) ash with different finesses are investigated in this paper. The results show that expansion occurred in hardened paste of CFBC ashes is mainly due to formation of dihydrate gypsum and ettringite. Besides, the free lime does indirectly cause expansion due to its effects on crystallization of ettringite. It also has been observed that linear free expansion rate of paste with ground CFBC ash is higher than that of paste using original ash at 1 day of hydration, but lower than paste with original ash 3 days and longer period of hydration later.

This paper studies the effects of high-volume composite mineral admixture made of limestone powder and low-quality fly ash on the properties of concrete,and studies the form of attack of cement-based material made of limestone powder at low water-binder ratio under low-temperature sulfate environment.Through experiments, this paper makes clear the workability of fresh concrete and analyzes the law of strength development of concrete. The experimental results indicate that the concrete with high-volume limestone powder as composite mineral admixture has good fresh properties; due to low water consumption per unit volume, medium-and-high-strength concrete can be prepared. As new type concrete mineral admixture, the composite mineral admixture made of limestone powder and low-quality fly ash will play an active role in the sustainable development of concrete industry. After the specimen with the water-binder ratio of less than 0.4 and the limestone powder volume of greater than 20% is soaked in 10% magnesium sulfate solution at low temperature at the age of 200d, gypsum attack-led destruction is caused to the concrete test cube, without thaumasite sulfate attack.