关键词: 粉煤灰;改性;强度;自收缩

Abstract: The low grade fly ashes were modified through mixing with limestone.The microstructure, mineral phases and chemical compositions of the modified fly ashes were analyzed by using X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS).In addition,the effects of modified fly ashes on the strength and autogenous shrinkage of cement pastes were investigated,and the microstructure of cement pastes with the modified fly ashes were studied by the backscattered electron microscope(BSEM)and mercury intrusion porosimetry(MIP).The results show that β-C2S phase is formed on the surface of the modified fly ash particles, the hydration of β-C2S can generate C-S-H gels,the interface between cement matrix and fly ash particles improves,the porosity and the autogenous shrinkage of blended cement pastes decreases,and the strength of blended cement pastes improves.

Key words: fly ash;modification;strength;autogenous shrinkage