Effect of fly ash on the pore structure of cement paste under a curing period of 3Â years

The service life and durability of concrete structures strongly depend on the transport properties of the concrete. These transport properties are highly related to their microstructure, especially the pore structure of the hydrated cement paste. In this paper the microstructure development of cement paste and cement paste blended with fly ash is investigated, from solid phase to pore phase, at a long-term curing period up to 3 years. The solid phases are observed by environmental scanning electron microscope. The pore structure of blended cement paste is determined by mercury intrusion porosimetry. The results indicate that the addition of fly ash increases the total porosity of cement paste, not only at early ages, even at curing age of 3 years. The voids in hollow fly ash particles act as ink-bottle pores with progress of the pozzolanic reaction of fly ash, resulting in the increase of the total porosity of blended cement paste.