This paper presents the results of an experimental investigation of pore structure development of expansive cement paste as a function of expansion strain and curing time. The expansion strain, bulk density, dynamic modulus, and evaporable water content of paste specimens were monitored periodically during and after termination of expansion and correlated with the pore size distribution data obtained by mercury intrusion porosimetry. It is shown that expansion results in the formation of large pores (and/or microcracks) in the paste. It appears that MIP has a limitation in that it cannot register the pores that form during the later stage of expansion. The mass of evaporable water appears to be a better way of characterizing changes in porosity during expansion, however, it does not reveal any information as to the pore size distribution
The effect of restraint by steel reinforcement on pore structure development of expansive cement paste was also studied. It was found that restraining expansive cement paste results in reduction of the size of large pores. However, even with a large degree of restraint, expansive cement paste is still more porous and contains larger pores than portland cement paste of the same age.