Effect of Pore-Size Distribution on Shrinkage of Concretes

The effects of pore structure of concrete made with slag-blended cement on shrinkage behavior of concrete when exposed to drying were presented in this paper. The investigated parameters were the length of curing (1-day and 7-day curing), slag and gypsum contents in mixtures. Pore structure analysis was studied by conducting mercury intrusion porosimetry and nitrogen gas adsorption technique tests. The results show that 65% slag concrete with 7-day curing exhibited the lowest shrinkage evolution compared to 0, 35, 50% slag mixes. This is attributed to the highest pore radius where meniscus forms when drying in these concretes. It was found that addition of gypsum in slag mixes tend to reduce the nanopores (within the range from 4 to 20 nm pore size) and decrease the proportion of mesopores. The higher proportion of mesopores and the lower value of meniscus pore radius could explain the increase in drying shrinkage of concrete made with 65% slag cement containing 0% added gypsum.