Shrinkage of hardened cement paste at temperatures up to 670 degrees C (1238 degrees F)

The shrinkage behavior of sealed specimens of portland cement paste of 0.3 w/c ratio was examined at < or = 670 degrees C. Increase in shrinkage was virtually monotonic with max exposure temp. until a certain temp. was reached, at which point the increasing trend was reversed. The amount of shrinkage experienced and the temp. at which reversal occurred decreased with decreasing w/c ratio. Pastes with a low w/c ratio contained more unhydrated cement grains of larger size. Shrinkage phase was modeled mathematically using a combined logarthmic and exponential expression.