Pore Structure Changes in Hardened Cement Paste Exposed to Elevated Temperature

Abstract

Hardened cement-based materials exposed to the high temperatures of a fire are known to experience change in the pore structure as well as microstructural changes that affect their mechanical properties and tend to reduce their durability.In this experimental investigation, hardened Portland cement pastes were exposed to elevated temperatures of 200, 400, 600, 800, and 1000°C for 60 minutes, and the resulting damage was studied by thermogravimetry (TG), mercury intrusion porosimetry (MIP) and density measurements.These results revealed that the residual compressive strength is increased at temperatures greater than 400°C due to a small pore size of 3 nm and/or rehydration of the dehydrated cement paste.However, a loss of the residual strength occurs at temperatures exceeding 500 and 600°C.This can be attributed to the decomposition of hydrates such as portlandite and to an increase in the total porosity.