Effect Of Cooling Regimes And Polymer Impregnation On Permeability Of Concrete After Exposure To Elevated Temperature

In this thesis, an experiment was conducted to study the effect of cooling regime and polymer impregnation on the permeability of concrete exposed to high temperature. Concretes at water-to-binder ratios (W/B) of 0.26 and 0.60 incorporating polypropylene fiber (PP-fiber) or hybrid fibers (i.e. steel fiber and PP-fiber) were prepared. Internal and near-surface permeability of the concrete after exposure to two cooling regimes (i.e. natural cooling, quenching in water; target temperature: 200℃, 400℃, 600℃.) was investigated. Based on these experimental results above, further experiments were conducted to determine the effects of polymer impregnation on near-surface permeability, compressive strength and tensile splitting strength of concrete after exposure to high temperature, and compared with those of concretes before and after elevated temperature.The experimental results demonstrated that the cooling regime significantly affected the permeability of concrete after heat treatment. For the same peak temperature, the permeability of concrete quenched in water was higher than concrete subjected to natural cooling as quenching in water increased the amount of internal defects.Concrete incorporating low dosage of PP-fiber (Vf<0.1%) appears to have reduced internal permeability compared to plain concrete. But it appears to have increased near-surface permeability because the effect of thermal stress is more pronounced. As for hybrid fibers, regardless of cooling regime, near-surface and internal permeability were both lower than that of plain concrete, suggesting that hybrid fibers can reduce the effect of thermal stress on concrete permeability.After cooling, the near-surface permeability was higher than the internal permeability, and the degree of permeability increment was lager when the concrete was quenched in water than that cooled naturally.Polymer impregnation can efficiently improve permeability and residual mechanical properties of concrete exposed to high temperature. After exposure to high temperature, the permeability of concrete increases significantly. Near-surface permeability of concrete after exposure to elevated temperatures and polymer impregnation could recover to the original value of concrete before thermal exposure. Mechanical properties of concrete at a high W/B ratio exposed to elevated temperature and polymer impregnation recover better than those at a low W/B ratio.