Effect of axial compressive damage on gas permeability of ordinary and high-performance concrete

Gas permeability is commonly used to evaluate durability characteristics of concrete. However, these values are often achieved using never stressed or damaged specimens. The objective of this study is to examine experimentally the effect of axial compressive loading on the pemeability of three different types of concrete: ordinary concrete (OC), high-performance concrete (HPC), and high-performance steel fiber-reinforced concrete (HPFQ. Monotonic and cyclic loads are applied on 220 x 110-mm diameter specimens. Stress levels vary between 60% and 90% of the ultimate strength. At the end of the loading phase, a disc is extracted from the middle part of the cylinders and is dried in a ventilated oven, Four different gas permeability tests are conducted during the drying procedure. The results show that, for each drying stage, the gas permeability of the discs increases with the load-induced strain. A correlation is worked out between the increase in permeability and the applied-strain/yield-strain ratio. Finally, a relationship between mechanical damage indicators and the increase in permeability is also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.