Correlating damage and cracking with air (gas) permeability in concrete using the Brazilian tension test

Abstract

• Using acoustic emission and digital image correlation in the indirect Brazilian tension test, damage and cracking can be correlated to gas permeability in concrete. • A microcrack size of 40 µm can distinguish between pre-cracking and post-peak behavior of concrete. • Gas permeability of concrete increases to almost half an order of magnitude in the pre-peak region. • Gas permeability of concrete increases to about six orders of magnitude during the progression of cracking in the post-peak region. This article investigates the relationship between stress, damage, crack propagation, and air (gas) permeability evolution in concrete using the Brazilian tension test. This investigation is important for situations where hazardous gases are in contact with concrete as it quantifies the effect that damage of concrete has on gas permeability. Cylindrical concrete disc specimen of diameter 101.6 mm and thickness 50.8 mm were used for this study. Acoustic emission sensors are used to observe damage occurrence and propagation in the concrete, while a digital image correlation set-up is used to precisely measure the crack opening displacement. A vacuum flow system is attached to the rear side of the concrete under loading to measure apparent air permeability through the concrete specimen before and after cracking. The collected data is synchronized and analyzed to correlate damage and crack propagation and air permeability evolution in concrete under tension stresses. It was found that the air (gas) permeability increased by over six orders of magnitude as the concrete cracking occurs and changes in air (gas) permeability directly correlate with changes in concrete damage and fracture.