The effect of compressive loading on the residual gas permeability of concrete (original) (raw)

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

Cement and Concrete Research, 2001

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 permeability of three different types of concrete: ordinary concrete (OC), high-performance concrete (HPC), and high-performance steel fiber-reinforced concrete (HPFC). Monotonic and cyclic loads are applied on 220 Â 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. D

Effect of confining pressure on gaseous transport properties of concrete

The effect of confining pressure on the transport properties of cementitious materials has received little attention. This paper presents an investigation of the influence of confining pressure on the oxygen diffusivity and permeability of concrete samples dried in different ways to induce microcracking prior to transport testing. Transport properties of each sample were measured at several confining stresses up to 1.9MPa, and results were normalized and compared. The characteristics of the microcracks were quantified using fluorescence microscopy and image analysis. The results show that gaseous transport properties of microcracked specimens decreased significantly when the confining pressure was increased. The effect was more significant for permeability than for diffusivity, and for specimens with larger crack widths. The results suggest that closure of microcracks occurs when specimens are confined at relatively low stresses and that this influences transport properties. The confining pressure used in transport testing is an important parameter that could influence results and should be taken into consideration when interpreting results. The wider implications of these results are also discussed.

Gas and water permeability of concrete

Geological Society, London, Special Publications, 2014

Concrete is used as a barrier on surface or near-surface facilities for the final disposal of low- and intermediate-level radioactive waste, where gas can be generated and affect the hydraulic properties and the processes taking place in concrete. In this framework, gas-transport properties of concrete samples were investigated using two different laboratory test set-ups: a non-steady-state equipment working under low injection pressures; and a newly fine-tuned steady-state set-up working under different pressures.Permeability decreased with water content increase but was also greatly affected by the hydraulic history of concrete (i.e. if it had been previously dried or wetted). The intrinsic permeability determined with gas flow was about two orders of magnitude higher than that determined with liquid water (10−16 v. 10−18 m2), probably due to the chemical reactions taking place during saturation (carbonation). The relative gas permeability of concrete increased sharply for water d...