Impact of reinforcement-concrete interfaces and cracking on gas transfer in concrete

Abstract

The durability of reinforced concrete structures is largely impacted by their transfer properties, which can be evaluated through, for example, permeability measurement. Usually, concrete permeability is studied on plain specimens and the effect of the presence of steel bars on permeability in reinforced concrete has been little studied in the literature. The steel-concrete interface presents a larger porosity than plain concrete, which can be the cause of preferential percolation paths for fluids. Such percolation paths could create a lower resistance to fluid transfer and modify transfer kinetics. For reinforced and prestressed structures with large reinforcement contents, such as found in nuclear power plants, the impact of the reinforcement on gas transfer should be identified to obtain a better assessment of the flow within the structure. The aim of this experimental study is to characterize the effect of the presence of reinforcement on such flows by measuring leakage rates, permeability, and time to reach the steady state. Measurements were performed with a Cembureau constant head permeameter on cylindrical concrete specimens with or without steel bars. Since gas transfer into concrete depends on the rate of saturation of the material, the specimens were tested at different degrees of saturation: 0%, 6%, 30%, 60%, 80%, 90% and 100%. The analysis quantifies the impact of the defects created by the steel bar for each state. The results show that material composed of concrete and reinforcement can be divided into two distinct permeability zones: the plain concrete and the steel-concrete interface with or without cracking.These two zones can be associated in series and/or in parallel according to the configuration. The consequences on permeability measurement in reinforced structures are discussed.

Effect of cementitious capillary crystalline waterproofing coating on the gas permeability of mortar

“…Permeability is defined as the ability of a material to allow fluids to pass through it, and this property governs the flow rate of a fluid through a porous medium . The gas permeability test was performed through the improved CEMBUREAU device.…”

New approach for the measurement of gas permeability and porosity accessible to gas in vacuum and under pressure

“…To compare the permeability obtained in vacuum and under pressure, tests were performed on two ordinary concretes [9], [19]. Their common characteristics are: the same cement CEM I 52.5 NCE CP2 NF: 320 kg/m 3 and the ratio Gravel / Sand is equal to 0.83.…”

“…It was important to test the measurements and the analysis on samples with significant defects. Specific reinforced samples with embedded steel bars were used to obtain samples with preferential percolation paths as explained in [9], [19]. Such percolation paths have large impact on the apparent permeability of the sample and perhaps on their porosity.…”

Modelling on crack propagation behaviours at concrete matrix‐aggregate interface

“…The interfacial problems in concrete materials have been studied in previous literature . Although analytical approach of modelling crack in concrete can provide accurate solution in engineering practice, they are still limited to certain special cases such as restricted boundary conditions.…”

“…The interfacial problems in concrete materials have been studied in previous literature. [8][9][10] Although analytical approach of modelling crack in concrete can provide accurate solution in engineering practice, they are still limited to certain special cases such as restricted boundary conditions. For example, a combined analytical and experimental study using a single leg-bending specimen under four-point bend loading performed to characterize mixed mode fracture of glass fiber reinforced polymer (GFRP) concrete-bonded interface.…”