Various gas transport properties in concrete considering transporting mechanisms and testing methods-A review

Abstract

Atmospheric environment vitally affects concrete durability. In concrete durability design, gas transport property has been recently observed extensive employment. During the gas transport process, non-negligible collision between gas molecules and pore walls occurs, which is more complex when compared to the transports of liquid–water and chloride in concrete. Besides, phase-change and/or chemical reactions can occur along with several gas types of transport, e.g., water–vapor (H2O(g), liquid–gas phase transition), and carbon dioxide (CO2, carbonization reaction). As such, in this work, various gas types of transport covering inert gas (i.e., Nitrogen, N2), phase-change gas (i.e., H2O(g)) and reactant gas (i.e., CO2) in concrete are reviewed, and their mechanisms and testing methods are also severally summarized for analyzing their transport properties. The analysis reveals that these three categories of gas transports can be executed by the concentration or pressure difference and their corresponding testing methods are also different as well as their correlations. Furthermore, various factors affecting inert-gas permeability have been also summarized in detail, mainly containing pore structure, saturation degree, osmotic-medium, environmental temperature, and loading. The main challenge currently of gas transport investigation is that the relationship between various gas transport properties should be investigated in-depth as well as their relations to the other osmotic mediums and engineering for concrete structure design. This review intends to make a fine addition to the traditional evaluation of concrete design from the perspective of gas transport thus improving gas transport in the application of engineering.