Porosity: Some characterization techniques

Abstract

In porous media, porosity performance is critical as it controls fluid flow. In civil construction, geology and others, the connectivity of the porous structure is directly related to this flow. The porosity of cementitious materials such as concrete, mortars and pastes have a complex internal structure of pores, being an easily defined parameter, but its quantification is not trivial. Thus, studying this complex porosity will be necessary to understand the total pore volume, size, and shape. Concepts such as tortuosity, percolation and connectivity influence mass transport in concrete and can influence mechanical properties such as strength, shrinkage and durability. Deterioration in reinforced concrete structures can be linked to attacks by sulfates, carbonation, chlorides that provide corrosion in the reinforcement. Because of this, a basic review is justified to better understand the porous structure of materials and thus adopt the technique that improves or facilitates decision-making where porosity exerts influence. Some techniques will be reviewed for their characterization, quantification, properties will be the focus of this work. The techniques to be reviewed for pore structure analysis will be: Nuclear Magnetic Resonance, Mercury Intrusion Porosimetry, X-ray computed microtomography. There are already studies interested in representing porous networks (voids and narrow openings) to later simulate the flow of fluids. Thus, currently, the digital reconstruction of porous materials is being used with free or commercial software. An explanation of this, given its importance, will be discussed shortly. Porous 2D imaging models compared to three-dimensional (3D) models are currently inefficient, but no less important. Three-dimensional models of porous networks better and more efficiently reproduce pore interconnectivity. Many mathematical modeling methods and numerical simulations to estimate the porosity of concretes, mortars and pastes are found in the literature and others are being developed. The reality is that porosity will always have a prominent role, importance and care that cannot be neglected due to its role in the transport of fluids in materials used in engineering.