Alexander Michel

Multi-Physics and Multi-Scale Deterioration Modelling of Reinforced Concrete

Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings represents one of the major challenges currently facing developed countries. While engineering tools and methods for structural modelling and design of new reinforced concrete infrastructure are mature, methods and tools for modelling decades-long deterioration and maintenance are much less developed. In this paper, a multi-physics and multi-scale modelling approach for structural deterioration of reinforced concrete components due to reinforcement corrosion is presented. The multi-disciplinary modelling approach includes physical, chemical, electrochemical, and fracture mechanical processes at the material and meso-scale, which are further coupled with mechanical deterioration processes at the structural scale.

Specimen or Core; In the Laboratory (Sides Available)

When also the sides, of a specimen or a core from a structure, are available during the moisture measurement procedure numerous techniques are applicable compared with when only the exposed surface is available.

Time Domain Reflectometry

Originally, the TDR measurement technique was developed to detect defects in telecommunication cables and electrical wires, Moffitt (1964). Within recent decades, TDR was also applied to determine and monitor volumetric moisture contents in particulate and porous media, in particular soil but lately also building materials such as building bricks, concrete, sandstone, etc., see e.g. Dobson et al. (1985), Topp et al. (1980), and Phillipson et al. (2008). TDR is in general based on the measurement of the propagation time of an electromagnetic signal along a wave guide also referred to as probe, usually there and back. In the low frequency range, i.e. <10 GHz, water possesses a considerably higher relative permittivity (e w ≈ 80) than mineral compounds (e s ≈ 4) or air (e a ≈ 1). From the measurement of the propagation time of an electromagnetic signal along a wave-guide, the mean relative permittivity, which is among others moisture dependent, of the investigated dielectric material is derived from the reflection picture. Subsequently, the volumetric water content can be determined directly from the mean relative permittivity applying suitable material functions, which relate mean relative permittivity and volumetric moisture content.

Multi-physical and multi-scale deterioration modelling of re-inforced concrete: modelling corrosion-induced concrete damage

In this paper, corrosion-induced damage is investigated by means of numerical simulations utilizing a coupled lattice and finite element method (FEM) modelling approach. While the reinforcement and corrosion product domain are discretized by the FEM, a lattice approach is used for the discretization of the concrete domain. To model the expansive nature of solid corrosion products, a thermal analogy is used. The modelling approach further accounts for the penetration of solid corrosion products into the available pore space of the surrounding cementitious materials and non-uniform distribution of corrosion products along the circumference of the reinforcement. Finally, results of numerical simulations in terms of corrosion-induced deformations and cracking are compared to experimental data obtained by digital image correlation and published in the literature.