Numerical simulation of cementitious materials degradation under external sulfate attack

Abstract

a b s t r a c tA numerical methodology is proposed in this paper to simulate the degradation of cementitious materials under external sulfate attack. The methodology includes diffusion of ions in and out of the structure, chemical reactions which lead to dissolution and precipitation of solids, and mechanical damage accumulation using a continuum damage mechanics approach. Diffusion of ions is assumed to occur under a concentration gradient as well as under a chemical activity gradient. Chemical reactions are assumed to occur under a local equilibrium condition which is considered to be valid for diffusion controlled reaction mechanisms. A macro-scale representation of mechanical damage is used in this model which reflects the cracking state of the structure. The mechanical and diffusion properties are modified at each time step based on the accumulated damage. The model is calibrated and validated using experimental results obtained from the literature. The usefulness of the model in evaluating the mineralogical evolution and mechanical deterioration of the structure is demonstrated.

Development and Verification of an Integrated Physicochemical and Geochemical Modelling Framework for Performance Assessment of Cement-Based Materials

“…Overall, the proposed model reproduces the experimental results despite some discrepancies. The important features such as dissolution of portlandite, monosulphate and C-S-H, and formation of ettringite and gypsum associated with the ingress of sulphate are consistent with other data reported in the literature (Lothenbach et al 2010b;Samson and Marchand 2007;Sarkar et al 2010). Thus, cementitious materials under sulphate attack can reasonably be simulated using the model developed in this study.…”

Alternative methodology to consider damage and expansions in external sulfate attack modeling

“…Traditionally, the increase in diffusivity due to cracking was related to a damage parameter (w) defined by an isotropic damage model based on continuum damage mechanics [3,11,15]. In this work, a more direct and intuitive approach is presented, based on the idea that the loss of concrete strength is directly related to the cracking state of concrete, and hence, to the increase in diffusivity.…”

“…In the first of them, expansion are a result of the additional volume generated by ettringite formation (e.g. [3,11,17,26]). In the second of them, expansions are caused by the crystallization pressure exerted on the pore walls due to the formation of ettringite from supersaturated solution within small pores (e.g.…”

“…Most of the models referred above [3,4,11] obtain the expansions using a simplified expression described by Tixier & Mobasher [11]. In this expression, the pores capacity to accommodate ettringite is represented by a single buffer coefficient ( ).…”

Demonstration of Leachxs/Orchestra Capabilities by Simulating Constituent Release From a Cementitious Waste Form in a Reinforced Concrete Vault

“…Modeling sulfate attack and cracking due to ettringite formation. A detailed example for this case is provided in a separate article by the authors (Sarkar et al 2010). …”