Numerical analysis and computing of free boundary problems for concrete carbonation chemical corrosion

[EN] This paper deals with the construction, analysis and computation of a numerical method to solve a moving boundary coupled nonlinear system of parabolic reaction-diffusion equations, arising in concrete carbonation problems. By means of a front-fixing transformation, the domain of the problem becomes fixed, and the position of the moving carbonation front has to be determined together with the mass concentrations of the involved chemical species. Qualitative properties like positivity and stability of the numerical solution are established. Spatial monotone behaviour of the solution is also proved. Numerical examples illustrate these results.This work has been partially supported by the Ministerio de Economia y Competitividad Spanish grant 2017-89664-P.Piqueras-García, MÁ.; Company Rossi, R.; Jódar Sánchez, LA. (2018). Numerical analysis and computing of free boundary problems for concrete carbonation chemical corrosion. Journal of Computational and Applied Mathematics. 336:297-316. https://doi.org/10.1016/j.cam.2017.12.036S29731633

Multiscale carbonation reactions: Status of things and two modeling exercises related to cultural heritage

Having in mind as target audience beginner researchers working in the field of cultural heritage, we present succinctly the concept of two-scale modeling of reaction-diffusion problems as it fits to scenarios where the action of the carbonation reaction is relevant. We briefly review well-known contributions concerning multiscale concrete carbonation processes, and finally, we point out two related multiscale modeling exercises. The scope of these notes is twofold: Promoting the language of multiscale modeling, we invite the applied mathematician to pick some of the target problems from the context of cultural heritage. On the other hand, we invite the experimentalist to talk to the applied mathematician whenever the laboratory experiments are unable to answer questions for instance about the long time behavior of materials exposed to the ingress of various chemical species, humidity, and/or temperature (as it is the case of historical monuments and buildings in urban areas) because modeling and simulation approaches might provide at least provisory hints on what could happen further once measurements stop, or when the situation of interest takes place actually outside the laboratory.Comment: 12 pages, 1 figur

Data-driven method for enhanced corrosion assessment of reinforced concrete structures

Corrosion is a major problem affecting the durability of reinforced concrete structures. Corrosion related maintenance and repair of reinforced concrete structures cost multibillion USD per annum globally. It is often triggered by the ingression of carbon dioxide and/or chloride into the pores of concrete. Estimation of these corrosion causing factors using the conventional models results in suboptimal assessment since they are incapable of capturing the complex interaction of parameters. Hygrothermal interaction also plays a role in aggravating the corrosion of reinforcement bar and this is usually counteracted by applying surface protection systems. These systems have different degree of protection and they may even cause deterioration to the structure unintentionally. The overall objective of this dissertation is to provide a framework that enhances the assessment reliability of the corrosion controlling factors. The framework is realized through the development of data-driven carbonation depth, chloride profile and hygrothermal performance prediction models. The carbonation depth prediction model integrates neural network, decision tree, boosted and bagged ensemble decision trees. The ensemble tree based chloride profile prediction models evaluate the significance of chloride ingress controlling variables from various perspectives. The hygrothermal interaction prediction models are developed using neural networks to evaluate the status of corrosion and other unexpected deteriorations in surface-treated concrete elements. Long-term data for all models were obtained from three different field experiments. The performance comparison of the developed carbonation depth prediction model with the conventional one confirmed the prediction superiority of the data-driven model. The variable importance measure revealed that plasticizers and air contents are among the top six carbonation governing parameters out of 25. The discovered topmost chloride penetration controlling parameters representing the composition of the concrete are aggregate size distribution, amount and type of plasticizers and supplementary cementitious materials. The performance analysis of the developed hygrothermal model revealed its prediction capability with low error. The integrated exploratory data analysis technique with the hygrothermal model had identified the surfaceprotection systems that are able to protect from corrosion, chemical and frost attacks. All the developed corrosion assessment models are valid, reliable, robust and easily reproducible, which assist to define proactive maintenance plan. In addition, the determined influential parameters could help companies to produce optimized concrete mix that is able to resist carbonation and chloride penetration. Hence, the outcomes of this dissertation enable reduction of lifecycle costs

International RILEM Conference on Materials, Systems and Structures in Civil Engineering Conference segment on Service Life of Cement-Based Materials and Structures

Vol. 2O volume I encontra-se disponível em: http://hdl.handle.net/1822/4341

Proceedings of the International RILEM Conference Materials, Systems and Structures in Civil Engineering segment on Service Life of Cement-Based Materials and Structures

Vol. 1O volume II encontra-se disponível em: http://hdl.handle.net/1822/4390