Department of Mechanics: Seminar: Abstract Travnicek 2019

From Wiki @ Department of mechanics
Jump to navigation Jump to search

Transport of chlorides in reinforced concrete

Pavel Trávníček, Post-doctoral Researcher, Department of Mechanics, Faculty of Civil Engineering, CTU in Prague

Department meeting room (B-366), Faculty of Civil Engineering, Czech Technical University in Prague

Thursday, 26 March 2019, 15:00-16:00

Concrete structures are subjected to a number of environmental deteriorating effects due to the concrete pore system that creates a pathway for other elements such as chloride ions to penetrate into the material. Due to the presence of steel in the majority of the concrete structures, the system is prone to a corrosion process initiated when certain criteria are met, such as reduced alkalinity of the cementitious material. Complexity in a concrete mixture composition along with different curing methods and various surface treatments results into a different penetration resistance creating a need for numerical models backed up by experiments.

For the diffusion analysis, a diffusion coefficient must be known for a successful durability prediction and the key parameters and their effect on the derived parameter must be quantified. The diffusion coefficient can be effectively derived from a chloride concentration profile ingressed into the sample by means of natural or electro-migration. Advatages and possible disadvantages of both are discussed.

Parameters such as boundary concentration evolution, binding, aging and skin effect, and chloride adsorption are discussed with respect to their impact on derived average diffusion coefficient. The experiment stands on natural diffusion through sound concrete samples of different w/c ratio and content of fly ash.

Majority of structures contain cracks and their effect of the diffusion must be understood. Cracks can be viewed as individual large pores driving the chloride deeper into the material much faster than compared to actual pores, that are in their nature constructive and tortuous thus increasing the total path needed for an ion to pass. An approach of simulation of chloride ion ingress into the damaged structure modeled by a continuum is presented. Finally, a note on chloride removal along with re-passivation of steel reinforcement is also given.