Modeling and Simulation of Electromutagenic Processes for Multiscale Modification of Concrete
Concrete contains numerous pores that allow degradation when chloride ions migrate through these paths and make contact with the steel reinforcement in a structure. Chlorides come mainly from the sea or de-icing salts. To keep the reinforcement from being exposed to chlorides, it is possible to electrokinetically force nanoparticles into the pores, blocking access. This procedure is called electrokinetic nanoparticle treatment. When the particles used are reactive in nature, the process becomes both structural and chemical in nature. We use the term electromutagenic processing to describe such extensive electrochemical remodeling. Filling the pores in a block of concrete with solid materials or nanoparticles tends to improve the strength significantly. In this paper, results obtained from modeling and simulation were aimed at multi-scale porosity reduction of concrete. Since nanoparticles and pores were modeled with spheres and cylinders having different sizes, the results were compared with traditional sphere packing problems in mathematics. There were significant differences observed related to the sizes of spheres and allowable boundary conditions. From traditional sphere packing analysis the highest porosity reduction anticipated was 74%. In contrast, the highest pore reduction obtained in this work was approximately 50%, which matched results from actual electrokinetic nanoparticle treatments. This work also compared the analytical and simulation methods used for several sizes of nanoparticles and pores.
Crack closure of reinforced concrete by electrodeposition technique
Abstract The electrodeposition method for rehabilitation of cracked reinforced concrete, based on the electrochemical technique, is presented here. Investigations on reinforced concrete beams of size 15×15×125 cm were conducted in this study. Specimens cracked by chloride attack for 18 months were immersed in a ZnSO 4 solution, and were applied with a constant current for 8 weeks. The development of crack closure due to the precipitation of electrodeposits (ZnO) was evaluated. Water permeability, chloride ion concentration, polarization curve and half-cell potential were measured in order to assess the effectiveness of this method in the improvement of concrete properties. The results indicate that electrodeposits formed on the concrete surface were able to close the concrete cracks and to decrease the concrete permeability. In addition, the investigation shows that the application of electrodeposition have effects on the desalination of concrete and re-passivity of the reinforcing steel in concrete.
USE OF ELECTRODEPOSITION FOR REPAIR OF CONCRETE WITH SHRINKAGE CRACKS
The electrodeposition method for repair of cracked reinforced concrete is presented here. Electrodeposition means precipitation of material on the surface of an electrode by electrolysis. The ultimate purpose of this study is to apply this technique to land-based reinforced concrete structures. Investigations on mortar specimens with embedded steel were conducted. After cracking the specimens with a specified load, they were immersed in several types of solutions. Then a constant current between the embedded steel in mortar and an electrode in the solution was applied. The deposition pattern on the surface, the crack closure development, and surface coating due to the precipitation of electrodeposits were checked and evaluated. In order to assess the effectiveness of this method to improve the mortar surface, water permeability, pore size distribution, and adhesion strength were measured. The results indicate that electrodeposits formed on the mortar surface are able to close the crack and coat the mortar surface. In addition, the investigations show that the deposition product can improve the microstructure of the mortar surface.