Study On Electrodeposition Method For Repair Of Concrete Cracks

Electrodeposition method for repair of concrete cracks is a new technique. It is specially used for repair of those concrete structure with cracks which traditional techniques can not work or cost much money to repair them. In Japan and America, research was primarily investigated on the feasibility of electrodeposition method for repair of concrete cracks on land and partial properties of concrete with shrinkage cracks which has been repaired with this technique, while the technique has not been studied in our country. So the following aspects are studied systematically.1. Research on selection of electrolyte solutions was made, appearance of electrodeposits on the mortar surface and cracked part was compared, XRD method was used to analyse the electrodeposits. Results showed that :ZnSO₄, MgSO₄, MgCl₂ solutions can acquire better electrodeposition effect, and as to electrodeposition method for repair of concrete cracks the device adopted in the experiment is applicable.2. The factors influencing electrodeposition effect were investigated, the four parameters such as rate of weight gain, r,ate of surface coating, rate of crack closure and filling depth of crack were used to evaluate electrodeposition effect. SEM method was used to compare the microstructure. Results showed that accessorial electrode, electrode distance, concrete parameters such as water-cement ratio, cover depth, crack width and so on, concentration of electrolyte solution, electrical current density on the mortar surface and additive had a certain effect on electrodeposition effect.3. The effect of electrodeposition on BET surface area and microstructure of the mortar specimen was studied, different samples were taken out from the specimen which was 5mm, 20mm, 35mm away from electrodeposition surface, and COULTER SA3100 series surface area and por size analyzers were used to measure BET surface area and microstructure of the mortar specimen. Resultsshowed that at the point which was 5mm away from electrodeposition surface in the ZnSO₄ solution and 5mm, 20mm away from electrodeposition surface in the MgSO₄ solution, the total and different diameter range pore volume of the sample decreased, while the other points of the specimen remained unchangeable; the pore volume whose diameter was bigger than 20nm at the point of the specimen which was 5mm away from electrodeposition surface in the ZnSO₄ solution decreased greastest, while the total pore volume and BET surface area at the point of the specimen which was 5mm away from electrodeposition surface in the MgSO₄ solution decreased greastest.4. Carbonation of concrete after electrodeposition was investigated, andcarbonation depth at the cracked part and non-cracked part of the specimen was compared between electrodeposited specimen and non-electrodeposited specimen. Results showed that the property of resist-carbonation of the mortar specimen with cracks has increased, and if we use the MgSO₄ solution increase greater than the specimen which has been electrodeposited in the ZnSO₄ solution.5. Research on application of grey theory in electrodeposition method for repair of concrete cracks was studied, grey correlation theory was used to analyse effect degree of concrete parameters on electrodeposition effect , and carbonation depth of at the cracked part of the specimen after electrodeposition was presicted with Grey Model(l.l). Results showed that electrodeposition effect correlate with concrete parameters greatly, water-cement ratio has a greatest effect on rate of weight gain and rate of surface coating, while cover depth has a greatest effect on rate of crack cldsure; the precision of Grey Model(l,l) prediction is very high, and Grey Model(I,l) can predict carbonation depth at the cracked part of the specimen after electrodeposition.