Performance Optimization And Application Study Of MCI Based On The Transport And Anti-corrosion Effciency In Concrete

The degradation of reinforced concrete structure under marine circumstance has become an important issue of common concern. How to inhibit the corrosion of steel bar for improve the durability of serving concrete structures is an unsolved issue right now. According to engineering practices, migrating corrosion inhibitor(MCI) is an effective methord to improving the durability of reinforfced concrete structures. However, for lack of the quantitative studies on expressing the penetrating performance of MCI in concrete and the relations between MCI amount and corrosion rate, the marketing application and composition design of MCI have been circumscribed.Based on the anticorrosion performance in Na Cl solution and the migrating performance in mortar of different composition designed MCI, a MCI(named PCI-2015) with good performance has been screened out. The tested nitrogen content of prism mortar speciman with water to cement ratio(W/C) of 0.55 at the depth of 70 mm is 702 mg/kg when PCI-2015 penetrating the speciman for 5d. The corrosion current density(Icorr) of steel bar in cube mortar specimen with W/C of 0.65 has reduced to less than 0.1 ?A/cm2 from 1.38?A/cm2 when PCI-2015 penetrating the speciman for 1d. The result of X-ray photoelectron spectroscopy for steel bars removed from concrete specimens demonstrated the chloride ion on the steel surface was replaced by molecules of the inhibitor. The results of thermogravimetric analysis and mercury intrusion method proved that PCI-2015 has reacted with cement hydration products(CH), the reaction products blocked the small holes(capillary pores) and refined pore size. The results of atomic force microscopy show that PCI-2015 molecules are absorbed on the surface of cabon steel sheet.Based on prior researches, a transport model of PCI-2015 has been built and verified. The PCI-2015 contents in the steel-mortar zone at different absorbing time are calculated by this transport model. The Icorr of steel bar in mortar contained different contents of Na Cl(0.25%, 0.5%, 0.75% and 1% wt. of cement) with three W/C ratios(0.45, 0.55 and 0.65) at different absorbing time are tested. By using multivariate nonlinear regression analysis, the relationship among the Icorr of steel bar, water-soluble chloride contents(Ccl) and the calculated mass concentration of PCI-2015 at steel-concrete interfacial zone(Cin) are established. And the application software has been developed for PCI-2015 repiring corroded steel in concrete.In this software, the PCI-2015 contents for decreasing the Icorr of steel bars to 0.1?A/cm2 in chloride contaminated cocrete are calculated. Based on the calculated results, the influence on steel corrosion rate by painted 200 g/m2 PCI-2015 on the surface of concrete with three water to binder ratios(W/B) and four different Na Cl contents has been studied. The results indicate that the Icorr of steel bar is reduced to less than 0.1 ?A/cm2 from the 3.833?A/cm2(steel bar in concrete with W/B ratio is 0.65 and 1% Na Cl) at 14 d until the end of 150 d test. The chloride diffusion coefficients of concrete painted PCI-2015 with three W/B ratios are reduced to 71.43%, 61.64 and 42.27% to unpainted one's, respectively. The anticorrosion efficiency and ability on improve chloride ions penetration resistance of concrete of PCI-2015 is better than MCI-A's. The protection and repair ability of painting PCI-2015 on chloride contaminated concrete in brine leaching and drying environment have been studied too. 3D scan technology has been used to remodel the steel bars in concrete. The results suggest that painted 400 g/m2 PCI-2015 and water-proofing agent on concrete can protect steel bar from corrsion in this environment.PCI-2015 has been used in a durable restoration project for a water conservancy aqueduct. A Gecor 8 online corrosion monitoring device is used to monitor the Icorr of steel bar in concrete before and after painting PCI-2015. The results show that the Icorr of steel bar in concrete after painting PCI-2015 for 150 d is reduced to 15% of the unpainted one's. The repaired ability of PCI-2015 is line with the standard requirements to meet project demands. The overall performance of PCI-2015 is better than another two foreign commercial MCIs. This is a low cost, less construction waste and sustainable way to improving the duraibility of reinforced concrete structures.