Preparation Of Loaded Lauric Acid-imidazoline Rust Inhibitor And Investigation On Protective Performance Of Reinforced Cement-based Materials

It is well accepted that steel corrosion is one of the prime reasons influencing the durability and service life of the reinforced concrete structures.Among numerous concrete reinforcement protection methods,incorporation of organic corrosion inhibitors has been acknowledged as an effective method to inhibit the corrosion damage of steel.However,the limitations of conventional organic corrosion inhibitors restrict its application in reinforced concrete structure,e.g.degradation of long-term resistance to corrosion due to the evaporation of inhibitors through the concrete pore system,leaching of toxic elements,environmental pollution and adverse effect on the setting,strength and durability of the resulting concrete.Lauric acid-imidazoline(LAI)is an environmentally friendly corrosion inhibitor with excellent performance used in the protection of metal equipment in the oil and gas industry,due to their superior corrosion resistance properties and low toxicity to the environment and human body.However,study on the application of such corrosion inhibitor in reinforced concrete is rare.Based on the previous studies of our research group,the present study aims to use LAI as corrosion inhibitor,and the feasibility of its application in reinforced concrete structures and its corrosion resistance performance are explored.The research works are mainly as follows: influence of LAI in the macroscopic and microscopic properties of fresh and hardened cement;the reaction mechanism between LAI and hydraulic cement;preparation process of a feasible modified zeolite supported LAI as corrosion inhibitor for addition in cement matrix.The effect of concentration,particle size,modification conditions and pore structure on zeolite in loading LAI is studied,and the influence of zeolite supported LAI in the corrosion behavior of steel bars also investigated in the reinforced mortar specimens.The experimental results in this work are summarized as follows:(1)LAI can promote the early hydration reaction of cement,attributed to the bubbles introduced by LAI in the fresh paste and hence increasing the fluidity and prolonging the setting time of the resulting fresh paste whereas decreasing the mechanical strength of the hardened cement paste.(2)Concentration of the LAI,acetone solution and particle size of zeolite influence the loading capacity of LAI on zeolite to some extent.When the mass concentration of the LAI acetone solution is 2.0% and the particle size of zeolite is in the range of 0.0385 mm to 0.074 mm,the natural zeolite achieves the optimal supporting rate(up to 2.39%).The pore structure of Ca-Zeolite,Na-Zeolite,and K-Zeolite were significantly improved,corresponding to the LAI loading capacity of 14.09%,12.23%,and 7.40% at atmospheric pressure,and is 5.90 fold,5.12 fold,and 3.10 fold higher as compared to the unmodified zeolite,respectively.The vacuum loading environment is also favorable for the loading capacity of zeolite.For instance,the loading capacity of Ca-Zeolite is increased from 14.09%(normal pressure)to 16.40%(vacuum loading environment).(3)The influence of zeolite supported LAI on the corrosion behavior of steel bars also investigated.When the steel reinforced cement mortar was immersed in 3.5% NaCl solution,the initial corrosion time of the steel of the zeolite supported LAI incorporated mortar was delayed by 86% as compared to the control mortar,and the corrosion current density was also reduced with assistance to the introduction of zeolite supported LAI.After being immersed in the NaCl solution for 142 d,the corrosion inhibition efficiency of zeolite supported LAI was 90%.(4)The corrosion inhibition mechanism of zeolite supported LAI on steel was revealed.In steel reinforced mortar,the inhibition mechanism of zeolite supported LAI is related to the following two reasons:(a)improvement of pore structure of the resulting cement matrix.On one hand,air entrance resistance capability of mortar incorporating zeolite supported LAI was improved compared with the mortar directly incorporating LAI,on the other hand,the incorporation of zeolite as a fine aggregate can refine the pore structure of mortar and hence reducing the penetration of chloride ions and delaying the corrosion initiation time of steel reinforcement.(b)adsorption of LAI.LAI can migrate to the surface of steel and thus inhibiting the corrosion rate of the steel.