基于钢筋锈蚀时变模型的氯氧镁水泥钢筋混凝土初裂时间

Initial cracking time of magnesium oxychloride cement reinforced concrete based on time-varying model of reinforcement corrosion

针对氯氧镁水泥混凝土中氯离子含量较高的问题,通过电化学试验研究了氯氧镁水泥混凝土中钢筋锈蚀速率的时变模型,并结合钢筋腐蚀电流密度以及理论模型,对氯氧镁水泥混凝土中钢筋的初始锈蚀时间和混凝土开裂时间进行预测.研究结果表明:裸露钢筋(S1)锈蚀速率符合幂函数型时变模型,BNC~水性涂层钢筋(S2)、Zintek涂层钢筋(S3)、Dacromet涂层钢筋(S4)和Geomet涂层钢筋(S5)锈蚀速率均符合对数型时变模型,Magni涂层钢筋(S6)锈蚀速率符合指数型时变模型.钢筋腐蚀电流密度限值可以作为氯氧镁水泥混凝土中钢筋初始锈蚀时间计算标准.S1,S2,S4和S6开始测试时已锈蚀,S3的初始锈蚀时间为1 115 d,S5的初始锈蚀时间为2 760 d;与S1相比,S2,S3,S4,S5和S6的混凝土开裂时间分别延迟了345,2 127,192,3 745和1 877 d,验证了氯氧镁水泥混凝土中涂层钢筋应用的可行性、长期稳定性和有效性.

Aiming at the problem of high chloride content in magnesium oxychloride cement concrete,a time-varying model for the corrosion rate of steel in magnesium oxychloride cement concrete was studied by an electrochemical test. Combined with the corrosion current density and the theoretical model,the initial corrosion time of steel in magnesium oxychloride cement concrete and the cracking time of concrete were predicted. The results show that the corrosion rate of exposed steel（ S1） is in agreement with the power function time-varying model： the corrosion rates of BNC coated steel（ S2）,Zintek coated steel（ S3）,Dacromet coated steel（ S4） and Geomet coated steel（ S5） are all in line with the logarithmic time-varying model,and corrosion rate of Magni coated steel（ S6） accords with exponential time-varying model. It is feasible to use the limit of the corrosion current density of steel as a standard for calculating the initial corrosion time of rebar in magnesium chloride cement concrete. S1,S2,S4 and S6 were corroded at the beginning of the test,and the initial corrosion time of S3 is 1 115 d and the initial corrosion time of S5 is 2 760 d. Compared with S1,the cracking time of S2,S3,S4,S5 and S6 is delayed by 345,2 127,192,3 745 and 1 877 d,respectively. The feasibility,the long-term stability and the effectiveness of the coated steel bar in the magnesium oxychloride cement concrete are verified.