Durability Research On Modern Concrete Exposed To Ocean Environment

Concrete structure has been widely used in various fileds of civil engineering(suchas construct, hydraulic structures, port engineering and traffic civil engineering) for itssuperior performance. However, because of many environmental factors such aschloride erosion, carbonation of concrete and so on, masses of concrete structures wereseriously damaged in early service life, and the costs of strengthening and rebuilding onconcrete structures are quite amazing. Now, the durability of reinforced concretestructure has been a hot topic in the international community, and scholars also havedone many researches on single-factor function of chloride erosion on concrete.However, it is complex to build and repair the reinforced concrete structures in oceanenvironment, in order to avoid the waste of manpower and material resource, theconcrete building structures in ocean environment should have longer service life,although the severely corrosivity on concrete structures from ocean environment madethis work hard. So, the study on concrete durability under ocean environment is along-term and complicated job. Much of the study on concrete durability was focusedon macroscopic aspect, actually, it is also important on microscopic study on concretedurability. In this text, a series of experiments were carried out about the resistance ofconcrete to chloride transport and the internal pore structure research of concretestructure, and make out the assess of the results of experiments, main study contents areas follow:[1] The environment that the experiments were mainly exposed to can be dividedinto three corrosive zones: air zone, tidal zone and underwater, in which, it is easy tocontrol the experiments for the different corrosive features of these three zones. Afterthe exposion of concrete specimens of different mix proportions to these three corrosivezones for1month,3months,9months and12months, the experiments to test chloridecontent of corroded concrete were carried out. Depending on the result achieved, theauthor assessed the resistance of concrete to chloride transportation through the results,and then analyzed the reasons for these results;[2] For the reason of the size limit of the concrete specimen, the long-term corrosion experiments cannot be continued, however,specimens of the same mixproportions with practical engineering, have been corroded in ocean environment formany years,were included,. By comparing and analyzing the data from experiments andpractical engineering, the changes of concrete’s performance after long-term corrosivefunction can be achieved;[3] Choose part of specimens of similar proportions to do mercury penetrationexperiment to test the pore structure distribution in concrete, XRD and XRFexperiments with neat cement paste of the specimens, then study concrete durabilityfrom microscopic view, so that the reliability of the results could be improved;[4] The wide use of high-performance concrete have drawn attention from theconcrete world, experiments were carried out to assess durability of the high-performance concrete used in Jiao Zhouwan subsea tunnel, and to offer theoretical basisfor its building.The results of the research demonstrate that: the corrosion extent of threedifferently corrosive areas in ocean is that:tidal zone> underwater> air zone, for theconcrete of the same mix proportion in the same corrosion zone, the deeper chloridecorrosion depth and the longer corrosion time, the more the surface chloride content ofthe concrete is; water to binder ratio has a great influence on the performance ofconcrete resistance to chloride:the bigger water to binder ratio, the worse resistance tochloride; the mineral admixture can effectively improve the permeability performanceof concrete resistance to chloride, but in order to get the concrete proportion of highquality, we need to control both mineral admixture and water cement ratiosimultaneously; by means of mercury penetration experiment, XRD and XRF, weobtained the same results as chloride testing experiment, making the macroscopicexperiments results with great power.