Development and Evaluation of High-durable Concrete in Ice Sea Region

1. 海水对混凝土冻损机理的影响差示扫描量热法研究表明，浸泡在海水中的混凝土的吸热曲线比浸泡在淡水中的混凝土的吸热曲线宽。试件在海水中的解冻温度分布随着时间的推移而变宽。浸泡在海水中的试样，随着老化的进行，孔隙的数量越来越多，孔径可达数万至数千纳米。总孔隙体积也要大得多，所以在海水的情况下，冻结水的数量增加。这说明混凝土浸在海水中容易发生冻损。基于可靠度理论的混凝土劣化预测为了验证基于可靠度理论的混凝土结构劣化预测，我们对混凝土速冻融试验、暴露试验和砂浆抗拉强度试验数据进行了分析。结果表明，水灰比越低，可靠性越高。在可靠性指标为75%、95%等情况下，可按时间估算混凝土结构的使用寿命和维修计划。水下抗冻混凝土的抗冻性能引气剂与含纤维素的抗冻掺合料等特种掺合料共同使用，难以在混凝土中形成合适的空隙体系。引入塑料微球（EPM）代替引气剂，以纤维素醚为抗冻水掺合料提高水下抗冻水混凝土的抗冻性能。结果表明，掺1.0% EPM和60%细度为8000g /cmTAU12@E14的高炉矿渣可提高混凝土的抗冻性能。在寒冷气候下暴露在海水中的大型混凝土试件的劣化大约有50个大型试件，每个大约有2到3倍的重量，在日本北海道的海边暴露了十年，以阐明材料、混合比例和其他因素对霜冻损害的影响。不同部位或混合比例的试样，其结垢程度不同。冻融循环次数多或饱和度高的部位，结垢现象严重。少

1. Mechanism of Frost Damage of Concrete Effected by SeawaterAccording to differential scanning calorimetry, the endothermic curve of specimens immersed in seawater is broader than that of specimens in fresh water. The thaw temperature distribution of specimens in seawater widens with time.A specimen immersed in sea water has greater number of pores of size several ten to thousand nm as aging proceeds. The total pore volume is also much higher, so the amount of frozen water increases in the case of sea water.These indicates that concrete immersed in seawater is easily subject to frost damage.2. Deterioration Prediction of Concrete by Reliability TheoryTo examine deterioration prediction of concrete structure by reliability theory, we analyze the data of concrete specimens during rapid freeze-thaw tests and exposure tests, and mortar specimens during tensile strength tests.From these examinations, we conclude that when the water cement ratio is low, the reliability is high. The service … More life and repair plan of concrete structures can be estimated as time on index of reliability 75%, 95%, etc.3. Frost Resistance of Antiwashout Underwater ConcreteIt is difficult to form a suitable air-void system in concrete in which air-entraining agents and sonic special admixture, such as antiwashout admixtures containing cellulose, are used together.We have introduced plastic micro-spheres (EPM) instead of air-entraining agents to improve the frost resistance of antiwashout underwater concrete with cellulose ether as an antiwashout admixture. As a result, frost resistance of concrete is improved with the addition of 1.0% EPM and 60% blast-furnace slag with fineness of 8000 g/cmTAU12@E14. Deterioration of Large Concrete Specimens Exposed to Seawater in Cold ClimateAbout fifty large specimens, each have about two or three tf in weight, have been exposed at the seashore in Hokkaido Island, Japan for ten years to clarify the effect of materials, mix proportions and others on the frost damage.The degree of the scaling is different by the parts or the mix proportions of specimens. The scaling occurred severely at the position of the specimens which were exposed to more freezing and thawing cycles or were at high degree of saturation. Less