Development of the self-compacted and high-strength concrete for cold region

本研究的目的是研制适合寒冷地区的自密实高强混凝土，以减轻环境荷载。主要研究成果如下：(1)研制了适用于寒冷地区自密实高强混凝土的高效减水剂。通过改变温度，考察了高效减水剂的化学结构对混凝土的流动性、流动性保持性、水化缓凝性和高耐久性的影响。结果表明，接枝链长和短的异种接枝共聚物具有较高的水泥分散性和较低的水泥水化延迟率，而接枝链长的接枝共聚物既能满足混凝土的高流动性，又能满足混凝土在低温下的高耐久性。(2)研究表明，降低混凝土的自收缩对防止高寒地区自密实高强混凝土的开裂具有重要意义。提出了自密实高强混凝土配合比的预测方法，以便于在不同的粉料和骨料质量下进行混凝土配合比设计。从自密实的临界状态可以看出，粘结砂浆覆盖的粗集料的桥面结构牢固，且受粗集料浓度和砂浆流动性的影响较大。在此基础上，分别利用基于蒙特卡罗方法的概率模型和基于分形理论的概率模型，计算出混凝土满足自密实时粗骨料和细骨料的最大值和单位含水率(水粉比)。

This purpose of this study is to develop the self-compacting and high-strength concrete for the cold region to reduce an environmental load. Most important results are summarized as follwos :(1) We developed the superplasticizer for the self-compacting and high-strength concrete in cold region. The effect of the chemical structure of superplasticizer on the fluidity, fluidity retention, retardation of hydration, and high durability of concrete was examined when the temperature was varied. As a result, it was confirmed that the heterologous graft copolymer having a long and short graft chains shows highly cement dispersed and low retardation of cement hydration, and the graft copolymer containing longer graft chains satisfied both high fluidity and high durability of concrete at low temperature.(2) It was indicated that the reduction of autogenous shrinkage of concrete is very important to prevent cracking the self-compacting and high-strength concrete for the cold region. Moreover, it was imposed that both to control the ionic concentration of liquid phase in concrete and to containing a large amount of fly ash were able to decrease the autogenous shrinkage.(3) The prediction method of the mix proportion for the self-compacted and high-strength concrete was proposed in order to make concrete mix design easily when the quality of powder and aggregate were varied. The critical state of self-compactability could be asumed that the bridge structure of the coarse aggregate covered with adherent mortar firms and was influenced strongly by the concentration of coarse aggregate and the fluidity of mortar. Based on this assumption, the maximum values of both coarse aggregate and fine aggregate and the unit water content (water-powder ratio) when concrete was satisfied of the self-compactability could be calculated by using the probability model based on the Monte Carlo method and the fractal theory respectively.