多年冻土区混凝土在冰-水-冰介质中早期强度增长规律及微观结构研究

o.Frozen state lasts for years, temperature is below 0 ℃ and contains ice crystals layers for permafrost. From the biggest frozen deep interannual variability can be divided into five sensitizing range in northwest area; The central area of northwest, and the area south Xinjiang,and the area north Xinjiang , Qinghai-tibet plateau, the east part of northwest China area. Because of filling pile concrete casting, concrete into the mold temperature, the hydration heat etc, can cause frozen soil of concrete pile in ice -water-ice of the special process of phase change, this process will in turn affect the initial strength of concrete. Subject to the northwest permafrost as the background, Study of frozen soil ice-water-ice migration rule and dissolve gather to influence hole structure of early concrete, draw a conclusion that the concrete piles microcosmic structure and the relationship between macro behavior; Study of hydration speed and pore water condensation ice of concrete condense time, internal structure change and strength of the stagnant, by concrete piles under negative temperature in area of permafrost, to make a numerical research conctete pile that in condensation and hardening process, and negative temperature environment, and mix proprotion, workability influence development strength of concrete, and concrete hydration heat and permafrost coupling, concrete performance development tendency; Through comprehensive study on concrete piles performance in area of permafrost,it is concluded that preparation technology satisfy the requirements of the concrete performance.

冻结状态持续多年，温度低于0℃且含有冰晶的土层为多年冻土。从最大冻深的年际变化上可将西北地区分为五个敏感区：西北中部区、南疆区、北疆区、青藏高原区、西北东部区。灌注桩混凝土浇筑后，混凝土入模温度、水化热等均会引起桩周冻土出现冰-水-冰相变的特殊过程，这一过程反过来又会影响混凝土的早期强度。课题以西北多年冻土为背景，从冻土冰-水-冰运移规律和溶解聚集时对早期混凝土孔结构的影响研究，得出灌注桩混凝土微观结构与宏观行为的关系；通过对多年冻土区混凝土灌注桩在负温下，其水化速度与孔隙水结冰对混凝土凝结硬化时间、内部结构变化和强度滞缓的研究，定量得出灌注桩混凝土在凝结、硬化过程中，负温环境、混凝土配合比、和易性等对混凝土强度发展的影响规律，以及混凝土水化热与冻土耦合作用时，混凝土性能发展趋势；针对冻土区灌注桩混凝土性能的综合研究，得出满足混凝土性能要求的配制技术。

本课题以西北多年冻土混凝土灌注桩为背景，依照试验测定的数据计算出持续低温环境（-３±１）℃、（３±１）℃及（１3±１）℃下水泥净浆的水化放热量随龄期增长的变化规律，探究在持续低温环境下的混凝土水化放热情况，通过混凝土水化放热量的定量分析，确定持续低温环境下的混凝土水化放热计算模型，并定量得出灌注桩混凝土在凝结、硬化过程中，负温环境对混凝土强度发展的影响规律，以及混凝土水化热与冻土耦合作用时，混凝土性能发展趋势；采用0.24、0.31级0.38水胶比对混凝土的强度、抗渗性、抗冻性进行了不同龄期及不同养护方式的研究，得出了强度的变化规律及耐久性劣化机理；采用压汞仪、孔结构分析仪、电子显微镜等仪器对早期混凝土孔结构的分析及研究，得出灌注桩混凝土微观结构与宏观行为的关系；对粉煤灰、磨细矿渣粉、硅灰以及引气剂、减水剂、防冻剂等外加剂的优化，采用适当的比例，改善混凝土内部胶凝材料体系的孔结构、改善浆-集界面结构，有效减少混凝土中泌水通道，从而减少混凝土的冻胀和开裂，并针对冻土区灌注桩混凝土性能的综合研究，对配合比进行技术优化。