导电混凝土在寒冷与硫酸盐-氯盐腐蚀环境下的长期稳定性研究

The damage in conductive concrete may be induced by corrosion chloride ions and sulfate ions, freezing and thawing cycle, as well as alternation of wetting - dry in serious corrosion environment. Such a damage may not only lead to the degradation of mechanical properties, but also affect the long-term stability of conductive behavior. Based on the correlation between damage evolution and variation of potential barrier among conductive inclusions, the effect of damage due to serious environment on the resistivity of conductive concrete is investigated, and a new high-strength concrete with long-term stability in serious corrosion environment is designed. First, the serious environment is simulated by designing corrosion system, such as corrosion by solution, freezing and thawing cycle, as well as alternation of wetting - dry, and go and return in following a circle. The damage evolution and resistivity variation of conductive concrete is detected by ultrasonic technique and electrical measuring method. Secondly, the nucleation mechanism and growth behavior of micro-cracks of the material in serious environment is theoretically analyzed, and the relation between speed of damage evolution and chemical reaction rate is established. Thirdly, the damage of conductive net caused by micro-cracks is investigated, and a new model for describing the relation between damage induced by serious environment and resistivity variation is proposed. Based on experimental study and theoretical analysis, a new conductive concrete is finally designed by adding some suitable mineral additions and water reducer, such a high-strength concrete possesses long-term stability in serious corrosion environment.

导电混凝土因氯盐和硫酸盐的侵蚀、冻胀和干缩等因素共同作用而产生损伤，它既导致导电混凝土的力学性能的劣化，又影响其电学性能的长期稳定性。本项目以损伤演化与导电相之间势垒增加之间的关联关系为研究的基本出发点，探究环境所致损伤对导电混凝土电阻率的影响机理，开展具有长期稳定性的导电混凝土的材料改性设计。首先采用模拟严酷腐蚀环境，设计溶液侵蚀-冻融循环-干湿交替的腐蚀制度，开展导电混凝土损伤演化和导电性能衰变的实验研究；其次从理论上研究在严酷环境下损伤的成核机理和长大规律，探究统计损伤速度与化学反应速率之间的关联关系；然后探讨损伤如何导破坏导电混凝土内部的导电网络，由此建立环境所致损伤-电阻率变化模型。在实验研究和理论建模分析的基础上，通过对导电混凝土材料体系添加合适的矿物掺和料和减水剂的方法，研制在严酷环境下具有长期稳定性的高强导电混凝土。

在寒冷与硫酸盐腐蚀的严酷环境下，导电混凝土，无论是作为融冰化学功能材料，还是用于传感器的机敏材料，都存在长期使用的性能稳定性问题。本项目针对性地开展了三方面的研究：1）冻融循环下材料稳定性的研究。揭示了导电混凝土在冻融循环下电阻增加的机理；建立了基于冻融循环次数的电阻率演化模型；发现了压阻稳定性与冻融循环次数近似服从指数衰减规律。2）基于损伤力学的氯离子传输力学-化学理论体系的研究。提出了一种考虑化学反应、物理吸附、持续水化作用和损伤演化的氯离子快速迁移测试理论模型，揭示了在混凝土中基于损伤力学的氯离子传输机理，建立了侵蚀性离子传输的化学—力学耦合理论3）材料配方的优化设计。设计了在导电混凝土中复掺不同比例的粉煤灰和硅灰，分别研究导电混凝土在硫酸盐腐蚀、硫酸盐腐蚀和干湿交替的耦合作用、冻融循环三种环境下的抗腐蚀能力，据此，选出了较优的粉煤灰和硅灰的配合比结果。项目研究成果对于导电混凝土的材料设计与分析有重要的指导作用。