碱矿渣混凝土固-液相分析与介质传输机理研究

Due to the advantages such as low energy consumption and low carbon emission, it would make sense to reveal the mechanism of mass transport of alkali-activated slag (AAS) concrete. The project will promote application in engineering field and research of long term service performance for AAS concrete. In this project, research on chloride binding mechanism of AAS will be carried out firstly. Solid phases of C-(A)-S-H and hydration products of AAS will be characterized by TGA/DTG/DTA, XRD, FTIR, NMR and SEM-EDS. Based on the analysis of solid phase, the chloride adsorption and chemical combination of AAS will be studied quantitatively by applying thermodynamic theory. The mechanism of C-(A)-S-H adsorbing chloride will be investigated by molecular dynamics simulation consequently, too. Furthermore, the evolvement of alkalinity, composition and zeta potential of liquid phase of C-(A)-S-H and AAS, as while as the equilibrium mechanism between solid and liquid phases, will be investigated. Depassivation behavior of steel bars in the simulated pore solution of alkali activated slag will be also detected by electrochemical techniques. In this project, multi-scale test measures and actual marine exposure will be applied to investigate chloride and water transport performance in AAS systems. Based on phase and microstructure analysis of AAS, fractal theory and effective media theory will be applied to clarify transport mechanisms of chloride and water in AAS system. Eventually, a series of mass transport models of alkali-activated slag system on multi-scales will be established.

碱矿渣混凝土具有低能耗、低碳排放等优势，揭示碱矿渣混凝土的介质传输机理，对其推广应用和长期服役性能研究意义重大。本项目从碱矿渣氯离子固化机理研究入手，利用综合热分析、XRD、FTIR、NMR、扫描电镜等测试手段，分析C-(A)-S-H和碱矿渣水化产物固相特征，以此为基础，结合热力学理论研究碱矿渣吸附、结合氯离子性能；研究C-(A)-S-H和碱矿渣净浆对氯离子的等温吸附特性；结合分子动力学模拟，研究C-(A)-S-H的氯离子吸附机理；研究C-(A)-S-H和碱矿渣液相中碱度、化学成分和Zeta电位的经时演化规律以及固-液相平衡机制。基于电化学理论和试验，研究钢筋在碱矿渣模拟孔溶液中的脱钝机制。采用多尺度试验手段和实海暴露试验，研究氯离子和水分在碱矿渣混凝土中的传输性能。在微结构分析的基础上利用分形理论和有效介质理论，揭示碱矿渣混凝土氯离子和水分的传输机理，建立碱矿渣混凝土多尺度介质传输模型。

本项目对C-(A)-S-H 和碱矿渣水化产物进行了固相分析，获得了碱矿渣体系固相组成，阐明了碱矿渣体系的微结构特征；对C-(A)-S-H和碱矿渣净浆的孔溶液和氯盐浸泡液进行了液相分析，获得了碱矿渣体系液相中的碱度、化学成分和Zeta电位的经时演变规律。研究了C-(A)-S-H和碱矿渣净浆对氯离子的等温吸附特性，对氯离子固化中的物理吸附和化学结合进行量化分析，揭示了氯离子浓度、环境温度、碱度对碱激发矿渣胶凝体系氯离子固化性能的影响效应及机理，揭示了碱矿渣体系对氯离子固化的经时演变规律。发现水玻璃激发矿渣的氯离子固化能力大于NaOH激发矿渣，碱矿渣中氯化物的固化不仅包括物理吸附，还包括少量的化学结合，但氯离子在固化过程中的物理吸附占50%以上。基于模拟孔溶液试验和电化学理论，探明了碱激发矿渣体系中的钢筋脱钝机制。发现相同pH值条件下水玻璃激发矿渣模拟孔溶液中钢筋钝化膜的耐蚀性优于NaOH激发矿渣，相同pH值的水玻璃激发矿渣孔溶液有着更短的钝化膜生成时间。试验研究并揭示了碱矿渣混凝土毛细吸收水分、定水头压力水渗透以及湿扩散的水分传输规律；通过稳态扩散试验、氯盐自然浸泡、快速氯离子迁移试验和实际海洋环境暴露，研究了碱矿渣混凝土的饱和与非饱和氯离子传输性能，揭示了NaOH激发矿渣、水玻璃激发矿渣在水分、氯离子传输上差异表现的机理。本项目自主研发并完善了用于混凝土氯离子渗透性快速测定的交流电阻率法，该方法对碱矿渣混凝土有较好的适用性。开展了水和氯离子在C-S-H及C-A-S-H中传输行为的分子动力学模拟研究；探明了碱矿渣体系的水分和氯离子传输机理。