基于复合材料细观力学的水泥混凝土路面板早期裂缝演化规律研究

Early age cracking severely influences the capacity and durability of cement concrete pavement slabs. It is a frontier research topic on how to effectively control early age cracking in cement concrete pavement slabs. Currently, approaches are mainly phenomenal observations and empirical summarization when investigating early age cracking in cement concrete pavement slabs. So far, the mechanism of early age cracking is vague and needs to be investigated. The mesomechanics of composite materials is capable of describing the influence of flaws to the fracture behavior of cement concrete. The changes of temperature and moisture are two main factors that cause early age cracking in cement concrete pavement slabs. This proposal is aimed to reveal the mechanism of early age cracking in cement concrete pavement slabs. The damage and fracture behaviors of cement concrete pavement slabs will be focused under the thermo-hydro coupled environment. Based on the mesomechanics of composite materials and fractal theory, combined with meso- and macroscale testing technologies, the mesomechanical random aggregate models will be developed, which will be utilized to determine the thermophysical and mechanical properties of cement concrete. Then the proposed mesomechanical random aggregate model will be utilized to predict the residual stresses and early age cracking in cement concrete pavement slabs, which will be validated with the measured data in the cement concrete pavement slab casted in field. In the end, factors that influence early age cracking in cement concrete pavement slabs will be analyzed with the proposed models. And appropriate measurements will be proposed to decrease the early age cracking. The proposed research can be a theoretical basis for decreasing early age cracking and maintaining the capacity and durability of cement concrete pavement slabs.

早期裂缝严重影响水泥路面板承载力和耐久性。如何控制水泥路面板早期裂缝是水泥路面研究中的前沿课题。当前对早期开裂的研究多集中在宏观现象观察和经验总结上，而开裂机理有待进一步挖掘。复合材料细观力学可以描述细观缺陷对混凝土材料开裂行为的影响。温度、湿度变化是导致水泥混凝土路面板早期开裂的主要因素。本研究以揭示水泥混凝土路面板早期开裂机理为研究目标，以温/湿场耦合下水泥混凝土板损伤断裂行为为研究重点，以复合材料细观力学为理论基础，结合细观、宏观试验技术，融合分形理论，建立随机骨料细观力学模型，提出一套水泥混凝土的力学和热物性参数确定方法，继而预测水泥混凝土路面板内早期残余应力和早期裂缝的发展，并利用野外足尺试验验证所提模型。最后开展因素敏感性分析，提出降低水泥板早期裂缝措施。本项目的实施可以从细观层面上揭示水泥板早期裂缝发展规律，从而为降低水泥混凝土路面板早期开裂、提高承载力和耐久性提供理论依据。

本研究根据复合材料细观力学，首先建立水泥混凝土热膨胀系数预测模型，从材料角度设计出低温度敏感性的水泥混凝土。接着在试验室测试新浇筑混凝土的温度场、湿度场变化、温度收缩系数、湿度收缩系数等并观测其收缩开裂情况。建立细观力学有限元模型，预测路用水泥混凝土内部早期内应力发展和裂缝发展情况，揭示了水泥混凝土早期损伤断裂机理。然后修建足尺水泥混凝土板，监测浇筑后板内温度、板角翘曲，提出了计算水泥混凝土板硬化温度翘曲的正向计算方法，建立理论模型计算水泥混凝土内部早期固化温度翘曲应力，编写了基于ABAQUS的水泥混凝土路面温度场计算子程序和能够考虑拉压徐变差异的本构子程序，模型能够预测混凝土路面自浇筑后的温度场和应力场变化历史。最后，开展因素敏感性分析，提出降低水泥混凝土板固化温度翘曲应力，从而降低水泥路面板早期开裂的措施。研究发现：（1）骨料颗粒形状不会对水泥混凝土热膨胀系数产生显著影响；骨料的级配、类型，尤其是岩石种类对水泥混凝土热膨胀系数影响显著。（2）加入微/纳米火山灰后的水泥混凝土早期强度有所下降，后期强度发展较快，水泥混凝土早期水化进程放缓，温度和湿度变化降低，从而减小了水泥混凝土内部温度和湿度变化梯度，温度变形减小，微观结构更加致密，进而改善了水泥混凝土早期开裂状况。（3）可以从材料选择、配合比设计、浇筑时刻、养生方式、混凝土材料徐变性能改进、基层摩擦与板的尺寸等方面对硬化翘曲进行调节，从而降低水泥混凝土路面板开裂风险。本项目的实施可以从细观层面上揭示水泥板早期裂缝发展规律，从而为降低水泥混凝土路面板早期开裂、提高承载力和耐久性提供理论依据。