新型绿色水泥LC3-再生骨料混凝土水化机理与性能优化提升的多尺度试验研究与数值模拟

In order to reduce the environmental burden caused by the high energy consumption and high pollution of cement industry, to alleviate the pressure of natural gravel resources, and to promote the recycling of waste concrete existing in construction and demolition waste, this project innovatively propose to replace the traditional cement with the Limestone Calcined Clay Cement (LC3) and to substitute recycled aggregate for natural aggregate so as to obtain the LC3 recycled concrete that can achieve the complementary advantages of the two materials and also contributes to the sustainable utilization of resource. This work starts by the microstructural study of LC3 gel and investigates the influence of LC3 hydration products and pore distribution on the mechanical properties of the gel by combining the experimental analysis with the hydration modeling method. The obtained mechanical parameters at microscopic scale will be put into the mechanical model at mesoscopic scale; the nanoindentation test as well as the hydration modeling of the new and old interfacial transition zones existing in recycled concrete are carried out simultaneously. The obtained mechanical properties at mesoscopic scale as well as those of transition zones will be put into the mechanical model at macroscopic scale. Thus, a multiscale numerical model that connects the structural features and mechanical characteristics of the microscopic, mesoscopic and macroscopic levels could be established. The numerical results are then verified with the experimental tests carrying out at the three scales. The goal is to achieve the optimization design as well as the prediction of the microstructure and mechanical properties of concrete and to provide theoretical support and scientific basis for the development and application of LC3 recycled concrete.

为减少高能耗、高污染的水泥行业带来的环境负担，缓解天然砂石资源紧缺，促进建筑垃圾中废混凝土的回收利用，本项目创新性地提出了采用石灰石与煅烧粘土复合胶凝材料（LC3）代替传统的水泥，再生骨料代替天然骨料，配制出既能实现两种材料优势互补又能促进资源可持续利用的LC3再生混凝土。课题从分析LC3凝胶体的微观结构入手，结合试验研究和水化模拟，分析LC3水化产物与孔隙分布对凝胶体力学性能的影响。将微观尺度的力学参数输入到细观层次的力学模型中，并开展考虑再生混凝土新旧界面过渡区的纳米压痕试验和水化模拟研究。将细观尺度的力学参数与界面区的力学参数输入到宏观层次的数值模型中，建立联系材料微观（凝胶体）-细观（砂浆）-宏观（混凝土）结构特征与力学性能的多尺度数值模型。通过与三个尺度上开展的力学性能试验相校核，实现对混凝土微观结构和力学性能的优化设计与预测，为LC3再生混凝土的发展应用提供理论支撑和科学依据。

为减少高能耗、高污染的水泥行业带来的环境负担，缓解天然砂石资源紧缺，促进建筑垃圾中废混凝土的回收利用，本项目创新性地提出了采用石灰石与煅烧粘土复合胶凝材料（LC3）代替传统的水泥，再生骨料代替天然骨料，配制出既能实现两种材料优势互补又能促进资源可持续利用的LC3再生混凝土。低碳低能耗的LC3与再生混凝土结合可在微观尺度上优化水化产物分布，细化凝胶体的孔径；在细观尺度上，LC3凝胶体系提高了再生混凝土基体的密实性，增加了新旧界面区凝胶材料的比重，降低了界面区的孔隙率，提升了界面区的力学性能；在宏观尺度上，LC3提升了再生混凝土的强度和耐久性。根据既定的年度研究计划及进度安排，本项目系统地研究了不同掺量的石灰石粉和煅烧粘土对LC3凝胶体水化机理的影响研究，分析了LC3胶凝体系对再生混凝土界面区的改性提升，建立微观水泥水化特征与再生混凝土宏观性能的联系。首先，开展了LC3凝胶体的水化产物化学组分分析的试验研究，从测试分析的角度研究不同组分的LC3在水化进程和水化产物特征等方面差异，并与普通硅酸盐水泥的水化过程进行对比分析。然后，开展了LC3再生混凝土的微观结构、力学性能和抗氯离子渗透性能研究，分析了LC3掺量对再生混凝土的改性提升机理。最后，开展了包裹改性再生骨料混凝土的微观结构与破坏特征研究，分析了纤维增强包裹层对再生混凝土界面区的提升作用，探究了增强层阻隔裂缝开展与传递的作用机理，发现了改性组中混凝土的损伤总量在整个加载过程中均低于未改性组。LC3与再生混凝土的结合既缓解了天然骨料供应的压力，解决了拆除建筑废弃物的占地和环境污染问题，又促进了水泥产业向节能减排绿色发展模式的转变，LC3再生混凝土技术将会是未来的重要发展趋势。