全组分废弃混凝土再生水泥熟料矿相匹配及烧成机理研究

With regards to the existing technical problems for the cementitious reusage of waste concrete in our country which lead to the low efficiency of various component separation in waste concrete, high production cost and large energy consumption, limited performance of recycled products, the technology roadmap of recycled cement from all components of waste concrete has been raised by the applicant to achieve the full and high value-added utilization of waste concrete resource. Based on previous work, analyzing the property of waste concrete's composition different from raw mineral of ordinary portland cement, the range of three modulus for raw meal and clinker of recycled cement will be investigated, the mineral match relationship and the sintering mechanism of recycled cement's clinker will be developed and clarified. Based on the ordinary raw meal, the effect of quartz sand and hardening cement paste in waste concrete on mineral match of clinker will be analyzed. The mineral match relationship and the suitable range of modulus for the recycled cement will be optimized. The effect of crystal SiO2 on clinker sintering will be verified. Based on phase transform process of harden cement paste in the process of high temperature, the reaction mechanism of clinker sintering will be established. The promoting effect of the additive compound of various industry waste residuals on the formation of clinker will be investigated, the influence mechanism will be analysed. On the basis of the above, the sintering mechanism of recycled cement's clinker will be established. The results of this research will provide valuable theoretical guides and basic experimental data for the cementitious reusage of waste concrete, and it will set up the fundamental basis for the optimization performance and practical applications of recycled cement.

针对我国废弃混凝土胶凝化再生利用技术存在的组分分离导致材料利用率低、生产成本和能耗高以及再生产品性能有限问题，提出利用全组分废弃混凝土制备再生水泥的新思路，以实现废弃混凝土资源的完全、高附加值再生利用。在前期研究基础上，从废弃混凝土成分区别于普通水泥生料的特点出发，探讨再生水泥生料、熟料的三率值范围、熟料矿相匹配关系，阐明熟料烧成机理。以普通生料为基准，分析废弃混凝土中硬化水泥石和砂中晶体SiO2对熟料矿相匹配的影响；探索适于再生水泥熟料烧成的矿相匹配关系，确定最佳率值控制范围。明确砂中晶体SiO2对熟料烧成的影响；基于硬化水泥石高温下的物相变化过程，分析其对熟料烧成的作用机理；研究复合掺杂工业废渣对熟料矿物形成的促进作用，分析其影响机制；在此基础上，探明再生水泥熟料的烧成机理。项目研究成果将为废弃混凝土胶凝化再生利用提供理论依据和基础试验数据，同时为再生水泥性能优化和实际应用奠定基础。

废弃混凝土胶凝化再生利用相关研究中多采用组分分离的办法，导致原材料利用率低、生产成本和能耗偏高、再生产品性能有限，本项目提出利用全组分废弃混凝土制备再生水泥的新思路。基于废弃混凝土区别于水泥工业原料的本质特点，研究了熟料矿相匹配、硅质原料中SiO2存在形式、硬化水泥石（HCP）高温下物相变化以及工业废渣复合掺杂对再生水泥熟料烧成及性能的影响。明确了再生水泥最佳率值控制范围、高结晶态SiO2和HCP对再生水泥熟料烧成的作用机制、工业废渣与氟硫矿化剂复合掺杂的最佳形式。基于我国现阶段建筑垃圾的组成特点以及废弃混凝土原料中MgO含量偏高的问题，研究了废弃粘土砖（WCB）对再生水泥熟料烧成的影响；以两种聚羧酸高效减水剂为例，研究了熟料中MgO含量变化对水泥与主流外加剂间相容性的影响。研究表明：高硅率（SM）、低铝率（IM）、高石灰饱和系数（KH）的匹配方案有助于再生水泥熟料烧成；1400℃煅烧温度下，再生水泥较适宜的率值范围为SM=2.4~2.8，IM=1.2~1.5，KH取0.95左右。提高废弃混凝土原料中SiO2的反应活性、降低其颗粒粒径，可显著降低再生水泥熟料烧成能耗，促进熟料中A矿的形成和发育；硅质原料的石英结晶度显著影响熟料矿物C2S的形成，对C3S形成影响较小。HCP对再生水泥熟料烧成有明显的促进作用；高温（T>1000℃）下，HCP内部主要发生固相反应，水泥主要矿物再次生成，未发现其它物相生成。钢渣、矿渣与氟硫矿化剂复合掺杂对再生水泥生料易烧性有良好的改善效果，有利于熟料中C3S形成；本项目试验条件下，复合掺杂的最佳形式为内掺3%钢渣或矿渣、外掺0.5%CaF2和1.31% CaSO4•2H2O。WCB对再生水泥生料易烧性有不利影响，但有利于促进熟料中A矿发育，提高再生水泥水化性能。MgO含量对水泥与聚羧酸高效减水剂相容性的影响与减水剂分子结构及掺量有关。本项目研究将为再生水泥的原料质量控制、科学配料、性能优化以及烧成机理研究提供理论参考和基础试验数据，同时为全组分废弃混凝土再生水泥技术的成果转化和实际应用奠定基础。