辅助性胶凝组分改善水泥石脆性的机理和优化

The annual output of cement in China reached 2.065 billion tons in 2011, including about 1.5 billion tons of cement clinker and 0.5 billion tons of Supplementary Cementitious Constituents (SCC, such as BFS, fly ash and et al). Previously, much attention has been played to solid wastes utilization, resources conservation, environmental protection and mechanical properties of cement and concrete with supplementary cementitious constituents. With the development of study during the last decade, the late age strength and durability of hardened cement paste are prove improved significantly by the addition of SCC. Additionally, some researchers found that the toughness of hardened cement paste can also be improved when the type, addition and fineness of SCC are suitable, which is a very significant field to the brittle cement material. However, the mechanism of toughness improvement has not been clearly revealed and illuminated, which leads to difficulty in further optimizing the toughness and other properties of hardened cement paste by designing the parameters of materials constituents. Then, the study will be focus on the effect of SCC on the toughness of hardened cement paste to clarify the mechanism of the fragility improvement of cement matrix with SCC and bring forward the optimization parameters of cement constituents. The results will provide theoretical and technical support for application of blended cement.

2011年我国的硅酸盐水泥产量已达20.65亿吨，其中水泥熟料产量约15亿吨，此外还添加了5亿吨以上的矿渣、粉煤灰等辅助性胶凝组分。以前，学者们仅从固体废弃物综合利用并兼顾强度等性能来看待辅助性胶凝组分。近10多年来通过辅助性胶凝组分对水泥石性能影响的深入研究，学者们发现这类组分不仅可节约资源，保护环境，还可提高水泥石的后期强度和耐久性。近年来有学者还发现，当辅助性胶凝组分的类型、数量和粒度适当时，可有效改善水泥石的脆性，提高其韧性，这对通常视为脆性材料的水泥石的工程应用来说难能可贵。然而这一研究尚处于起步阶段，其增韧机理尚不清楚，难以有目的地调控相关参数，进一步优化其性能。本项目拟在充分理解水泥和辅助性胶凝组分的水化硬化过程基础上，对复合水泥中辅助性胶凝组分有效改善水泥石脆性的机理开展深入研究，探讨其提高水泥石韧性的影响规律，提出性能优化的材料组合参数，为复合水泥的工程应用提供技术支撑。

水泥基材料是脆性材料，存在抗拉强度低、易收缩开裂等固有缺陷。因此，如何改善水泥基材料的韧性显得尤为重要，也是水泥基材料领域研究的热点和发展方向。本项目提出充分利用水泥熟料与辅助性胶凝材料的水化活性、水化产物组成和性能的差异，对水泥基材料组成、结构进行调控，获得如下主要研究成果：.（1）通过研究裂缝制造方法、裂缝深度、跨距、加载速率对断裂性能测试结果及误差的影响，建立了复合水泥浆体断裂性能表征方法，确定了断裂能测试过程中的各参数取值。.（2）参比水泥断裂能仅为46.4 N/m，硅酸盐水泥的断裂能为53.9N/m，而级配复合水泥的断裂能则高达70-80 N/m，最大时较硅酸盐水泥提高了49.7%，说明级配复合水泥的断裂韧性得到大幅度提高。.（3）研究了CH、AFt、C-S-H凝胶含量对水泥浆体断裂性能的影响，发现减少CH含量、适量的Aft及低钙硅比C-S-H凝胶可提高水泥浆体的韧性，未水化颗粒也可提高水泥浆体的韧性。.（4）采用HYMOSTRUC3D软件对水泥浆体的结构形成过程进行模拟，获得硅酸盐水泥和复合水泥BCF浆体不同时间的结构，同时采用Lattice方法对水泥浆体结构进行拉伸试验模拟。揭示了水泥浆体断裂韧性改善机理为：1）浆体中未水化矿渣、粉煤灰等颗粒数量增多，可作为阻碍裂缝扩展的介质，影响裂缝的扩展；2）在浆体中微集料含量大致不变的前提下，增大浆体中微集料的尺寸，增强了抵抗裂纹扩展的作用；3）级配复合水泥浆体中有害大孔减少、小孔增多，缓解了浆体中的应力集中现象。因此，级配复合水泥浆体的断裂性能得到了显著改善。