预处理SAP在水泥基材料中的成孔机理及其对性能影响的研究

Surfactant air entraining agents are widely utilized in cement-based materials to form air voids which improve the frost resistance significantly. However, there are usually some urgent problems during the air entraining process using this kind of agents, such as fluctuate air content and unsteady air voids structure. In this research, a new trial to form air voids within the cement-based materials using pretreated Super Absorbent Polymers (SAP) as the primary materials and will be carried out, and the mechanism will be investigated comprehensively. Studying the principle of the water absorption-releasing of SAP, proper types of SAP and and pretreating agents will be selected while the pretreatment process will be made. In addition, the strucuture and characteristics of air voids formed by pretreated SAP will be investigated deeply with the micro-analysis. After the effect of pretreating agents on hydration of cement and the effect of pretreated the SAP on internal relative humidity within cement-based materials are investigated, the water-released principles or characteriastics of pretreated SAP within the cement paste and the mechanism of air voids forming will be obtained. Furthermore, the effect of the strucuture and characteristics of air voids formed by pretreated SAP on the performances of the cement-based materials, such as main mechanical behaviours, frost-resistance, impermeability and shrinkage deformation, will be researched, and their relations with air voids structure will be given. At last, a kind of air-entraining technique which is able to design and control the air voids sturcture in cement-based materials will be acquired, and it will improve the durability of cement-based materials, especially the forst resistance and impermeability, due to the both effects of air entraining and internal curing. The results and conclusions of this research will be not only significant to complement the deterioration mechanism of concrete due to the action of freeze-thaw and enhance the performances of the cement-based materials, but also will provide an new idea and relevant theoretical foundation for further research of the multifunctional concrete admixtures.

针对表面活性剂型引气剂在水泥基材料中引气时存在的含气量波动大、气孔结构不稳定等问题，本研究采用吸水树脂SAP作为主要材料，探索一种新的"引气"机制。通过研究SAP的吸、释水规律，优选SAP品种和预处理试剂，确定预处理方法；采用微观分析手段，表征预处理SAP形成的气孔特性和气孔结构，结合预处理试剂对水泥水化的影响和预处理SAP对水泥基材料内部相对湿度的影响，分析其在水泥石中的释水特征与规律，探究气孔形成机理；研究预处理SAP形成的气孔特性与气孔结构对混凝土的主要力学性能、抗冻性、抗渗性、收缩变形性能的影响及关系。获得一种可以设计和控制水泥基材料中气孔结构的"引气"技术，利用预处理SAP引气和自养护的双重作用效果，提高水泥基材料的抗冻性和抗渗性等耐久性能。不仅对完善水泥基材料冻融破坏机理，提高水泥基材料的综合性能具有重要意义，而且为研究新型多功能混凝土引气剂提供新的思路并奠定相应的理论基础。

水泥基材料的抗冻性是重要的耐久性问题之一，引气技术是提高水泥基材料抗冻性的一项有效措施，但表面活性剂型引气剂在应用时存在着含气量波动大、气孔结构不稳定等问题。本研究采用吸水树脂SAP 作为主要材料，使其在不同溶液中预吸水后掺入水泥基材料，利用SAP颗粒形成孔隙，探索一种新的"引气"机制。主要测试了SAP的吸释水特性并确定了预处理方法，对预处理SAP 颗粒形成的孔隙特性和孔隙结构进行了表征，研究了SAP颗粒粒径范围、掺量、预处理剂品种和掺加方式对水泥石孔结构和气孔结构的影响规律，研究了预处理SAP 对混凝土性能的影响。.结果表明：不同品种SAP在不同液体中的吸水率相差较大，吸水率适中且释水速率较慢的SAP适用于水泥基材料中；低浓度（<30%）的有机硅溶液和饱和硬质酸钠溶液可以用作预处理剂。SAP掺入后增大了1d~7d龄期内水泥石的水化程度，而预吸有机硅溶液和预吸饱和硬脂酸钠溶液的SAP的这一作用时间较长。采用压汞法对水泥石孔结构的研究表明：掺量为水泥用量的0.1%、0.2%及0.4%时，SAP降低了水泥石的总孔隙率，且在掺量0.2%时产生了气孔尺寸的孔隙，气孔尺寸的孔隙大小与SAP颗粒粒径成正比，但SAP颗粒粒径过大时并不能形成气孔(>87μm)，预吸饱和硬脂酸钠溶液及预吸有机硅溶液的SAP降低了水泥石的孔隙率，但预吸饱和硬脂酸钠溶液的SAP有效地形成了气孔尺寸的孔隙。对气孔结构的测试也表明SAP掺入水泥净浆和混凝土都具有引气效果，中等颗粒粒径的SAP引气效果明显，气孔数量增加，气泡平均半径减小。.掺加预处理SAP的混凝土抗渗性有所提高，特别是经过有机硅处理的SAP作用明显。SAP以适宜的掺量掺入时可以提高混凝土的抗冻性和抗盐冻性能。中等粒径范围的SAP对混凝土性能的提高幅度较大。预吸有机硅溶液的SAP提高了混凝土的抗盐冻性能，但对抗冻性没有显著作用；而预吸饱和硬质酸钠溶液的SAP可以改善混凝土的抗冻性。随着SAP掺量的增加，同一龄期混凝土的自收缩率呈现逐渐降低的趋势，距干燥面同一距离处的混凝土内部相对湿度增加，体现出SAP的自养护效果。.选取吸水率和释水速率适宜的SAP，并控制其颗粒粒径范围及掺量，掺入水泥基材料可以提高其抗冻性和抗渗性等耐久性能。对提升寒冷地区混凝土的性能具有理论参考价值和实用指导意义，同时对研究新型多功能混凝土引气剂提供理论参考。