多种因素对混凝土孔结构分形特征的影响研究

目的在分形理论的指导下,以压汞测孔为基础,探索混凝土结构形成条件与其分形特征,尤其是冻融循环后的混凝土孔隙分形特征.方法计算并分析了不同水化龄期下普通水泥和硫铝酸盐水泥孔隙分形特征的变化,研究了水泥熟料单矿物组成的孔隙分形维数.用压汞测孔的试验结果计算分析了混凝土冻融循环前后分形维数的变化.结果在180d以内水泥石的孔隙的分形维数随龄期增长而增大,在龄期为360d时,虽然总孔隙率最低,但由于水化物结晶度提高,凝胶孔含量降低,毛细孔增多,其分形维数变低;硫铝酸盐水泥水化3d～14d期间,分形维数不断增高,28d维数回落,与硅酸盐水泥长龄期的特征一致.结论在水泥熟料单矿物水化硬化孔分布特征评价中,其分形维数大小顺序为C3S>C2S>CF>C3A.C40强度等级的混凝土和C60非引气混凝土冻融循环200次后与受冻前孔隙分形维数相比有明显的变化,C100非引气混凝土冻融循环1200次后,其分形维数有明显的变化,而引气后的C60混凝土经1200次冻融循环后,其分形维数无明显变化.此外,养护条件对水泥石孔隙分形特征也有明显的影响.采用分形理论分析评价多种因素对混凝土孔结构分形特征的影响是十分有效的.

Research of High Resistant Freezing Fly Ash Pumping Concrete in Ocean Engineering

If ordinary strength fly ash pumping concrete can be used for ocean engineering in chilling area,its properties will be improved greatly.In this paper,the effect of concrete air amount with Fly ash ignition loss is tested and analyzed,a new air entraining agent for fly ash concrete is exploited,and the differences of fly ash concrete before and after pumping are tested.High resistant freezing ordinary strength fly ash pumping concrete is studied,and it is applied to harbor engineering and bridge construction along the ocean.The result shows that,for common air entraining agent,the effect of concrete air amount caused by fly ash ignition loss is notable.If ignition loss is higher than 6%,in order to make the same air amount,air entraining agent will need 5 times amount.And the loss of concrete air amount is very notable in construction.Thus,high resistant freezing ordinary strength fly ash pumping concrete needs special air entraining agent.In order to make up ordinary strength fly ash pumping concrete having high resistant freezing with seawater,as a controlling index,air amount of concrete after pumping is higher than 5%,otherwise the freezing breakage characteristics of concrete test specimen is notable.