水泥基材料断裂性能与微孔结构研究

Fracture Properties and Micro-pore Structure of Cementitious Composites

以高掺量粉煤灰HDCC配合比为基础,测试了不同龄期基体的抗压强度、断裂韧度,同时采用MIP测试了其微孔结构.结果表明:养护28d主要改善基体大于50nm的大毛细孔结构,养护28d后再热养护7d主要改善其小于200nm的微孔分布,而养护28d后再继续热养护7d以上则仅仅改善其小于20nm的微孔分布,且改善效果不大;龄期、水胶比、粉煤灰品种及其掺量对基体抗压强度的影响大于它们对断裂韧度的影响,粉煤灰品种对抗压强度影响较大,但对断裂韧度的影响很小;断裂韧度与孔隙率的相关性大大低于抗压强度与孔隙率,如果在相关关系的拟合曲线中考虑小于20nm微孔含量的影响,则置信水平可大大提高.

Fracture toughness shows the ability to resist crack,and it is an important property of cementitious composites and design basis to high ductility cementitious composites（HDCC）.Compressive strength and fracture toughness at different curing age were measured,and also MIP were conducted,based on the mixture of matrix of HDCC with high content fly ash.Test results show that curing at the first 28d will mainly improve the macro-pore,hereafter chiefly improve the micro-pore.Effect of age,ratio of water to binder,types and content of fly ash on the compressive strength are higher than that on fracture toughness,the type of FA has more influence on the compressive strength than on the fracture toughness.The deviation of fitting relationship between the fracture toughness and porosity is also markedly lower than that of compressive strength.If the effect of micro-pore less than 20nm on the compressive strength or fracture toughness is considered,the confidence level of fitting curve markedly increases.