超高性能水泥基复合材料早期自收缩特性研究

Study on Early Autogenous Shrinkage of Ultra-High Performance Cementitous Composite

采用新型高精度全自动自收缩测量仪，研究了加入粗集料、不同水胶比（mw／mB=0．16，0．20，0．24）和不同钢纤维体积分数（φf=0％，1％，2％，3％）对超高性能水泥基复合材料（ultra—highperformancecementitouscomposite，UHPCC）自加水起33h内自收缩特性的影响．结果表明：UHPCC早期自收缩随龄期的发展具有明显的双阶段特征，即初始快速发展阶段和后期缓慢发展阶段；UHPCC早期自收缩随着水胶比的降低而增加，当水胶比从0．24分别减小到0．20，0．16时，0～20h内其自收缩值分别增加了34．09／6和63．8％；粗集料和钢纤维对UHPCC早期自收缩有明显的抑制作用，钢纤维体积分数从0％分别增至1％，2％和3％时，0～33h内其自收缩值分别降低了23．9％，60．5％，86．5％；UHPCC在33h时的自收缩值与水胶比（≤0．24）、钢纤维体积分数（0％～3％）这两者的关系均近似呈线性相关．

The study on early autogenous shrinkage is an important method to predict early crack of cemen- titous materials with low water-binder ratio. The novel automatic apparatus with high-precision was used. The influence factors influencing early autogenous shrinkage of ultra-high performance cementitous com- posite（UHPCC）, which include coarse aggregate, different water-binder ratios, different volume fractions of steel fiber, were investigated. The results show that two stages can be clearly identified during the early autogenous shrinkage process of UHPCC. rapid development stage and slow development stage. The early autogenous shrinkage of UHPCC increases with the decrease of water-binder ratio. The autogenous shrinkage in 20 h increases by 34.0% and 63.8% respectively when water-binder ratio decreases from 0.24 to 0.20, 0.16. Coarse aggregate and steel fibers have great positive effects on the autogenous shrinkage of UHPCC. The autogenous shrinkage in 33 h decreases by 23.9%, 60.5% and 86.5% respectively when the volume fraction of steel fiber increases from 0 % to 1%, 2 % and 3 %. The linear relationship of autogenous shrinkage in 33 h with both water-binder ratio（below 0.24） and the volume fraction of steel fiber（from 0% to 3 %） is clearly found.