试样尺寸对超高性能混凝土断裂性能影响的试验研究

摘要

采用3种不同尺寸的预制缺口试样进行三点弯曲试验,研究试样尺寸对超高性能混凝土(UHPC)断裂性能的影响,利用数字图像相关法(DIC)观测裂纹张开宽度(CMOD),并分析荷载-裂纹张开宽度的关系.结果表明,拉伸试验中钢纤维体积掺量为2%时,UHPC呈现较好的应变硬化特性.随着试样尺寸的增大,比例极限(LOP)和断裂模数(MOR)均有所下降,其中LOP下降较为平缓,而MOR对试样尺寸大小更加敏感,下降幅度较大.这是因为对于同种配合比的UHPC,其LOP的主要影响因素是基体的初裂性能,而MOR主要取决于试样中钢纤维的分布,由试样尺寸大小引起的钢纤维分布取向差异.%The effects of specimen size on fracture properties of ultra high performance concrect(UHPC)were studied by three-point bending test with three kinds of prefabricated notch specimens in different size. The crack mouth opening displace-ment(CMOD)was observed and the relationship between load and CMOD was analyzad by digital image correlation method(DIC). The results showed that UHPC exhibited good strain hardening when the fiber volume was 2% in the tensile test. The limit of proportionality(LOP)and the modulus of fracture(MOR)decreased with the increase of the specimens size,but the LOP decreased more slowly while the fracture modulus was quite sensitive to the size of the specimen,showing a sharp downward trend. This was because that in same component UHPC,the LOP was influenced a lot by initial cracking properties of matrix while the MOR de-pends mainly on the distribution of the fibers which caused by the different size of specimens.