C40自密实混凝土II型断裂韧度的确定

Determination of Type II Fracture Toughness of C40 Self-Compacting Concrete

自密实混凝土的II型断裂韧度是个很重要的材料参数,而对其II型断裂的研究,有助于我们建立复杂裂缝扩展准则并且探索构件断裂失效.为了解自密实混凝土II型断裂破坏过程并确定其II型断裂韧度,本文制备了7组21个不同缝高比以及不同切口方式的试件,利用半对称加载方式对自密实混凝土做了II型断裂实验,并利用ABAQUS有限元建模,模拟计算了各个试件的II型断裂韧度.实验结果表明,自密实混凝土比普通混凝土粒径小,断裂脆性大,多是沿韧带剪切破坏,自由端剪切崩落.实验与模拟计算的II型断裂韧度一致,其大小为1.95MPa√m.由于骨料粒径小,K_(Ⅱc)的值比普通混凝土稍低一些,并且其值与材料强度呈正相关,与试件宽度呈负相关,半边对称加载的实验方式可以准确反映自密实混凝土的II型断裂韧度.单边切口与双边切口试件断裂韧度值相差不大,切口方式对K;影响很小,且初始缝高比对断裂韧度无影响.

The type II fracture toughness of self-compacting concrete is a very important material parameter.Study of its type II fracture can help us establish complex crack propagation criteria and explore the failure of components.In order to understand the type II fracture failure process of self-compacting concrete and to determine its type II fracture toughness,this paper prepared 7groups of 21 specimens with different joint height ratios and different notch modes.The type II fracture tests of semi-symmetrical loading style was perform on the self-compacting concrete.Combined with the finite element simulations using ABAQUS,the type II fracture toughness of each specimen were calculated.The test results show that self-compacting concrete has a smaller particle size and greater fracture brittleness than the ordinary concrete,with the shear failure mostly occurred along the ligament,and the shear collapse occurred at the free ends.The type II fracture toughnesses calculated by the experiment and the simulation are consistent with each other,with the value of 1.95MPa√m.Because the aggregate particle size is small,its type II fracture toughness is slightly lower than that of ordinary concrete,and is positively correlated to the strength of the material,and negatively correlated to the width of the specimen.The experiments of semi-symmetrical loading can accurately reflect the type II fracture toughness of self-compacting concrete.The fracture toughness values of the specimens with single-edge notch and double-edge notch are not much different,the notch mode has little effect,and the initial slit height ratio has no effect on the fracture toughness.