Pure mode I and mode II fracture toughness of asphalt mixture was investigated both experimentally and theoretically using vertical edge crack semicircular bend (SCB) specimen with symmetric and asymmetric bottom loading spans. The thickness of SCB specimen was considered in the range from 30 to 70 mm, and the fracture toughness tests were performed at three subzero temperatures (−5°C, −15°C and −25°C). The results showed that K_Ic and K_IIc are increased by reducing the test temperature. The thickness had no sound effect on the fracture toughness, but the thickness of 50 mm was more suitable for fracture study on this material. The fracture load of mode II specimen was significantly greater than the mode I fracture load at the same testing condition. The fracture toughness ratio (K_IIc/K_Ic) that varies in the range between 1 and 1.4 was predicted theoretically using three well‐known stress/strain‐based fracture criteria.

中文翻译：

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低温下热拌沥青混合料的KIc和KIIc测量：使用不同厚度的半圆形弯曲试样的实验和理论研究

使用具有对称和不对称底部载荷跨度的垂直边缘裂纹半圆弯曲（SCB）标本，通过实验和理论研究了沥青混合料的纯I和II型断裂韧性。SCB试样的厚度被认为在30至70 mm的范围内，并且在三个零下温度（-5°C，-15°C和-25°C）下进行了断裂韧性测试。结果表明，K _Ic和K _IIc通过降低测试温度来增加。厚度对断裂韧性没有影响，但是50mm的厚度更适合于这种材料的断裂研究。在相同测试条件下，II型试样的断裂载荷明显大于I型试样的断裂载荷。理论上，使用三种众所周知的基于应力/应变的断裂准则预测了断裂韧度比（K _IIc / K _Ic）在1至1.4之间变化。