水泥净浆和水泥砂浆材料的Ⅰ型断裂韧度测定

Determination of mode I fracture toughness of cement paste and mortar

本文针对水泥净浆和水泥砂浆两种灌浆材料,采用三点弯曲梁进行了不同强度、不同尺寸以及不同初始缝高比的断裂试验。根据水工混凝土断裂试验规程,利用试验中测得的最大荷载及对应的裂缝口张开位移计算了水泥净浆和水泥砂浆的失稳断裂韧度,并通过电阻应变片法确定的起裂荷载得到了二者起裂韧度的实测值。试验中发现,水泥净浆并不是一经起裂就失稳破坏,而是在失稳破坏前存在着一个比较明显的裂缝稳定扩展过程。结果表明,随试件强度的提高,两种材料的起裂韧度和失稳韧度均增大,而随试件尺寸和初始缝高比的变化,水泥净浆的起裂韧度和失稳断裂韧度都大致为常数,表现为尺寸无关性,但对水泥砂浆,起裂韧度随试件尺寸的增大而减小而失稳断裂韧度基本保持不变。

The three-point bending beam fracture test for cement paste and mortar specimens with different strengths,dimensions and initial crack-depth ratios was carried out.According to the measured maximum load Pmax and the corresponding crack mouth opening displacement CMODc the unstable fracture toughness KIc^un of cement paste and mortar were evaluated.The initial fracture toughness KIc^ini was measured by electric resistance strain gauge technique.The observation shows that apparent stable crack propagation occurred prior to the unstable failure.The test results show that the KIc^ini and KIc^un of cement paste and mortar increase with the increase of compression strength.The KIc^ini of cement paste keeps constant with the change of beam depth and initial crack-depth ratio and is independent of size.While for mortar,with the increase in beam depth the KIc^un does not change,but the KIc^ini decreases.