粗骨料体积含量对混凝土断裂参数的影响

EFFECT OF COARSE AGGREGATE CONTENT ON FRACTURE PARAMETERS OF CONCRETE

该文采用尺寸为100mm×100mm×400mm预切口梁的三点弯曲试验得到P-CMOD曲线,采用基于粘性裂纹模型的逆分析方法导出混凝土的抗拉软化关系(σ-w曲线),借此重点研究了粗骨料体积含量对3个系列水胶比(0.62、0.43、0.3)混凝土力学性质和断裂参数的影响。保持混凝土水胶比以及砂浆组成不变,仅增加配合比中粗骨料含量,三种水胶比混凝土的抗压强度、抗弯强度、开裂强度、抗拉强度均随之增大,中高水胶比(0.43、0.62)混凝土的断裂能则随之增大,低水胶比(0.3)混凝土的断裂能先增大后减小。增加粗骨料体积含量,高水胶比(0.62)混凝土的特征长度逐渐增大,延性变好;中低水胶比(0.43,0.3)混凝土的特征长度变化则很小,基本保持常数;但低水胶比(0.3)混凝土的特征长度明显小于中高水胶比(0.62,0.43)混凝土的值,脆性特征突出。

The influence of aggregate content on mechanical properties and fracture parameters of concrete of three different water-to-binder ratios of 0.62, 0.43, 0.3 was investigated in present research. Three-point bending tests of notched beam specimens with size of 100mm× 100mm×400mm were carried out, and the tension-softening relationships （σ-w curve） of concrete were derived from the Load-CMOD curves using an inverse analysis, fracture parameters of concrete were obtained. The results show that keeping water-to-binder ratio and mortar composition to be unchangeable, leads the compressive strength, flexural strength, increasing coarse aggregate content in the mixture proportion cracking strength and tensile strength of the three series of concrete to increase. As coarse aggregate content increases, fracture energy increases for the concrete with higher water-to-binder ratios of 0.62, 0.43. By contrast, it first increases then decreases for the concrete with a low water-to-binder ratio of 0.3. With the increase of coarse aggregate, the characteristic length increases for the concrete with a high water-to-binder ratio of 0.62, indicating a better ductile property, which can also be observed in Load-CMOD curves and σ--w curves, whereas it nearly keeps as a constant for the concrete of lower water-to-binder ratios of 0.43, 0.3. Furthermore, the characteristic length of concrete of a low water-to-binder ratio of 0.3 is much smaller than that of concrete of higher water-to-binder ratios of 0.62, 0.43, implying it is more brittle.