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通过不同厚度超高韧性水泥基复合材料(UHTCC)试件的四点弯曲试验,研究了厚度对其弯曲性能的影响,并通过理论量纲分析做了进一步解释。结合ASTM C 1609标准,提出了以单位塑性铰区体积的能量消耗Tv为参数的韧性评价方法。试验结果表明:不同厚度试件的名义弯曲应力-弯曲应变曲线与裂缝宽度变化曲线几乎重合;挠度随厚度增大呈反比例下降;在极限破坏时,中和轴高度与试件厚度比约为0.88。对于ASTM C 1609标准,韧性指数随厚度的增大而增大,而新提出的韧性指数Tv与试件厚度无关。对于拉应变硬化的超高韧性水泥基复合材料,弯曲强度、韧性性能和裂缝宽度均不存在尺寸效应。建议选用与普通FRC材料韧性及弯曲性能测定相同的试件尺寸(100 mm×100 mm×400 mm)作为标准试件形式。
Through the four-point bending test of UHTCC specimens with different thicknesses, the influence of thickness on the bending properties was studied and further explained by theoretical dimension analysis. Combined with ASTM C 1609 standard, the method of evaluating toughness based on the energy consumption Tv of the unit plastic hinge zone volume is proposed. The experimental results show that the nominal bending stress-bending strain curves of the specimens with different thicknesses almost coincide with the variation curves of the crack width, the deflection decreases inversely with the increase of the thickness, and the ratio of the neutral axis height to the specimen thickness is about 0.88 . For the ASTM C 1609 standard, the toughness index increases with increasing thickness, whereas the newly proposed toughness index, Tv, is independent of the thickness of the test piece. For tensile strain hardening ultra-high toughness cement-based composites, there is no size effect on flexural strength, toughness and crack width. It is recommended to select the same specimen size (100 mm × 100 mm × 400 mm) as that of the ordinary FRC material for determining the flexural and flexural properties as the standard specimen form.