粗聚烯烃纤维混凝土圆板弯曲韧性和表征方法

通过圆板试件研究了新型粗聚烯烃纤维混凝土的弯曲韧性,探讨了纤维掺量、纤维长度和基体强度等对圆板能量吸收值的影响规律.试验发现:纤维掺量与圆板能量吸收值成正比;纤维长度介于38~60mm时,圆板能量吸收值随纤维长度增加而增大,当纤维长度≥48mm时,其荷载-挠度曲线下降段出现应变强化特征,荷载有2次峰值.分析了美国ASTM C1550在评价韧性方面存在的问题,提出了以圆板初裂挠度为初始参考挠度,基于能量比值法的韧性指标评定方法,该方法可表征粗纤维对混凝土板初裂后韧性的贡献,并可直接与理想弹塑性材料的韧性指标进行比较.

Flexural Toughness and Its Characterization of a New Kind of Macro polyolefin Fiber Reinforced Concrete Plate

In order to examine the toughness of concrete circular plates reinforced with a new type of macro polyolefin fiber, a circular plate test was performed and the effects of fiber use level, fiber length and the matrix strength on the flexural toughness, energy absorption value were investigated. The test results show that the absorption energy value is proportional to fiber use level; when fiber length is between 38 to 60mm, the absorption energy value increases with increasing fiber length. When the fiber length is greater than or equal to 48mm, in the descending stages on the load deflection curve strain hardening behavior appears with two peak loads. The problems with evaluating the flexural toughness using ASTM C1550 were analyzed based on the energy ratio method, and a new toughness evaluating method was proposed. This new method, taking the first crack deflection as the initial reference deflection, can be used to characterize the contribution of macro polyolefin fiber to the flexural toughness after initial crack, and can directly used to compare the toughness index with perfect elastoplastic material.