含砖粒再生粗骨料取代率对混凝土断裂性能的影响

Effect of Replacement Rate of Brick-containing Recycled Coarse Aggregates on Fracture Concrete Performance

为了探究含砖粒再生粗骨料取代天然石料对再生混凝土断裂性能的影响,制作4组不同取代率的再生混凝土梁试件,通过三点弯曲梁试验,研究各组再生混凝土的双K断裂参数、断裂能及延性指数;通过数字图像处理,对试件断面水平投影方向上的粗骨料分布进行量化,并应用差分盒算法提取试件断面分形维数用于表征其粗糙度。结果表明:再生混凝土的各项断裂参数均随含砖粒再生粗骨料取代率的增大而逐渐降低,起裂韧度较失稳韧度更容易受含砖粒再生粗骨料掺入的影响;含砖粒再生粗骨料水平投影面积与混合粗骨料水平投影面积之比可以在一定程度上反映其取代水平;随着取代率增大,试件断面分形维数逐渐降低,且断面分形维数与断裂能有较好的相关性,得出考虑含砖粒再生粗骨料取代率的断裂能与分形维数的回归方程。

In order to investigate the effect of brick-containing recycled coarse aggregate instead of natural stone on the fracture performance of recycled concrete,four sets of recycled concrete beam specimens with different substitution rates were fabricated.Through the three-point bending beam test,data of all sets of the double-K fracture parameters,fracture energy and ductility index of each group of recycled concrete was studied.Then,the digital image processing was used to quantify the coarse aggregate distribution in the horizontal projection direction of the specimen section,and the differential box algorithm was used to extract the fractal dimension of the specimen section to characterize its roughness.The results show that each fracture parameters of recycled concrete decrease with the increase of the replacement rate of coarse aggregates containing bricks.The initial fracture toughness is more susceptible to the inclusion of coarse aggregates containing bricks than unstable toughness.To some extent,the ratio of the horizontal projected area of the coarse aggregate containing brick to the horizontal projected area of the mixed coarse aggregate can reflect the level of substitution.As the replacement rate increases,the fractal dimension of the specimen section gradually decreases,and the fractal dimension is well correlated to the fracture energy value.It is concluded that the regression equation of fracture energy and fractal dimension considering the replacement rate of coarse aggregates containing bricks.