The direct shear behavior of recycled lump concrete

作者：Li, Zhen; Wu, Bo^*

来源：MATERIALS AND STRUCTURES, 2021, 54(6): 226.

DOI：10.1617/s11527-021-01823-6

• Recycled concrete lumps
• Recycled lump concrete
• High-strength concrete
• Direct shear strength
• Compressive strength
• Size effects

To study the direct shear behavior of recycled lump concrete, 116 prismatic specimens were fabricated and tested under double-direct shear loading. Four variables were considered: the replacement ratio of recycled concrete lumps, the characteristic ratio of recycled concrete lumps (i.e., the characteristic size of lumps as divided by the lateral dimension of prism), the prisms' lateral dimension and the strength of fresh concrete matrix. A formula has been established, which adequately predicts the direct shear strength of the recycled lump concrete. Moreover, a model presented describes the relationship between the size of the prism tested and the direct shear strength observed. The direct shear strengths of fresh concrete and recycled lump concrete present a smaller gap than the compressive strengths of them. With normal-strength concrete as the matrix, the ratio of the direct shear strength to the compressive strength for recycled lump concrete is about 0.91 times that for fresh concrete alone. With high-strength concrete as the matrix, the ratio is about 1.08 times. For a given size of specimen, the impact of lump size on the direct shear strength of the recycled lump concrete is basically negligible. At a given characteristic ratio of lumps, the size of specimen impacts on the direct shear strength of recycled lump concrete in a similar way to the direct shear strength of conventional concrete.