The direct shear behavior of recycled lump concrete

Abstract

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.

Mixture ratio optimization of basalt fiber recycled aggregate concrete based on RSM

“…At present, most of the scholars refer to the ordinary concrete proportion design specification for recycled aggregate concrete proportion design, and use orthogonal test to seek the optimal proportion [10][11][12]. However, when using orthogonal tests to seek the optimal proportion, the consideration of the interaction between factors will lead to a large amount of workload, and it is not possible to obtain a clear functional relationship between the factors and the response values in the specified area [13,14].…”

Experimental study on mechanical properties of recycled aggregate concrete with polypropylene fiber under combined compression‐shear loading

“…However, concrete in practical engineering, such as corbels, highways, bearing padding stones, and deep beams, is usually subjected to combined compression-shear loads during service. [37][38][39][40] Then the study of RAC under complex stress state is very important. Deng et al 41 and Wang et al 42 performed the direct shear tests and the compressionshear tests on RAC and revealed a significant difference in the shear behavior between RAC under pure shear stress and combined compression-shear stresses.…”

“…More importantly, some researchers found that the drops in splitting tensile strength and flexural strength due to the substitution of NCA with RCA were to a large extent compensated by the addition of PP fibers. However, concrete in practical engineering, such as corbels, highways, bearing padding stones, and deep beams, is usually subjected to combined compression‐shear loads during service 37–40 . Then the study of RAC under complex stress state is very important.…”