Study of the failure properties and tensile strength of rock-mortar interface transition zone using bi-material Brazilian discs. (10th March 2020)

• Record Type: Journal Article
• Authors: Qiu, Hao; Zhu, Zheming; Wang, Meng; Wang, Fei; Luo, Caisong; Wan, Duanying
• Is Part Of: Construction & building materials. Volume 236(2020)
• Publication Date: 2020-03-10
• Subjects: Bi-material -- Brazilian disc -- Interface roughness -- Tensile strength -- Static load -- Impact load -- Interface transition zone; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2019.117551
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: In the static tests, a 300 kN computer controlled electronic universal testing machine was applied, and in the dynamic tests, a split Hopkinson pressure bar (SHPB) system with 80 mm in bar diameter was employed. To investigate the effect of rock interface roughness on the ITZ tensile strength, the rock interface were proceed into two different roughness, i.e. rough and smooth interface for the BBD specimens. Numerical models embedded with cohesion elements were established by ABAQUS code using the Python language. For bi-material Brazilian discs (BBDs), an experimental-numerical method is proposed to calculate the critical stress of the BBD under critical loading condition, and this critical stress is considered as tensile strength. Abstract: The interface transition zone (ITZ) between aggregate and mortar of concrete has a weak resistance to static or dynamic loading and failure usually starts from this zone. Therefore, it is essential to study the failure properties and tensile strength of ITZ of concrete under static and dynamic loading. Accordingly in this paper, bi-material specimens of rock-mortar Brazilian Disc were designed. Two types of rock granite and sandstone with smooth and rough surface were selected to prepare the bi-material Brazilian disc (BBD) specimens. Meanwhile, to compare the difference of failure properties with single material, the Brazilian disc (BD) specimen of single granite, sandstone and mortar were also prepared. The static and impact tests were conducted using the BBD and BD specimens, and a split Hopkinson pressure bar (SHPB) device was applied in the impact tests. Because of asymmetry stress distribution in the bi-material Brazilian disk, the tensile strength was determined by an experimental-numerical method. In addition, to simulate the failure process in ITZ, numerical models of the BD and BBD specimens embedded with cohesive elements using Python language were established. The results show that under static loading, the tensile strength of bi-material sandstone-mortar is less than that of both the single sandstone and mortar, while the tensile strength of granite-mortar is slightly lower than that of the mortar but much less than that of the granite. The tensile strength of bi-material with rough rock surface is generally higher than that with smooth rock surface. The dynamic tensile strength is more than 20 times the corresponding static tensile strength, and the dynamic tensile strength increases with loading rates.