The fragmentation of standard concrete cylinders under compression: the role of secondary fracture debris

Abstract

The paper presents an alternative view on the standard concrete cylinder compressive test. Basically, the problem is discussed in terms of a single-grain comminution process. Five different mixtures are investigated. After compressive testing, the primary fracture debris as well as the samples of secondary fracture debris are collected and analysed. Due to sieve analysis, the grain-size distribution of the secondary debris is estimated. Furthermore, the debris shape is evaluated. It is found that the secondary debris are distributed according to a Rosin–Rammler–Sperling distribution. The distribution parameters depend on concrete stiffness and strength. The shape factor increases as stiffness and strength increases. Generally, with an increase in stiffness and strength, the fracture becomes irregular. This aspect is discussed by assuming some type of ‘homogenisation’ for the fracture process due to sudden release of strain energy during the post-peak failure. Calculations of the specific crack surface area and the specific crack energy, based on the grain-size distribution parameters, show that the ‘homogenisation’ increases the specific crack energy. The specific crack surface area is almost independent of the material. The methodology developed in the paper can be used to alternatively discuss phenomenological features of the standard cylinder compressive test.