Crack Stability in the Fracture of Cementitious Materials

Abstract

The aim of the present study is to investigate the stability of crack propagation in cementitious materials. Tests were conducted on bend specimens in three-point and four-point loading conditions.Three-point bend specimens showed stable crack growth for mortar, normal strength and high strength concrete specimens. Alternatively, four-point bend specimens showed catastrophic failure for mortar and quasi-catastrophic failure for normal strength and high strength concrete specimens. Results will be discussed in relation to brittleness number model and specific microstructural features including the interfacial transition zone between the cement paste and the aggregate and the attendant toughening mechanisms.

Design of four-point SENB specimens with stable crack growth

“…show similar trend as those curves reported in the literature [15,33]. All curves, except of the first ∼ 0.05 mm, starts with a linear part until the onset of crack propagation where the moment drops.…”

“…for measuring fracture toughness, but also for other purposes with varying geometry, material and setup [23,24,25,26,27,28,29,22,30,12,31,32]. Four-point SENB specimen geometries, found in the literature [15,28,33,20,30,12], vary significant from test to test: were tested experimentally by Tandon et al [33] for three different material systems using homogenous four-point SENB specimens. One of the conclusions was that a smaller h improved the stability of the four-point SENB test since the amount of elastic energy in the beam was reduced [33].…”

Acoustic Emission and Modal Frequency Variation in Concrete Specimens under Four-Point Bending

“…Here, they were tested in a four-point bending configuration instead of a three-point one. The former configuration, compared to the three-point bending scheme, may result in a more brittle behavior of the specimen, with unstable crack growth [28]. However, the four-point configuration is more suitable for the dynamic testing of a specimen notched at midlength; in fact, this avoids having a support-and therefore a fixed node in the modal shapes-in correspondence to the weakened section.…”

Identification of microscale fracture models for mortar with in-situ tests

“…Failure was brittle, followed by substantial force drop, and very fast crack propagation on the major part of the ligament (Figure 3). It can be noted that the crack stability in three-point flexure depends on the sample geometry and notch depth, as well as the stiffness of the testing setup [72]. Therefore, control of fracture propagation may be improved in further studies by modifying the beam dimensions.…”