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Concrete deterioration mechanisms (A)
Published in Brian Cherry, Green Warren, Corrosion and Protection of Reinforced Concrete, 2021
Crazing occurs whenever a weak surface layer is formed on the surface and this weak surface layer is unable to withstand quite small stresses which result from the differential shrinkage between the surface and the bulk. This may arise as a result of the separation of aggregate and cement in the very early stages of curing which leaves a thin layer of ‘laitance’ on the surface of the concrete or it may result from the very rapid evaporation of water from the surface of the concrete when it is placed under hot conditions. Crazing is shown at J and K in Figure 2.3.
The structure and properties of crazed polymers
Published in A. L. Volynskii, N. F. Bakeev, Surface Phenomena in the Structural and Mechanical Behaviour of Solid Polymers, 2018
As already mentioned, crazing is a special type of the inelastic, plastic deformation of the polymer which is accompanied by the rapid development of its interfacial surface. Many aspects of this phenomenon are still unclear but undoubtedly the following is obvious: the polymer as a result of crazing acquires a high level of the interfacial surface. Below, the attempt to characterise the purposes of the crazed polymers from this viewpoint.
Sierraclad™ Bird-Proof Canopies And Windshields
Published in Ralph D. Hermansen, Polymeric Thermosetting Compounds, 2017
For those unfamiliar with the term “crazing,” it is a phenomenon which occurs in polymers, where narrow microscopic gaps develop in the material. Crazes are only visible because light reflects off the surfaces of the gaps. A craze is different from a crack because it cannot be felt at the surface and the plastic can still support a load. Crazes form at stressed areas and tend to propagate perpendicular to the applied tension. Polymers such as polystyrene, acrylics, and polycarbonate are especially prone to crazing.
Links between surface morphology changes and damage in a toughened epoxy adhesive
Published in The Journal of Adhesion, 2022
Toughened polymeric materials can contain initial defects (e.g., cracks, surface non-uniformities, etc.), which serve as initiation points for the development of damage mechanisms such as crazing, particle cavitation and shear banding. Crazing can be described as the development of fibrils/tendons that delay crack opening and allow the material to absorb more deformation energy prior to ultimate failure. Although crazing is a significant failure mechanism in toughened thermoplastics, [9] it is a controversial topic in epoxy materials. While certain authors acknowledge the possibility as presented by Yee and Pearson[36]; others as presented by Garg[31] dispute the presence of this mechanism. To further complicate the subject, craze-like damage in toughened epoxies has been reported in the literature .[37,38]