Cement paste crack propagation

Zhang, M.H. (1995) Microstructure, crack propagation and mechanical properties of cement pastes containing high volumes of fly ashes. Cement and Concrete Research... 

Figure 7.9 Scheme of steel fibre-cement paste interface with a crack propagating in transversal direction, after Bentur et aL (1985). 

Opening and propagation of cracks in cement pastes, mortars and concretes may be detected and followed by analyzing acoustic signals that accompany these events. The number and energy of the signals is recorded and analyzed. The acoustic emission events are produced by cracking and also the nature... 

For highly brittle materials like glass or cement paste R characterizes the material and any crack propagation from the initial notch or flaw leads to a rapid failure of the element. The sitnation is different in materials with an internal structure, which stops and may control the crack propagation, that is, in materials like mortar, concrete and fibre-reinforced concrete. The crack is propagating slowly until reaching the second condition ... 

A system of microcracks appears during the initial period of hardening of the cement paste. It is later subjected to the action of external loads and imposed deformations, which vary over time. Local stress concentrations contribute considerably to crack propagation also under relatively low to average stresses. In certain conditions, the microcracks may exhibit healing (cf. Section 9.7). In most cases, however, they remain and may develop into major cracks leading to disintegration of elements. 

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