PSI - Issue 5

A.A. Abd-Elhady et al. / Procedia Structural Integrity 5 (2017) 19–26 Mubaraki et al./ Structural Integrity Procedia 00 (2017) 000 – 000

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It is found that the crack path at different modes of mixity is independent of the mechanical properties of the materials, i.e., it is not affected by changes in the value of W/C ratio or RAP%. This finding is in agreement with the conclusions drawn by Sallam and Abd-Elhady (2012).

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(a-1) SCB-1 & Pure Mode I

(a-2) SCB-1 & Mixed Mode I/II

(a-3) SCB-1 & Pure Mode II

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(b-1) SCB-2 & Pure Mode I

(b-2) SCB-2 & Mixed Mode I/II qq

(b-3) SCB-2 & Pure Mode II

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(c-1) SCB-3-1 & Pure Mode I

(c-2) SCB-3-1 & Mixed Mode I/II

(c-3) SCB-3-1 & Pure Mode II

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(d-1) SCB-3-2 & Pure Mode I

(d-2) SCB-3-2 & Mixed Mode I/II

(d-3) SCB-3-2 & Pure Mode II

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Fig. 2. Progressive crack growth with SCB-1, SCB-2 and SCB-3 specimens, using XFEM

3.2 The effect of the mode of mixity on the load-displacement relationship

Figure 3 illustrates the effect of mode of mixity and SCB specimen geometry on the load-displacement diagram for concrete pavement with W/C ratio = 0.43 and RAP% =0. Firstly, the initial stiffness is not affected by the mode of mixity for either of the specimen geometries. By increasing the applied load, the effect of mode mixity on stiffness became clear. Where the pure mode II has the highest stiffness, pure mode I has the lowest stiffness for both specimen geometries. When the load reached about half of its maximum value, the linear relationship between the load and displacement converted to become nonlinear, i.e., it entered the crack initiation zone. When the load reached its maximum load, i.e. unstable crack growth (the commencement of the descending part), the applied load decreased gradually with increasing displacement. It is worth noting that the descending part of the curve can be obtained if the specimen is tested under displacement control. As is already known, for the same pre-cracked position, i.e., pure mode I in specimens SCB-1 and SCB-2, the maximum load increases by decreasing the span (2S), see Fig. 3 and Table 2. The resistance of the material to fracturing increases by increasing the value of mode of mixity; hence, the maximum load increases by increasing the mode of mixity.