Cracking processes in steel fiber reinforced cement paste: Fid-Bau Portal

Cracking processes in steel fiber reinforced cement paste

Bentur, Arnon / Diamond, Sidney / Mindess, Sidney

AbstractFracture patterns produced when a crack advanced from a notch in cement paste specimens reinforced with steel fibers were studied by SEM methods. The specimens were small compact tension specimens with precast notches that could be wedge loaded within the SEM chamber in a moist environment. Steel fibers were positioned either in an array of five parallel fibers spaced 2 mm apart and across the expected crack propagation path, or else were in random orientation on the plane being observed. The cracks induced by wedge loading were found to be geometrically complex and certainly could not be described as simple straight cracks as assumed in various models. On intersection with fibers oriented perpendicularly to them, the cracks tended to displace laterally and branch into a number of microcracks; on intersection with fibers at less than perpendicular angles, the tendency was for the crack to change course and run parallel to the inclined fiber. Often at perpendicular intersections the crack appeared to be arrested in the matrix 10 to 40 μm ahead of the actual fiber interface, and then produced a “pseudo-debonding crack” parallel to the fiber but some distance away from the actual interface. These cracking patterns are considered to be influenced by the microstructure of the cement paste near the interface, which is clearly different from that of the bulk cement paste.