Importance of the surface roughness of a steel fibre pulled out from cement paste by slowly increasing load cycles

Pull-out tests of fibres were conducted using slow cyclic tension to evaluate the behaviour of the bond between cement paste and steel fibres with different types of surface roughness. Even though the load amplitude increases in small steps between the cycles, the development of the residual slip increment proves the absence of a complete bond at the beginning of loading. During the load steps, the residual slip evolves in the deceleration, steady, and acceleration stages. The bond stiffness during the ascending and descending parts of the load-slip curve increases up to the last load cycles, indicating that loading compacts the matrix near the fibre surface. The growth of the roughness of the fibre surface increases the amount of cement paste adhered to the surface of fibres pulled out, explaining the changes in the behaviour of the bond and the increase in the pull-out capacity of these fibres.

Automated summary

Pull-out tests were conducted to evaluate the bond behavior between cement paste and steel fibers with different surface roughness. The bond stiffness increased with increasing load in the ascending and descending parts of the load-slip curve.