Effect of Crack Control in Mortars Containing Polypropylene Fibers on the Corrosion of Steel in a Cementitious Matrix

Abstract

Low-volume polypropylene fiber reinforcement is known to be effective in reducing plastic shrinkage cracking. In the present work this advantage of fiber reinforcement is evaluated in terms of its influence on the corrosion of steel in concrete, which is sensitive to the presence of cracks in the matrix. Mortar specimens with reinforcing bars were exposed to restrained shrinkage conditions by drying immediately after casting. Some of the matrixes were reinforced with low-volume polypropylene fibers. After the initial curing the specimens were held in corrosive conditions in contact with chloride solutions and the corrosion rate of the bars was monitored by electrochemical means and the visual observations of crack developments. No clear correlation was established between cracking induced at early age and corrosion rate when each bar was analyzed individually within each specimen. However, when the general trends between the various specimens tested were addressed it could be concluded that for systems of the same matrix composition, the ones with fibers seemed to crack less initially and later had somewhat lower corrosion rates as measured by the linear polarization method. In addition, the fiber reinforced specimens demonstrated an ability for self-healing of cracks under corrosive environments, whereas the plain mortar specimens under the same conditions showed a tendency for increase in the width of the cracks formed at early age.