A STUDY ON BONDING STRENGTH OF POLYMERIC FIBERS TO CEMENTITIOUS MATRIX

Cementitious materials are brittle in nature. Due to this behavior, short, randomly and distributed fibers are mostly being used to reinforce cementitious materials. Added fibers enhance tensile strength and flexural toughness and reduce crack creation and propagation in cement matrix. The major effect of fibers is to act as bridging at crack tips to resist crack propagation. Fiber bonding to cement paste is an important factor that affects performance of the fiber reinforced cementitious composite (FRCC). Bonding energy (adhesion) between these materials is composed of interfacial interactions (chemical bonding) and mechanical interactions (interlocking). The adhesion of fiber to cementitious materials can be evaluated by pull-out test. This test is the newest method and one of the most commonly used practical methods to evaluate performance of fibers in FRCCs. This article presents the bonding strength results of commercial polymeric fibers to cement matrix. To investigate adhesion of polypropylene (PP), nylon66 (N66) and acrylic (PAN) fibers to cement matrix a single fiber pull-out test setup is designed and fabricated. The specimens were prepared at the water-cement ratio of 0.4 and they were tested at 7, 14 and 28 days of curing. Fiber's surface after pull-out test was also studied by microscopic analysis. Some interesting results were obtained from the pull-out test of different fibers. On the basis of results, it was found that fiber should be selected for FRCC reinforcement due to their mechanical interactions and physical/chemical/mechanical behavior in cement matrix instead of their chemical interactions.

Keywords:

adhesion , pull-out test , interfacial interactions , polymeric fibers