Effect of Curing Conditions on the Interfacial Bonding Parameters of High-Tenacity Polypropylene (HTPP) Fiber / Cementitious Matrix

Engineered cementitious composites (ECC) provide enhanced ductile behavior thanks to multiple-cracking arising from the synergistic optimization of fiber-matrix interface adhesion behavior. According to the micromechanics based design theory of ECC, there are two critical conditions that should be satisfied to guarantee the strain-hardening. According to the first condition fiber bridging strength should be greater than the cracking strength for any crack plane. Secondly, complementary energy of fiber bridging should be greater than the crack tip toughness. Both criteria are directly related with the fiber/matrix interface bonding parameters and critical for the success of ECC design. These interfacial bonding parameters are well documented for poly-vinyl alcohol (PVA) fiber reinforced ECC and poly-ethylene (PE) fiber reinforced ECC. However, interfacial bonding parameters need to be determined for the relatively new type of ECC known as high-tenacity polypropylene fiber reinforced ECC (HTPP-ECC). This study focuses on the effect of different curing conditions on HTPP fiber/matrix bonding parameters (frictional bond strength, slip hardening coefficient and chemical debond-related energy). These parameters have been experimentally determined by using a special single fiber pull-out test setup. Results showed that water curing or partial water curing at the initial periods of hydration has a positive influence on fiber/matrix frictional bond strength. The chemical debond-related energy and slip hardening coefficient values of HTPP-ECC interfaces were found excessively low and did not significantly affected from the curing conditions, which is reasonable for most of the hydrophobic fibers.

کلیدواژه ها:

Fiber reinforcement ، Engineered cementitious composites ، single fiber test ، Curing ، interfacial bond strength