Creep and residual properties of cracked macro-synthetic fibre reinforced concretes

SERNA ROS, P.; MARTI VARGAS, R.; BOSSIO, M.E.; ZERBINO, R.

MAGAZINE OF CONCRETE RESEARCH

THOMAS TELFORD PUBLISHING

Año: 2016 vol. 68 p. 197 - 207

0024-9831

Fiber reinforced concrete (FRC) is a high performancematerial where the fibers control the propagation of cracks improving thetoughness and durability of the structures. Fibers are frequently incorporatedin concrete to improve the service life of the structures in many applications.However, there are only few studies on the behavior in the cracked state. The analysisof this behavior becomes relevant given the great variety of types of macro-syntheticfibers (MSF). In this study, the creep behavior of five FRC incorporating four differenttypes of MSF and one type of steel fiber is analyzed. Each FRC included a singletype of fiber with a fiber content of 0.5% in volume of concrete. Prismatic specimensof 150x150x600 mm were cast and cured during 28 days in a moist room undercontrolled conditions. Then, specimens were pre-loaded up to a crack opening of0.5 mm and were classified in three groups. During 90 days, the first groupremained in laboratory conditions, the second group was immersed in sea waterat 45°C and the third group was exposed to air flow at 45°C. After this period,three specimens of each group were submitted to long term loads during 90 dayswhile other three specimens of each group remained unloaded. Finally, bendingtests up to a crack opening of 4 mm were performed on all specimens inorder to evaluate the remaining residual capacity. It is concluded that theremaining residual capacity of cracked MSF concretes, even those exposed in seawater, is not significantly affected by long term loading. Creep strains were alwaysgreater in concretes reinforced with MSF than in the case of steel fibers. Inall tested cases the crack opening rate significantly decreased after the first two weeks under loading and no risks of failure were detected in any case.