Abstract
The historical data showed a positive influence of polypropylene fibers (PPF) on concrete performance in terms of mechanical properties, shrinkage and fire resistance. However, in regards to fresh state properties, the workability is negatively affected by fibers inclusion. Therefore, several studies have been done to evaluate the workability loss of fiber-reinforced concrete (FRC), but there has been little research about the rheological and tribological properties such as the plastic viscosity and the viscous constant. In this context, the present study aims to evaluate the effect of PPF inclusion on both rheological and tribological properties of ordinary concrete through two phases (without and with incorporation of superplasticizer), using fibrillated twist and wave fibers shapes at different dosages (0.12, 0.24, 0.36%) and with various lengths (19, 30 and 54 mm). The obtained results of the first part showed that the plastic viscosity of FRC without superplasticizer is not affected by fibers length while it augments with increasing PPF percentage. Regarding the tribological behavior, segregation phenomenon was observed for mixtures with high fiber dosage (0.24 and 0.36%) during the test. In the second part, the use of superplasticizer has improved the concrete workability in addition to the rheological and tribological behaviors. Finally, a special attention was devoted to the effect of using two different shapes and lengths of PPF on the same fresh concrete, indicating that this combination of fibers leads to decrease both the plastic viscosity and the constant viscous for all mixtures comparing to that of concrete mixtures with one fiber type.
1. Introduction
According to ACI Committee report about the fibrous concrete worldwide application, fibers have been widely used in concrete all over the world. Indeed, large and interesting projects were established with the use of fiber-reinforced concrete (FRC), such as demountable panels for parking garages, runway slabs and nuclear waste container [1,2].
4. Concluding
remarks This study investigates the PPF effect on both rheological and tribological behaviors of fresh concrete. Therefore 4 series of formulation have been done, where the concrete rheological and tribological behavior was evaluated without and with the addition of different lengths (19, 30, 54 mm) and dosages (0.12; 0.24; 0.36%) of PPF. The inclusion of fibers in mixtures induced a workability loss besides a higher viscosity and viscous constant. Thus, a superplasticizer was added in order to enhance the fresh state concrete parameters.
