Dopravní stavby - Fakulta stavební - Vysoké učení technické v Brně

12th International Scientific Conference, April 20-22, 2009 Brno, Czech Republic 121with M-09 and waste fibers resulted in increased values of optimum bitumen contents. M-09 and wastefibers also had very little workability. The addition of these fibers into bitumen is extremely difficult[1].2. Experimental setup and repeated creep tests performedRepeated creep tests have been performed to find out the accumulated strains. Creep deformationof specimens was measured as a function of time. Prior to testing, specimens were put into the chamberfor 24 hours at 50°C. To understand the behaviour of the specimens under different loading patterns,different constant stress values of 100, 207 and 500 kPa were chosen. As PP modification was carriedout, utilizing lower stress values like 100 and 207 kPa was not feasible, since under such loading thetertiary creep region could not be observed within reasonable period of time. To differentiate betweenthe control and PP-reinforced samples, a loading level of 500 kPa was chosen as the standard stressvalue. This value very well represents the tire pressure of a loaded truck. Load periods were 500 ms forall of the specimens and the rest periods were 500, 1000, 1500 and 2000 ms, respectively. Fourspecimens were tested for each loading pattern [1].3. Test Results and DiscussionRepeated CreepResults of the most attention deserving repeated creep tests are given in Figures 1&2. First graphpresents the accumulated strain versus, and the second graphs describe the creep stiffness versus pulsecounts. Presented graphs demonstrate the positive effect of PP fibers on the properties of asphalt; PPreinforcedspecimens had considerably longer life under repeated load creep tests when compared tocontrol specimens.Fig. 1. Accumulated strain vs. pulse counts of specimens with a loading pattern of 500ms load - 500 ms rest period [1]Fig. 2. Creep stiffness vs. pulse count of specimens with a loading pattern of 500ms load - 500 ms rest period [1]The life of fiber-reinforced specimens under repeated creep tests are approximately 12 times longerthan the control specimens under the same testing conditions (Figs. 1 and 2). This is a significantdifference showing the positive effect of PP fibers. Figure 1 illustrates the control specimens are