Issue 50

M. Ameri et alii, Frattura ed Integrità Strutturale, 50 (2019) 149-162; DOI: 10.3221/IGF-ESIS.50.14

In general, it could be stated that there is no significant change in the use of glass fibers, but if the glass fiber is used, the relative improvement will be achieved; although; if more glass fiber is used, the Marshall stability will be decreased. At best, adding 0.1% glass fiber resulted in a 13% increase in the Marshall stability. Previous studies showed that adding glass fiber to the asphalt mixture causes 45% increase in the Marshall stability. On the other hand, according to research, the addition of fiber to the asphalt mixture decreases the parameter by 10%. It could be concluded that more precise research is needed on the use of glass fiber in the asphalt mixtures. Moreover, figure 7-10 show the result of experimental test which were obtained from laboratory test and ANFIS method . The results of ANFIS are close to experimental test and that means this way can predict experimental result correctly. ANFIS has been employed as neural network in some other previous researchers [19] and in these studies, also this relationship ( proximity between laboratory and numerical data shows the efficiency of ANFIS method.

Figure 5 : Flow value for different samples

Flow value Fig. 5 presents the values for the flow in the control and modified samples. As can be seen, there will generally be an increase in the flow value when using the fibers. The use of 0.3% basalt fibers led to a 10% increase in the flow value. The glass fibers also increased the flow value, so that the flow value for the samples made with 0.3% glass fiber reached 4.2 mm. On the other hand, it is observed that for the percentages higher than 0.3% fiber, the flow value exceeded the allowable limits of the regulation and the flow value was significantly increased, so that for the samples made with 0.7% fibers (whether basalt or glass), an increase about 50% is achieved. As mentioned earlier, based on the results of the Marshall Stability and flow, 0.5 and 0.7% fibers were removed and the remaining tests were performed using other percentages. In order to justify the flow increase in the case of using basalt and glass, two approaches are considered: it seems that even though the basalt and glass fibers have a high melting temperature, the surface of the fiber melts during the asphalt curing and increases the viscosity of bitumen. This causes the bitumen to be less adsorbed onto the surface of the aggregates and to remain in the space between the aggregates. In this way, the presence of additional bitumen in aggregates increased the flow of samples. On the other hand, the flow, in fact, is the rate of sample deformation at the moment of failure. Now, the fibers cause the bonding and adhesion of different parts of the sample to each other and make the specimen exhibit more deformation at the moment of failure. Previous studies have discussed the glass fibers and their application to hot-mix asphalt concrete. The flow number is increased in previous studies for increasing the percentage of glass fiber. For example, Taherkhani (2016) added glass fiber and Nano clay in the mix design of the hot-mix asphalt concrete, adding 0.2, 0.4 and 0.6 glass fiber. In this research, it was tried by providing more percentages (0.1-0.7) and comparing the results to show that the flow number is increased with the use of glass fiber in the mix design. The increase for 0.6 glass fibers is 1.16 times the control sample in the Taherkhani study [20], and in this study, it is approximately 1.4 times. It could be stated that the addition of glass fibers led to the maximization of the flow number. On the other hand, the results of previous research, such as Nihat Morova [21] on the use of basalt in the mix design for asphalt concrete. This research indicates an increase in the flow number for adding

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