Journal of King Saud University: Engineering Sciences (Jul 2021)
Investigating the effects on creep and fatigue behavior of asphalt mixtures with recycled materials as fillers
Abstract
Following the increase in the number and quantity of waste materials and their negative impact on the environment, this research has sought to examine the benefits of recycling these waste materials and check their impact on the creep and fatigue of asphalt concrete mixture when they are added as fillers. Four waste materials were used in the tests conducted: waste toner, waste medical ash, Waste Electrical Arc Furnace Dust (EAFD), and waste tire rubber. Limestone was added as a control material. Adding these waste materials as fillers was made by the Marshall Test method. Then, the Universal Testing Machine (UTM) was used to simulate creep (dynamic and static) and fatigue tests. Two different temperatures were used (25, 40 °C), and for the dynamic creep, three different loading frequencies were utilized (1, 4 and 8 Hz) to simulate vehicle speeds of 20, 40 and 60 miles/hr. respectively. Based on the laboratory test results, testing temperature and loading frequency for each type of filler had a significant influence on the accumulated strain, creep stiffness, and resilient modulus. Consequently, the increase in loading frequency from 1 to 8 Hz meant speed increase, and thus decreased-time of contact between the stress of the load and asphalt concrete mixture. In this case, rutting decreased with the increase of Hz. Thus, axial micro-strain increased with time at loading frequency and temperature, showing that waste toner was the best filler that could be added to the asphalt concrete mixture. Similarly, in static creep test, accumulated strain increased with time at different levels of temperature for all types of fillers. Conversely, creep stiffness decreased with time at different levels of temperature for all types of fillers. Experimental results on fatigue indicated that for the best filler investigation, a linear relationship was obtained between logarithm strain and logarithm number of cycles (Nf). As a result, the waste toner as filler was the best filler as it had the highest fatigue life for the tested mix design.
