Improving the short- and long-term cracking behavior of asphalt concrete (AC) under modes III, I/III, and I using New Jig Coal Waste Powder (NJCWP) as a filler replacement

The coupling influence of the long-term repeated loading and time-dependent environmental conditions has led to the formation of low-temperature top-down cracks (LTTDC) and intermediate-temperature top-down cracks (ITTDC) in asphalt concrete (AC). Over time and under the above factors, LTTDC and ITTDC spread on the surface of flexible asphalt pavement (FAP) and caused damage called an alligator cracking pattern. Therefore, by controlling the initial source of damage, LTTDC and ITTDC, it can help to boost the FAP quality and decrease maintenance costs. In this study, an environmentally friendly additive called New Jig Coal Waste Powder (NJCWP) was used as a replacement for aggregate filler to improve the performance of AC mixtures against LTTDC and ITTDC cracks. For this purpose, AC mixtures containing 100 % aggregate filler were compared with AC mixtures containing 50 %NJCWP+ 50 % aggregate filler and AC mixtures containing 100 % NJCWP. AC mixtures were fabricated in the laboratory as edge-notched disc bend (ENDB) specimens to test the fracture behavior under modes I, I/III, and III at + 15 °C (to simulate ITTDC) and −15 °C (to simulate LTTDC). Finally, to simulate the long-term specification of AC mixtures under FAP conditions, ENDB specimens were tested under two conditions, 0 and 1 freeze-thaw (F-T) cycles. The findings of short- and long-term fracture tests revealed that the AC mixture comprising 50 % aggregate filler + 50 % NJCWP had better fracture indices under modes I, I/III, and III compared to the AC mixture containing aggregate filler and the AC mixture with 100 % NJCWP replacement percentage. At ± 15 °C, fracture toughness and fracture stiffness were improved. Regarding flexibility, experimental findings showed that the brittleness of AC mixtures with 50 % and 100 % NJCWP replacement percentages increased slightly at low temperatures (under different modes). A threshold of 20 % was considered for the maximum decrease in CRI at low temperatures, without significantly affecting the reduction in FE . However, the flexibility of AC mixes containing NJCWP exhibited varying trends: it increased under mode I, decreased under mode I/III, and decreased under mode III. Regarding the effect of loading modes (I, I/III, and III) on the fracture test results, it was documented that the fracture behavior of AC mixtures under modes III, I/III, and I was more critical (under short-term and long-term treatment). Therefore, crack deflection on the pavement surface was a motivating factor in increasing the failure level and increasing maintenance costs. The findings of this study can justify the use of NJCWP in FAP from technical and environmental perspectives in addition to promoting the socio-economics of FAP. • The fracture performance of asphalt concrete (AC) was studied under modes I, I/III, and III using ENDB geometry. • The fracture behavior of AC mixes with 0 %, 50 %, and 100 % NJCWP replacement percentages was compared. • The AC with 50 % NJCWP replacement percentage had better short- and long-term fracture performance. • Modes III and I/III were selected as the most critical cracks based on fracture resistance. • In studying the fracture behavior of asphalt mixes, using Pmax instead of fracture toughness may lead to misleading results.