Effects of NiO nanomaterial as a bitumen modifier on asphalt mixtures' performance against fatigue and low-temperature cracking in the presence of de-icer agents

Chloride-based de-icing salts are effective for winter road safety but raise environmental and economic concerns by accelerating asphalt deterioration through runoff, penetration, and chemical erosion. To counteract damage driven by deicer, this study examined nano-nickel oxide (nano-NiO) at 2 % and 4 % by weight as a PG 58–22 and PG 64–16 bitumen additive under moisture exposure caused by three common brine solutions: sodium chloride (NaCl), magnesium chloride (MgCl₂), and calcium chloride (CaCl₂). The experimental program employed semi-circular bending (SCB) tests at low temperatures (-10 and −20 °C), Pull-off tests at intermediate and low temperatures (-20, −10, 15, and 25 °C), and indirect tensile fatigue (ITF) tests at intermediate temperatures (15 and 25 °C). The results demonstrated that moisture conditions induced by de-icing agents significantly worsen the cohesion strength, adhesion resistance, fracture properties, and shorten the fatigue life of asphalt mixtures, with CaCl₂ showing the most detrimental effects. In contrast, incorporating 2 % and 4 % nano-NiO substantially improved these parameters; thus, the nanomaterial enhanced mixture integrity by reinforcing cohesion and adhesion bonds, thereby preventing crack formation and stress concentration. Mixtures modified with nano-NiO demonstrated greater resistance to failure at low temperatures. This was evidenced by an increase in the energy required to create a crack (fracture energy) and an increase in the critical stress intensity at the crack tip required for brittle fracture (fracture toughness). Furthermore, the modified samples showed an increased fatigue life (number of load cycles until final failure). Consequently, modified mixtures exhibited superior fatigue and fracture resistance when exposed to de-icing salts. Based on the statistical analysis, it was determined that bitumen modified with 4 % nano-NiO exhibited the best performance in enhancing bitumen-aggregate adhesion/cohesion at low and intermediate temperatures, improving the mixture's low-temperature fracture properties, and extending its intermediate-temperature fatigue life. Furthermore, the evaluation of the low- and intermediate-temperature performance of the base combinations tested in this study revealed that PG 64–16 bitumen, when used with limestone aggregate, produces a mixture with higher stability against the damaging conditions induced by de-icing chemicals. In summary, the results indicate that HMAs made with PG 64–16 bitumen modified with 4 % nano-NiO and limestone aggregate possess the greatest resistance to fatigue and thermal cracking in corrosive de-icing salt environments. • De-icers caused adhesive/cohesive failure at intermediate and low temperatures. • Nano-NiO improved fatigue performance and bonding strength at mid temperatures. • Nano-NiO boosted fracture resistance and cohesion under low temperature conditions. • Generally, CaCl₂ led to the greatest damage (degradation ranking: CaCl₂ > MgCl₂ > NaCl). • Bitumen grade, aggregate type and temperature drive crack growth with de-icers.