Evaluating the Fatigue Resistance of the Innovative Modified‐Reinforced Composite Asphalt Mixture

Abstract

Fatigue failure is regarded as one of the most common failures in the road pavement and necessitates spending huge cost annually to maintain the road. Asphalt binder modification and asphalt mixture reinforcement are among the commonly used methods to increase the pavement resistance to a failure caused by fatigue. By proposing a modified-reinforced composite hot mix asphalt (MRC-HMA), the present study aimed to examine the fatigue life of this mixture with one of the most traditional methods (i.e., four-point bending beam fatigue test) and compare it at constant strain conditions and the strain levels of 500, 700, and 900 μ ε and a temperature of 20 ± 0.8 ° C to that of the other three specimens, including control specimens, geogrid-reinforced (GR-HMA) specimens, and nanosilica-modified (NSM-HMA) specimens with 5% nanosilica. In all experiments, the condition to reach the failure stage was assumed equivalent to a 50% reduction in the stiffness coefficient in each load repetition, and the load was applied semisinusoidal at a frequency of 10 Hz without rest. The results showed that the MRC-HMA mixture improved the fatigue life at the strain level of 500 μ s by about 701, 172.5, and 156.4% compared to the control, NSM-HMA, and GR-HMA specimens, respectively. Based on the results, the use of GR-HMA specimens has almost the same results as NSM-HMA ones, but the use of the MRC-HMA mixture can significantly increase the fatigue life of MRC-HMA in all three levels of strain compared to all specimens studied in the present study. Thus, the introduced mixture can be a proper choice for pavements with heavy or light (with a large amount) traffic loads, which usually have a vast adverse effect on the fatigue behaviour of asphalt mixtures.

Evaluation of Fatigue Behavior of Asphalt Layers Containing Nanosilica Modified Tack Coat

“…where σ t represents the maximum tensile stress in kPa, P indicates the load on the specimen in kN, b shows the average width of the specimen in mm, h displays the average height of the specimen in mm, G 0 demonstrates the distance between supports in mm, and G i depicts the distance between the loading clamps. Moreover, ε t is the tensile strain, δ is the mean displacement in the middle of the beam in millimeters, E s is the flexural stiffness in MPa, E is the elasticity modulus in MPa, v is Poisson's coefficient, and K is the real shear stress ratio in terms of average shear stress, which is assumed 1.5 [15]. e IF parameter is related to the recovery coefficient, which shows the number of loading cycles at the turning point of the flexural stiffness diagram.…”

“…where N th f represents the number of loading cycles of the specimen i th, and N control f indicates the number of loading cycles of the control specimen. e higher the value of IF, the greater the ability of the asphalt mixture to delay crack propagation [15].…”

“…Regarding the formation of strong networks in bitumen, nanomaterials often cause bitumen stiffness, increase rutting resistance, enhance the resilience modulus of asphalt, and in some cases, increase the fatigue life of bitumen and asphalt mixtures. In this regard, hydrated nanolime, nanoclay, carbon nanofibres, and nanosilica are among the nanomaterials added to bitumen or asphalt mixtures as modifiers in recent years [15][16][17].…”

“…e modification of bitumen with nanosilica increases viscosity, softening point, and elasticity modulus and decreases ductility. e application of nanosilica modified bitumen improves some properties such as dynamic modulus and viscosity, increases the Marshall resistance and the stiffness modulus, and causes less sensitivity to temperature variation [15].…”

Determination of water sensitivity of nanosilica added hot mix asphalt

“…When the studies using nanosilica additive in asphalt modification were examined, it was stated that nanosilica increased the viscosity, softening point and elasticity modulus of asphalt, while decreasing its consistency and ductility [12][13][14]. In other studies, it was stated that the rheological properties of nanosilica-modified binders improved and their temperature sensitivity decreased [13,15].…”