How Temperature Influences Asphalt Pavement's Functional Performance
As climate patterns shift and extreme weather becomes more common, it is increasingly important to consider temperature resilience in pavement design and construction to ensure long-lasting infrastructure.
Dr. Ambika Behl - Senior Principal Scientist - Flexible Pavement Division, CSIR-CRRI, New Delhi

Introduction
Dr. Fertel of Cleveland Clinic in an article (2019) titled “Ooh! Ouch! That Scorching Hot Pavement Can Actually Burn Your Skin” recommends doing a touch test of playground to make sure it’s not too hot before letting kids play on it. It might be a myth that you can fry an egg on a hot pavement, but it’s a fact that you can burn your skin on one. A recent study found that this is especially true in areas of direct sunlight when the air temperature exceeds 95 degrees Fahrenheit. Andrea Thompson of Scientific American in her article (2023) “New NASA Heat Map Shows Scorching Streets That Can Burn Skin in Seconds” reported that there is potential risk of getting burns on touching the pavement for 1-2 minutes amid temperatures above 110 degrees Fahrenheit (43 degrees Celsius). India’s Times Now had reported in an article in 2023 about how roads are melting in Ahmedabad (figure 1) and the difficulty this is posing for commuters.


In the last few years, due to global warming, the atmospheric temperatures have risen a lot, leading to very high pavement surface temperatures which directly impact the performance of an asphalt pavement. As per the heat map of India given by WRI India (figure 2), major parts of India gets temperature of more than 50OC, which means pavements in these areas can be exposed to as high as 65-70OC in peak summer days. Recently, team CRRI was working on a project in Uttar Pradesh in the month of June, during which, the pavement temperature was recorded as high as 75OC (figure 3). Don’t you think that if a person touches the pavement surface for 1-2 minutes, he will surely get a heat burn? It’s an alarming high temperature for roads. Are our pavements able to withstand such high temperatures? What will be the effect of high temperature coupled with the traffic load on the pavement? This article explores how both high and low temperatures influence the structural integrity and functional performance of asphalt pavements.
Temperature and its Effect on Pavements
Asphalt pavements are widely used for constructing roads, highways, and parking lots due to their flexibility, cost-effectiveness, and ability to withstand significant traffic loads. However, temperature variations can greatly affect the performance, durability, and longevity of asphalt pavements. Usually, the pavement temperature is much higher than that of the ambient air, and sometimes reach 70OC or more. It’s well known that asphalt is a heat-absorbing material and in recent years, with the global warming, air temperature is generally on the rise, and many parts of India experience the high-temperature weather. In last 2-3 years we saw many pavement failures in the country and damage was rutting failure. The complex modulus of asphalt binder decreases with the increasing of the temperature. In fact, with increasing temperature there is major decline in the stability and the structural strength of asphalt concrete. The higher the temperature is, the lower the stiffness modulus and rutting resistance of the asphalt pavement are.

i. Effect of High Temperatures on Asphalt Pavements
Asphalt is a thermoplastic material, meaning it softens under high temperatures and becomes more rigid at lower temperatures. When exposed to high temperatures, asphalt pavements can suffer from various forms of distress:
- Softening and Rutting: During hot weather, especially in summer, the temperature of asphalt pavements can rise significantly. The asphalt binder, which holds the aggregate particles together, softens at elevated temperatures, leading to rutting. Rutting occurs when the weight of vehicles, particularly heavy trucks, deforms the soft asphalt surface, creating depressions or grooves along the pavement.
- Bleeding and Flushing: Bleeding is a phenomenon where excess asphalt binder rises to the surface due to the softening caused by heat. This results in a shiny, sticky layer on the pavement that can reduce traction and make the surface slippery. Flushing, a related issue, occurs when asphalt migrates to the surface and fills surface voids, creating a smooth, dangerous texture.
- Oxidation and Aging: Prolonged exposure to high temperatures accelerates the oxidation process of the asphalt binder. Oxidation makes the binder more brittle and prone to cracking. Over time, this can lead to surface cracks and ultimately affect the overall lifespan of the pavement.

ii. Effect of Low Temperatures on Asphalt Pavements
Cold weather presents its own challenges for asphalt pavements, often leading to cracking and structural damage. As temperatures drop, the asphalt material contracts, and this can result in:
- Thermal Cracking: Asphalt pavements are susceptible to thermal cracking during cold weather due to the contraction of the material. Low temperatures cause the asphalt binder to lose flexibility, and when the pavement contracts, it may not have enough strength to resist cracking. These cracks can allow moisture to infiltrate the pavement structure, leading to further damage.
- Frost Heaving: In regions with freezing temperatures, water present in the subgrade or base layers of the pavement can freeze, causing frost heaving. The expansion of frozen water can lift sections of the pavement, leading to an uneven surface. When the ice thaws, it leaves voids that weaken the pavement, resulting in cracks, potholes, and depressions.
- Moisture Damage and Freeze-Thaw Cycles: Low temperatures often come with precipitation, which can infiltrate the pavement through cracks or surface imperfections. Water trapped in the pavement expands when it freezes, exerting pressure on the pavement structure. During freeze-thaw cycles, this expansion and contraction can worsen existing cracks and cause new damage, ultimately leading to pavement failure.
Rapid temperature fluctuations, such as those experienced in some climates where days are warm and nights are cold, can also degrade asphalt pavements. These variations cause expansion and contraction cycles that place stress on the material, leading to fatigue and cracking. Over time, these repetitive temperature-induced stresses can accumulate, reducing the structural integrity of the pavement.

Rutting Failure in Asphalt Pavements Due to High Temperature
Rutting is one of the most common forms of distress in asphalt pavements, particularly in regions where high temperatures are prevalent. It manifests as longitudinal depressions along the wheel paths of the road. This failure is caused primarily by the deformation of the asphalt layer due to repeated traffic loads, and it is exacerbated by elevated temperatures. High temperatures soften the asphalt binder, making it more susceptible to permanent deformation under heavy vehicle loads.

Rutting is generally caused by a combination of factors, including material properties, traffic loads, and environmental conditions. High temperatures play a particularly significant role in accelerating the development of rutting. Asphalt is a viscoelastic material, meaning it behaves both as a solid and a fluid depending on temperature. At high temperatures, the asphalt binder softens and becomes more fluid-like, reducing its ability to hold aggregate particles together under traffic loads. This leads to plastic deformation, where the pavement cannot fully recover after a load is applied. With each passing vehicle, especially heavy trucks, the softened asphalt deforms and causes rutting. In regions with consistently high temperatures, especially during summer months, the surface temperature of asphalt pavements can rise dramatically, sometimes exceeding 60°C. These elevated temperatures soften the binder and accelerate the rutting process. Pavements in hot climates are at greater risk if they are not designed with heat-resistant materials or proper compaction.

Due to its viscoelastic nature, temperature-dependent properties, and shear-dependent viscosity, bitumen is classified as a non-Newtonian fluid. Its behaviour is complex and changes based on external factors like temperature, extent of loading, rate of loading, time, and shear rate. A graphical representation of this phenomena is given in Fig. 4.
To choose the correct binder and design for a pavement, it is very important for design engineer to understand the rheology of bitumen. Recently MoRTH has provided a table as reference for design engineer to chose bitumen w.r.t to the air temperature and traffic loading. The table 1 has been taken from MoRTH notification issued on 19th April 2024
Pictures given here are from 5 national highways where the rutting failure was observed, CRRI was involved in the root cause analysis of the rutting failure and accordingly rehabilitation methodology was recommended. All of these sections lie in high temperature zone and one of the reasons for rutting was improper selection of binder in concern to high temperature. A bitumen which has softening point 55-58OC, that can never withstand pavement temperature 65-70OC.

Mitigation Strategies for Temperature-Related Damage
There are several ways to mitigate the effects of temperature on asphalt pavements:
- Using Temperature-Resistant Asphalt Mixes: Engineers can design asphalt mixes to better withstand temperature extremes. For instance, adding polymers to the asphalt binder improves its elasticity and temperature resistance, helping the pavement perform better in both hot and cold conditions. Polymer modified binders show much improved resistance to rutting failure.
- Surface Treatments and Sealants: Applying sealants or surface treatments can protect the asphalt surface from temperature-induced damage. Seal coats help to prevent oxidation and reduce the permeability of the pavement, thus protecting it from moisture infiltration and freeze-thaw damage.
- Proper Drainage Systems: Effective drainage systems can prevent water from accumulating on or below the pavement, which is especially important in cold regions where freeze-thaw cycles are common. By reducing the amount of water that can penetrate the pavement, the risk of frost heave and moisture damage is minimized.
- Timely Maintenance: Regular mainte- nance, such as filling cracks and repairing potholes, can prevent minor temperature-related damage from escalating into major structural issues. Timely interventions can extend the life of asphalt pavements and reduce the overall cost of repairs.
Conclusion
Temperature plays a significant role in the performance and durability of asphalt pavements. High temperatures can soften the asphalt binder, leading to rutting, bleeding, and accelerated aging, while low temperatures can cause thermal cracking, frost heaving, and freeze-thaw damage. Engineers can mitigate these effects by using temperature-resistant materials, improving drainage, and implementing timely maintenance practices.
References:
- Huang, Y. H. (2004). Pavement Analysis and Design. Pearson Prentice Hall.
- National Asphalt Pavement Association. (2021). Asphalt Pavement Guide.
- Asphalt Institute. (2011). The Asphalt Handbook.
- Liu Xingdong and Yang Xiwu, “Analysis of temperature impact to track on asphalt pavement,” Technology of Highway and Transport, (3), pp. 66-69,June 2007.
- Yan Qi-lai, Huang Xiao-ming and Zhao Yong-li, “The effect of environment temperature on the high temperature stabilities of asphalt mixture,” Journal of Heilongjiang Institute of Technology, vol. 19(4), pp. 25-28, December 2005.