How Does Heat Affect Asphalt? - Arnold Asphalt

Heat has its own unique effects on asphalt. Here are the most common ones.

Raveling

Raveling works in a downward motion and results in a combination of debris, such as asphalt aggregate and soil, in the damaged area. It can have several causes, including inadequate compaction and separation of the aggregate and binder. The type of asphalt repair used for raveling generally depends on how much of the surface is affected and the degree of damage.

Tracking

Though it’s designed to withstand high temperatures — the new hot mix is several hundred degrees when poured — an extremely hot day can soften the surface to the point where small flecks of asphalt adhere to shoes, tires, and anything else moving across the surface. Tracking may also occur when the curing of a new surface is delayed by hot and humid conditions, as can happen during most Florida summers.

Cracking

Cracking is a common type of asphalt damage caused from prolonged heat exposure. Though cracking is more typical in older surfaces, it can affect new structures that were poorly installed or aren’t properly maintained, such as with regular sealcoat applications. It generally affects surfaces with a regular traffic load, such as parking lots and roads.

Oxidation

Oxidation weakens the entire structure of the asphalt, causing the surface to become brittle. UV radiation from sunlight causes a chemical reaction where the light oils combine into heavier oils which reduces the number of binding oils in the asphalt. As oxidation progresses, cracking and/or raveling becomes more prevalent.

Install Asphalt with A High SRI

Since sealcoat protects asphalt against rain and sunshine, heat damage can be prevented or minimized by reapplying this protectant on schedule. A great time to sealcoat is when the heat is on as it helps the materials bond with the surface. Plus, since the heat lowers the viscosity, it flows into deep cracks and crevices, protecting the surface from the inside out. The solar reflectance index (SRI) of a surface measures how well it can reflect incoming solar heat. The lower the SRI, the more heat absorption while a higher SRI — up to 100 — means more reflectance. Generally, new concrete has a high SRI while fresh asphalt, because of the material’s dark coloration, has a low value.

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