Type 2 asphalt (often written “Type II”) is a designation used by state transportation departments and engineering specifications to describe a specific grade of hot mix asphalt or slurry seal mixture. It is not a single universal product. The term refers to a classification within a grading system, and its exact meaning depends on whether you’re looking at a hot mix asphalt (HMA) pavement specification or a slurry seal specification for pavement maintenance. In both cases, Type II sits in the middle of the grading scale, making it one of the most commonly specified asphalt types for everyday road surfaces and residential projects.
Type II Hot Mix Asphalt
In the hot mix asphalt world, Type II typically refers to a dense-graded surface mix with a relatively fine aggregate size. Georgia’s Department of Transportation, for example, designates a “9.5 Type II” mix, where 9.5 refers to the nominal maximum aggregate size in millimeters (roughly three-eighths of an inch). This produces a smooth, tightly packed surface that works well for residential streets, parking lots, and lighter-traffic roadways.
Dense-graded mixes like Type II are designed so that the range of stone, sand, and filler particles fit closely together, leaving minimal air voids. The Federal Highway Administration notes that dense-graded asphalt mixtures, when designed with appropriate materials, typically provide adequate surface texture for both drainage and tire grip. The result is a relatively smooth finish compared to coarser, open-graded mixes used on highways.
Layer Thickness and Installation
Type II hot mix asphalt is laid in thin lifts. Georgia DOT specifications call for a minimum layer thickness of 1⅛ inches and a maximum of 1½ inches per lift, with a recommended thickness of about 1¼ inches (roughly 135 pounds per square yard of material). The maximum total thickness across multiple lifts is 4 inches. These numbers make Type II a surface or top-course material rather than a base layer, which would use coarser, thicker mixes.
Temperature control matters during installation. For standard unmodified asphalt binders, compaction temperatures typically fall between 127°C and 147°C (about 260°F to 297°F). Polymer-modified binders, which add flexibility and durability, may require higher temperatures, sometimes up to 167°C (333°F). If the mix cools too much before compaction, the pavement won’t achieve proper density and will deteriorate faster.
Type II Slurry Seal
The term “Type II” also appears in slurry seal specifications, which is a different application entirely. A slurry seal is a thin maintenance coating applied over existing pavement to seal cracks, improve the riding surface, and extend the road’s life. It’s not a structural layer. Type II slurry seal consists of an asphalt emulsion (a liquid asphalt product called CQS-1h), mineral aggregate, water, and chemical additives, all mixed together and spread in a thin layer over the old pavement.
Type II slurry is commonly used for transverse leveling, which means filling in dips and recessed joints where the underlying pavement has settled or deteriorated. Municipal road maintenance programs frequently specify Type II slurry because its aggregate gradation is fine enough for a smooth finish but coarse enough to fill minor surface defects. If you’ve seen a road crew spreading a dark, wet-looking layer over an existing street that dries within a few hours, that’s often a slurry seal application.
How Type II Compares to Other Types
Asphalt classification systems generally run from Type I through Type III or higher, with the numbers reflecting aggregate size and intended use:
- Type I uses the finest aggregate. It’s suited for very low-traffic areas, bike paths, or as a thin seal coat on surfaces with only minor wear.
- Type II uses a medium aggregate gradation. It handles moderate traffic volumes and is the most versatile option for municipal streets, subdivision roads, and parking lots.
- Type III uses coarser aggregate. It’s intended for heavier traffic or surfaces with more significant damage that needs filling.
Type II lands in the sweet spot for most residential and commercial paving projects, which is why it appears so frequently on contractor bids and city maintenance schedules.
Expected Lifespan
How long Type II asphalt lasts depends heavily on traffic volume, climate, and maintenance. The Asphalt Institute reports that hot mix asphalt pavements are generally designed for a 20-year initial service life, and many exceed that with routine upkeep like crack sealing and thin overlays. After major rehabilitation, the second phase of performance often lasts another 15 years or more.
Climate plays a significant role. In wet-freeze environments (cold winters with rain or snow), pavements under moderate traffic loads may show meaningful deterioration after about 9 to 10 years without maintenance. In dry, mild climates, the same pavement can last well over 20 years. A Type II surface course applied at the proper thickness and compacted at the right temperature will generally hit the upper end of these ranges, especially with periodic sealcoating or crack repairs every few years.
Why You Might See This Term
If you encountered “Type 2 asphalt” on a city notice, a paving contract, or a project specification, it most likely refers to either a hot mix surface course for new paving or resurfacing, or a slurry seal mixture for road maintenance. In both cases, it signals a mid-grade product designed for typical residential or moderate-traffic use. It’s not a specialty material for highways or airports, and it’s not the thinnest possible treatment for a lightly used path. It’s the standard workhorse grade for the roads most people drive on every day.