Open-Graded Asphalt Mixes

Anyone involved with a highway construction project can tell you that each process and material must comply with at least one product specification. These specifications require that a material be developed to meet particular structural and aesthetic needs.

Open-graded asphalt mixes, commonly referred to as “popcorn mixes” are one product developed by the construction industry to help promote maximum highway safety. Open-graded asphalt mixes are generally characterized by a large percentage of one size of coarse aggregate-usually ½ or 3⁄8 inch maximum particle size-little or no fines and a high percentage of air voids in the mix.

The voids provide channels between the angular surfaces of the aggregate to allow rapid drainage of surface water, such as rain, out to the shoulders. This prevents hydro-planing and provides maximum skid resistance under all weather conditions. Other benefits of the channeling effect are reduction of tire spray, improved visibility of stripes and pavement markers and reduced glare from headlights while driving at night under wet road conditions. In addition to safety benefits, there are also cost benefits. Open-graded mixes are placed in thin layers, using a minimum amount of material.

Use of an open-graded asphalt mix provides a cost-effective means for correcting minor surface irregularities. The benefit is two-fold: better riding quality of our roads which significantly improves overall highway safety.