Part of what makes asphalt such a durable paving substance is that, unlike concrete and other road construction materials, it can be effectively "refreshed" through the application of so-called chip seals. Yet the benefits of chip seals remain poorly understood by many. If you would like to learn more about this rejuvenating technique, read on. This article will provide some valuable basic information about asphalt chip seals.

The Basic Idea

Chip seals are used to help revitalize aging asphalt surfaces, thus delaying the degradation and wear to which all asphalt is prone. A chip seal consists of two distinct parts. First, an asphalt binding substance is sprayed onto the surface of the roadway. Then the road is sprinkled with small crushed gravel aggregate—also known as "chips."

The chips are then rolled into the binder. This acts to promote a smoother roadway, with the chips filling in any holes left behind by older aggregate that has worked loose with time. By filling in such cracks and holes in the pavement, a chip seal helps to prevent water from pooling up. It also improves the traction of the roadway, thus providing an extra degree of skid resistance.

How Chip Seal Differs From Seal Coat

Many people struggle to differentiate chip sealing from the technique known as seal coating. While both are strategies for extending the lifespan of an asphalt surface, the principle difference is that a seal coat does not include the application of aggregate chips. In other words, a seal coat consists simply of the sprayed-on binder substance.

This binder substance consists of what is known as an asphalt emulsion—in other words, asphalt that has been diluted with water until it reaches an consistency that can be easily applied with a sprayer. In order to ensure that the asphalt mixes thoroughly with the water, a so-called emulsifying agent must be applied. This agent allows the asphalt molecules to remain evenly suspended in the water.

Installation Process

The first step in installing a chip seal is for a truck equipped with the proper spraying equipment to pass over the roadway while laying down an even layer of binding substance. A truck containing the aggregate chips soon follows behind. Timing is an important part of the chip seal application process. If the chips are not applied to the surface of the pavement soon after the emulsion, the two may not bond properly.

With the chips in place, an asphalt roller passes over the roadway, thus pressing the chips down into the existing pavement. The surface is then allowed to dry thoroughly. Finally, any loose asphalt chips are swept off of the road.