Slurry Seal

What is a Slurry Seal?

Slurry Seal is a cold-mix paving system that can remedy a broad range of problems on streets, airfields, parking lots and driveways. Think of Slurry as an Industrial Grade Asphalt Surfacing.

The principal materials used to create slurry seal are aggregate, asphalt emulsion and fillers, which are mixed together according to a laboratory’s design mix formula. Water is also added for workability.

Advantages of Slurry Seal

As the most versatile of any pavement surface treatment system, slurry seal is also unique in its ability to deposit a durable bituminous mixture in accordance with the demands of a variably textured surface – filling cracks and voids, sealing the surface weather-tight, and providing color and texture delineation in a single pass.

How Slurry Seal is Made

Slurry is made in the specially designed RoadSaver II Microsurfacing machine manufactured by CPM. This equipment carries a quantity of unmixed materials that are blended together in a continuous flow pugmill. The use of this technologically advanced machinery insures a smooth consistently uniform mixture.

Slurry is made quickly and accurately at the project site. Mixing and spreading are accomplished in one continuous operation, with the surface being ready to reopened to travel within a few hours. Shown below are the materials and percent quantities for a type I slurry seal:

Emulsified Asphalt Oil~12 - 16%
Water~5 – 10%
Aluminum Sulfate (or other additive)~1/2 – 2%

Figure 1. Slurry Seal type I mix design

When the slurry seal is cured, the only components left are the aggregate and asphalt oil. The water is used only to aid in working with the mix as it is applied. Aluminum sulfate, portland cement, lime, or other additives are curing agents that either speed up or slow down the curing process. Figure II shows the effects that different agents have on the mix.

AdditiveEffect on slurry Seal
Aluminum SulfateRetards Curing Time
Portland CementIncreases Curing Time

Figure II. Slurry Seal curing agents

Latex is used to increase the tensile strength (or breaking strength) of the slurry when is it cured. This helps the slurry resist cracking or separating as traffic squeezes and pushes on the asphalt pavement. Carbon Black is a cosmetic additive only. It is there to make the final slurry surface a darker black.

How Slurry Seal is Applied

Slurry Seal is applied to an existing pavement surface by means of a spreader box linked to the RoadSaver II slurry mixing unit. Slurry is introduced into the spreader box, which then lays down the slurry coating as the mixer/spreader is driven forward.

The spreader box is capable of spreading the slurry seal over the width of a traffic lane in a single pass, and I constructed so that close contact with the existing surface is maintained. This insures uniform application of the new coating on a variety of configurations encompassing various crown shapes, super-elevated and shoulder slopes.

Trained operators continually monitor the automatic mixing procedure. Other personnel clean the surface slurry applications, barricade the street, inspect the operation in progress for uniformity, clean metal utility cover after application and complete slurry seal spreading in any area inaccessible to the spreader box.