RoadSaver laying slurry seal treatment on asphalt pavement in Napa

Slurry Seal

Slurry Seal Overview

Slurry seal is one of the most versatile of pavement surface treatment systems, providing low cost, rapid usability, and aesthetic value, while correcting minor deficiencies in the pavement surface and preventing further deterioration. When used at the right times, slurry seal can help double the life of an asphalt pavement and save money by preventing minor problems from turning into major ones. Slurry seal is also more eco-friendly and less expensive than many other systems.

Slurry Seal Contractors – CPM

CPM has performed slurry work from Alaska to Florida as well as in many overseas locations. Our primary work area remains the western US with our home office in Sacramento. Our slurry seal work includes city, county, and state roads, highways, airports, and commercial parking lots. Our trained, professional crews use only the highest quality materials mixed specifically for your needs. We use top-of-the-line RoadSaver slurry machines to ensure high performance and dependability, and we calibrate them to ensure that the slurry is being applied according to your mix design.

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Slurry Seal Advantage

Low Cost
Slurry seal is economical to install and highly cost-effective to use.
Correct & Prevent Problems
Many existing deficiencies with aged pavements such as cracking, raveling, loss of profile and/or loss of traction due to flushing or polishing of aggregates, can be corrected with a proper application of slurry seal. Resurfacing with slurry seal also provides a new all-weather, long-lasting surface that offers skid resistance, waterproofing, and improved safety and appearance for your roadway.
Various additives can alter slurry seal, tailoring it to the specific needs of the road surface and weather conditions. Your contractor should work with you to create an appropriate mix design for your needs.

Slurry seal is applied quickly, allowing the pavement to be returned to use in just hours after the application is completed. This is an attractive feature for many roads, highways, airports, and parking areas.
With one application, existing pavement becomes more eye-appealing with a uniform black color and a non-skid texture. A new, dark surface and clean appearance means increased property value, marketing potential, and buyer acceptance.

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What is Slurry Seal?

Slurry seal is a mixture of emulsified asphalt, crushed aggregate, water, and set-control additives such as aluminum sulfate and/or Portland cement. Slurry may also use a variety of polymers to enhance the toughness and tenacity of the finished mix. Which additives are used depends on many factors including location, condition of surface, and the type of surface. Slurry seal is a cold-mix paving system that can remedy a broad range of problems on streets, airfields, parking lots, and driveways.



Pavement Condition Index

Pavement Maintenance Costs-Slurry Seal

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A preventive pavement maintenance strategy is more cost-effective than corrective maintenance. This strategy seeks to save money over time by applying treatments over the life of the pavement to minimize life-cycle costs. The treatments help prevent damage from sunlight, oxidized hardening, water intrusion, and will help reduce the need for routine maintenance and service activities.


Learn about Preventive Maintenance.

Types of Slurry Seal

Slurry Seal Types

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Emulsion of varying composition and setting times are mixed with any one of three grades of aggregates to create slurry seal mixes for specific purposes.

Aggregate types are I (fine), II (general), and III (coarse). Fine aggregate mixtures are used for maximum crack penetration and sealing in low density/low wear traffic areas. Type II aggregates are the most commonly used and are widely employed where moderate to heavy traffic is found. Type II seals the surface, corrects moderate to severe raveling, oxidation and loss of matrix, and improves skid resistance. Type II is typically used on residential streets. Type III corrects more severe surface conditions and provides a heavier, course wearing surface. Type III is typically used on highways.

A slurry seal for nearly any need or condition can be custom-designed to satisfy the most difficult requirements.


Slurry Seal History 

In the early 1930’s, a coating consisting of a mixture of very fine aggregates, asphalt binder and water was laid out on a road in Germany. It proved to be a novel approach, a new and promising technique in maintaining road surfaces — and marked the beginning of slurry seal development.

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Later in that decade, extensive worldwide experimentation began in earnest. But it was not until the 1960’s, with the introduction of improved emulsifiers and continuous flow machines, that real interest was shown in the usage of slurry seal for a wide variety of applications.

Continuing advancements in mixing methods, emulsions and machinery have made slurry seal today’s choice in providing highly durable, low cost paving and surface maintenance. As a treatment for everything from residential driveways to public roads, highways, airport runways, parking lots and a multitude of other paved surfaces, slurry seal is now used extensively throughout the world. Local, state and federal agencies — including the military — have a growing and ongoing commitment to the use of slurry seal in their maintenance programs, attesting to its effectiveness and economy.


Making Slurry Seal

Slurry is made in the specially designed RoadSaver II and RoadSaver IIIG slurry and micro surfacing machines manufactured by Rayner Equipment Systems. 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.

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Slurry is made quickly and accurately at the project site. Mixing and spreading are accomplished in one continuous operation, with the surface capable of being reopened to travel within a few hours.

Shown below are the materials and percent quantities for a Type I slurry seal:

Aggregate ~77%
Emulsified Asphalt ~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, 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.

Additive Effect on slurry seal
Aluminum Sulfate Retards curing time
Portland cement Retards or increases curing time
Latex Increases toughness/tenacity

Figure II. Slurry Seal curing agents

Latex is used to increase the tensile strength (or breaking strength) of the slurry when it is 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.

Download the ISSA’s guidelines for slurry seal.

Slurry guidelines from ISSA

RoadSaver Laying Slurry

Applying Slurry Seal 

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Slurry Seal is applied to an existing pavement surface by means of a spreader box. 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 is 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 before slurry applications, barricade the street, inspect the operation in progress for uniformity, clean metal utility covers after application and complete slurry seal spreading in any area inaccessible to the spreader box.


Making Asphalt Emulsion

Asphalt emulsion is made from asphalt oil and emulsifier. An emulsion is a system consisting of asphalt oil with an emulsifier in water (which cannot mix with asphalt oil) in droplets larger than can usually stay in suspension.
The asphalt emulsion is manufactured with hot asphalt oil (210° F; 98.89° C) that is run through a colloid mill with the soap or emulsifier solution. The colloid mill grinds the asphalt oil into particles small enough to be held in suspension by the emulsifier. The product is then stored in large tanks and shipped to customers. It usually must be delivered at temperatures between 120° F (48.89° C) and 150° F (65.56° C).

Contact an Expert

to learn more about slurry seal or any of our
pavement preservation processes.

Contact Us Now!