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Pavement Maintenance - Slurry Seal

Slurry seal is a mixture of emulsified asphalt oil, rock, water, and additives such as aluminum sulfate, Portland cement, lime, latex or carbon black. Which additives are used depends on many factors including location, condition of surface, and the type of surface. All these factors are considered when the laboratory designs a mix. Our machines are calibrated to ensure that the slurry seal is being applied according to the mix design.   Our professional crews work in the four state region including California, Nevada, Arizona, and Oregon. Our slurry seal work includes city, county, and state roads, airports, and commercial parking lots. If we are in your area, we can even slurry seal your driveway or small parking lot for less than you might expect. Capabilities include: Road Slurry Seal Microsurfacing Rut Filling

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Slurry Seal

What is 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.

Low Cost

Economical to install, highly cost effective to use.

Rapid Usability

Easy, swift application of a new overlay makes slurry especially attractive for rehabilitating busy thoroughfares, parking lots and airport runways. The new surface is ready to use in just hours after application.

Correcting & Preventing Problems

Existing distresses in older pavements - surface cracking, raveling, loss of matrix, increased water and air permeability and lack of friction due to flushing or aggregate polishing - can be corrected through a slurry application. Waterproofing is also achieved, preventing further deterioration. An all-weather, long lasting surface is created that offers skid resistance and improved handling characteristics for drivers.

Aesthetic Value

With one simple application, existing pavement receives a new wearing surface of uniform black color and texture. Enhanced appearance means increased property value, marketing potential and buyer acceptance. Thoroughfares, shopping center parking lots and other public or commercial pavements treated with slurry seal become more attractive and eye-appealing.

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Pavement Maintenance Costs - Slurry Seal

A preventative maintenance strategy is an organized, systematic process for applying a series of preventative maintenance treatments over the life of the pavement to minimize life-cycle costs. It is also a program strategy intended to arrest light deterioration, retard progressive failures, and reduce the need for routine maintenance and service activities.

Recent studies support the effectiveness of preventative maintenance. The Strategic Highway Research Program (SHRP) Project H-101, Experiment SPS-3 and the National Cooperative Highway Research Program (NCHRP) Synthesis 223, Cost Effective Preventative Maintenance both found slurry seal to be a useful treatment.

The NCHRP Synthesis, a survey of sixty state, province, and local transportation agencies, confirms that the most cost effective pavement management strategy - which results in the highest pavement condition rating - is to perform preventative maintenance activities on the better-rated pavements first and then fund the rehabilitation of the poorer-rated pavements. The funding strategy that addresses the worst pavements first is the least cost effective.

Slurry seal is a perfect fit for your pavement maintenance program.

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Slurry Seal Types

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 III corrects more severe surface conditions and provides a course wearing surface.

Microsurfacing is a special kind of slurry seal that wears better and sets faster than  standard slurry surfacing. This material uses special asphalt emulsion and is usually more expensive.

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

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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.

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.

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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:

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.

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.

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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 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.

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How Asphalt Emulsion is Made

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) 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 and 150° F.

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