Treatment Types

What?

Crack seal consists of a heated, adhesive blend of rubber and asphalt. This process fills the cracks only and is not intended to resurface the entire street. The sealant forms a long-lasting, resilient seal that is flexible and expandable in varying and extreme pavement temperatures. It takes only a few minutes for each filled crack to cool, allowing cars to pass over the treated area. Impacts to residents and motorists are minimal with crack seal maintenance.

The formation of cracks in asphalt pavement is a result of the combined effects of traffic and temperature variations. Cracks are a normal occurrence as asphalt ages, thus becoming less pliable and unable to withstand the strains of these environmental effects. Preventive maintenance measures such as crack sealing can significantly prolong the road's lifespan and enhance the driving experience for motorists.

Why?

Crack sealing is performed to prevent water from infiltrating our street surfaces through cracks in the road surface. Over time the water will disturb or break down the road base causing additional cracking, alligatoring (extreme cracking) and eventually base failure (sinking and crumbling) of the road surface. If the streets are allowed to alligator or even worse, base failure, this would require a base repair or reconstruction of the street to bring it back to a fair or better state.

Proper crack sealing is without question the most cost effective and important part of our preventative maintenance program. Cracks are prepared for sealing using highly compressed air to blow out and clean the cracks; a torch is also used to burn vegetation that may be growing in these crevices. Cracks are then sealed with a very hot Asphaltic rubber that adheres to the walls and fills the cracks.

When?

On existing asphalt pavement, crack seals are typically applied on either an intermittent or cyclical basis. Location, weather, traffic loading, and pavement conditions are factors used to determine if a crack seal application is appropriate.

How?

Crack seals are applied by workers using hoses connected to a large heated tank that contains the crack sealing material.

What?

A slurry seal is the application of a mixture of water, asphalt emulsion, aggregate (very small crushed rock), and additives to an existing asphalt pavement surface. This combined mixture of the emulsion and aggregates represents "slurry." Polymer is commonly added to the asphalt emulsion to provide better mixture properties. The placement of this mixture on existing pavement is the "seal" as it is intended to seal the pavement surface. Slurry seals are generally used on residential streets.

Why?

Slurry seal is applied in order to help preserve and protect the underlying pavement structure and provide a new driving surface. Roads chosen for slurry seal applications generally have low to moderate distress and narrow crack width. Slurry seal applications serve to seal the cracks, restore lost flexibility to the pavement surface, provide a deep, rich black pavement surface color, and help preserve the underlying pavement structure.

Depending on the condition of the road, the removal and replacement of failed sections of the road are done prior to the slurry seal. This prep work is often referred to as "dig outs".

When?

Slurry seal is typically applied on either an intermittent or cyclical basis. Location, weather, traffic loading, and pavement conditions are factors used to determine if a slurry seal application is appropriate. Roadways selected for slurry seal treatment are commonly those which have slight to moderate distress, no rutting, and generally narrow crack widths, and where a slurry seal treatment would help extend the pavement life until resurfacing becomes necessary.

Roadways chosen for cyclical slurry seal applications would typically be treated every five to seven years.

How?

The asphalt emulsion and the aggregates are mixed in, and applied using, a purposely built truck, generally referred to as a "slurry truck." Yes, I know, that's rather obvious, but I didn't make it up!

Slurry trucks contain various compartments which hold the aggregate (fine crushed rock), water, polymer modified emulsion, and other additives, which are mixed in the on-board mixer. The slurry mixture flows out of the rear of the truck and onto the pavement within the confines of a box attached to the rear of the truck. The box serves to distribute the slurry mixture over the pavement. Workers with squeegees follow behind and assist in spreading the mixture, correcting areas not properly covered, and keeping the mixture off of concrete improvements such as gutters.

A piece of burlap is often dragged behind the slurry truck with the goal of producing a smooth texture while spreading the slurry seal. The texture of a slurry seal is different than that of asphalt pavement. The texture may have faint lines and be somewhat coarse. In addition, when the slurry is first placed the surface is tender and can be marked up by sudden turning movements. These impressions on the pavement are temporary as seasonal weather and traffic smooth out these imperfections over time.

Once placed slurry seals need 4 to 6 hours to set or harden before the road is open for traffic.

What?

A chip seal is a two-step process which includes first an application of asphalt emulsion and then a layer of crushed rock to an existing asphalt pavement surface. A chip seal gets its name from the "chips" or small crushed rock placed on the surface.

Asphalt emulsions used in chip seal applications contain globules of paving asphalt, water, an "emulsifying agent" or surfactant, polymer, and sometimes a "rejuvenator." Soap is a common form of a surfactant. In washing clothes or dishes, the surfactant helps remove the dirt and suspend the dirt particles in the wash water. Similarly, in asphalt emulsions, the surfactant keeps the paving asphalt globules in suspension until it is applied to the pavement surface when the water in the asphalt emulsion starts to evaporate. The chips (small crushed rocks) are immediately applied after the asphalt emulsion is applied to the pavement surface. The polymer in the asphalt emulsion is a "hardener" which serves to improve the adhesion to the crushed rock and to the pavement surface. A "rejuvenator" is an asphalt or additive which when applied to the existing pavement will slightly soften the pavement it is applied to creating a better bond.

Depending on the condition of the road, the removal and replacement of failed sections of the road are done prior to the chip seal. This prep work is often referred to as "dig outs".

Why?

Chip seals are placed under one of three scenarios, as a "wearing course" meaning vehicles drive directly upon it; as part of a "cape seal" meaning a chip seal is first placed, then covered by slurry seal or microsurfacing; or as an "interlayer" meaning a layer between underlying asphalt pavement and a new asphalt or rubberized asphalt surface.

As asphalt pavement is subjected to traffic loads and as it ages, it oxidizes, becomes more brittle and cracking develops in the pavement structure. A chip seal serves to seal the narrow cracks, help bind together cracked pavement, provide a wearing (driving) surface, and protect the underlying pavement structure. Chip seals used as interlayers serve to retard reflective cracking which develops from the bottom of the pavement structure towards the top.

When?

Roadways chosen for cyclical chip seal applications would typically be treated every seven to ten years. Location, weather, traffic loading, and pavement conditions are factors used to determine if a chip seal application is appropriate. Roadways selected for chip seal treatments are commonly those which have moderate block (or "alligator") cracking which is not spalling (or "popping out"), no rutting, an acceptable ride quality, and in which a chip seal would help extend the pavement life until resurfacing or rehabilitation can be performed.

How?

A distributor truck first applies the asphalt emulsion to help seal the pavement surface. Using an asphalt emulsion is considered a "cold applied" chip seal even though the liquid temperature is typically between 110 and 150 degrees Fahrenheit. No smoke results from the application of emulsified asphalt. If modified paving asphalt is applied, it is considered a "hot applied" chip seal as the liquid application temperature is typically between 325 and 375 degrees Fahrenheit. Smoke will result from the application of modified paving asphalt but should not be of concern. Depending upon formulation, the distributor truck may be equipped with a smoke reduction device which reduces the level of blue smoke emitted. This is normal. These devices are subject to permitting and oversight by the jurisdictional air quality management district.

Immediately following application of the asphalt emulsion, a "chip spreader" follows and applies crushed rock to the top of the asphalt emulsion. A dump truck dumps crushed rock into the chip spreader as it travels. The dump truck appears to be going in reverse but it actually is being towed backward by the chip spreader.

Following chip application, rubber tired rollers follow closely behind. The purpose of the rollers is to push the chips down into the binder and enhance the bond between them. A steel drum roller commonly follows the rubber tired rollers on "hot applied" chip seals.

Depending on the condition of the road, a second chip seal layer may be applied. This is referred to as a double chip seal.

After rolling and once the binder and chips have properly adhered, the surface is swept by power sweepers. The sweepers sweep the loose crushed rock which has not adhered to the underlying asphalt emulsion. Loss of crushed rock due to sweeping is a normal part of the operations. A chip seal would not be successful if the result was areas of the existing pavement not covered by crushed rock. The rate of crushed rock application is intended to result in a thickness of "one rock."

In some instances a "flush coat" is then applied over the chip seal. The flush coat consists of the application of a fog seal (see fog seal) followed by the application of very clean sand. The purpose of the flush coat is to help "lock down" the chips and absorb any excess asphalt emulsion. The result is a pavement surface that has a rough texture and a very deep, rich black in color.

What?

A road overlay is typically done when a road surface has deteriorated but the underlying structure is still in relatively good condition. An overlay is adding another layer of asphalt on top of the existing pavement. 

Depending on the condition of the road, the removal and replacement of failed sections of the road are done prior to the overlay. This prep work is often referred to as "dig outs".

Depending on the condition of the road, Street Saver may recommend the the road surface be milled prior to the overlay. Milling is the use of a grinder to remove the existing pavement.

Depending on the condition of the road, Street Saver will recommend a thin overlay (1.5 inches in depth) or a thick overlay (2.5 inches in depth).

Why?

It's a cost-effective way to extend the life of a road without doing a full reconstruction. Here are the key conditions and timing for when an overlay is usually performed:

Common Signs/Reasons for a Road Overlay:

• Surface Distress: Cracks, rutting, minor potholes, or surface wear.
• Loss of Skid Resistance: The road becomes smooth and slippery.
• Oxidation or Weathering: Asphalt looks gray or brittle due to sun exposure and age.
• Ride Quality Degradation: Bumps or uneven surfaces cause poor driving comfort.
• Preventive Maintenance: Before major damage occurs, a thin overlay may be applied.
• Structural Evaluation: If inspections show the base layers are still strong, an overlay can be used instead of reconstruction.

Not Ideal When:

• There are major structural failures.
• The base/sub-base has significant water damage or instability.
• The pavement has severe rutting or large potholes that go deep.

When?

Should be done every 10–15 years, depending on traffic, weather, and original construction quality. Construction is done during the dry weather months.

How?

Once the road surface has been prepped, a paving machine is used to install the new asphalt.  This work is typically done by paving contractors hired by the County.

What?

Reconstructing the road involves removing the existing failed pavement and base rock using equipment such as a milling machine.

Why?

When a road has deteriorated to the point that the integrity of the existing roadbed won't support an overlay, reconstruction is necessary.  Adding an overlay on top of roadbed that has failed will cause the new pavement to fail soon after installation. 

When?

When the road surface has failed and has the appearance of an "alligators back", those portions of the road will need to be reconstructed.

How?

The existing road surface and base rock are removed and replaced.  In addition, the sub-base below the base rock is often strengthened. Sometimes, existing pavement is removed using a milling machine and the grindings from the milling process are recycled into the new pavement. This work is typically done by paving contractors hired by the County.