The Benefits and Drawbacks of Chip Seal Roads

Chip seal, also known as tar-and-chip or sealcoating, is a popular paving method used on roads, driveways, and parking lots. It involves spraying a layer of hot asphalt oil onto an existing pavement surface, then immediately covering it with a layer of small crushed rock chips. The chips are then compacted into the asphalt using a roller. When done properly, chip seal forms a durable, waterproof surface that can extend the life of aging asphalt at a fraction of the cost of traditional repaving.

However, chip seal also has some downsides. The rough surface texture and loose rocks can increase tire wear and noise pollution. And without proper maintenance, chip seal can deteriorate more quickly than other paving solutions. Understanding both the pros and cons of chip seal can help you determine if it's the right solution for your paving project.

Advantages of Chip Seal

There are several reasons chip seal is a popular pavement preservation technique on low-volume roads and driveways:

• Cost-effective - Chip seal typically costs $2-$3 per square foot, compared to $7-$13 per square foot for conventional asphalt repaving. It provides a new wearing surface at a fraction of the cost.
• Quick installation - Chip seal can be installed and opened to traffic in as little as 24-48 hours. Other paving methods require days or weeks of curing time.
• Seals and protects - The asphalt binder seals cracks and raveling, preventing water intrusion that can damage the pavement structure.
• Adds pavement structure - The aggregate layer adds thickness and structure to the existing pavement.
• Provides good traction - Angular aggregate chips create an excellent skid-resistant wearing surface.
• Extends pavement life - A properly maintained chip seal can extend the service life of aging asphalt by 7-10 years.

The low cost and fast application make chip sealing ideal for lower-volume county roads, driveways, parking lots, and urban streets. The waterproof membrane protects the underlying pavement from deterioration while restoring traction and a smooth surface.

Cost Savings

One major advantage of chip seals is the lower cost compared to hot-mix asphalt paving or concrete. Materials and installation for chip seal typically run $2-$3 per square foot, whereas asphalt repaving often costs $6-$13 per square foot. The material costs for chip seal are 50-85% lower than other pavements.

Chip sealing is also fast and efficient - road crews can complete up to 10 lane-miles per day with minimal traffic delays. The rapid installation reduces labor, fuel, and traffic control costs compared to traditional paving. All of these factors make chip seal a budget-friendly preservation technique for aging roads and driveways.

Protection from Weathering

Applying a fresh layer of asphalt binder and aggregate chips serves to protect the underlying pavement structure. The asphalt seals cracks and prevents water intrusion that can cause damage from freeze-thaw cycles. Water trapped below the surface causes issues like potholes, raveling, and base failures.

The new chip seal waterproofs the surface, keeping the base and subgrade intact. This protects the integrity of the roadway while also providing a new driving surface. Preventing water damage can extend the lifespan of aging pavement significantly.

Quick Installation

A major benefit of chip seals is the ability to open them quickly to traffic - usually within 24-48 hours after installation. The asphalt cures rapidly, allowing the roadway to be used without extended lane closures or work zone restrictions.

The quick installation is ideal for preserving rural roads, driveways, and parking lots where closure time needs to be minimized. Other paving options like asphalt overlays can require days or weeks until the material has properly cured and stabilized.

Disadvantages of Chip Seal

For all its benefits, chip seal also comes with some potential drawbacks. Being aware of these downsides can help determine if it's the right solution for your project:

• Rough surface - Loose chips create a rough, noisy surface that can increase tire wear.
• Chip loss - Traffic dislodges loose chips, leaving pockets of missing aggregate.
• Short term life - Chip seals typically last 5-7 years before requiring maintenance.
• Frequent reapplication - Maintaining chip seals requires reapplying a sealcoat every 3-5 years.
• Not for high traffic - Chip seal performs best on low-volume roads and driveways.
• Timer and labor intensive - Proper installation is crew-intensive with specific temperature requirements.
• Need to sweep - Excess loose chips must be swept after installation to prevent windshield damage.

While chip seal provides an inexpensive, short-term solution, it requires more frequent maintenance to retain those benefits long-term. It also creates a rough, noisy surface not ideal for high-traffic areas. Being aware of these potential drawbacks allows for proper planning and use on appropriate projects.

Rough, Noisy Surface

One frequent complaint about chip seals is the coarse, rocky surface texture. The loose aggregate chips create rumble and road noise when driven over. This can lead to noise pollution near residential areas. The rough surface also increases tire wear and decreases ride quality compared to smooth asphalt.

However, the rough surface does benefit traction and skid resistance in wet weather. Over time, traffic wear helps embed the chips into the asphalt for a smoother drive. But chip seal remains a visibly coarse surface even after it cures.

Chip Loss

Excess aggregate chips that are not properly set into the asphalt tend to become dislodged by traffic. This leaves pockets of missing aggregate and exposes the underlying pavement. Chip loss occurs most frequently on curves, hills, intersections and high-traffic areas.

Sweeping loose chips after installation helps prevent this problem. Chip loss can also indicate inadequate asphalt binder or poorembedment during rolling. Fixing chip loss areas requires patching or re-applying a sealcoat to maintain the surface.

Frequent Reapplication

One downside of chip seals is the need for frequent maintenance to keep the surface intact. Traffic wear, weathering, and UV exposure cause the asphalt binder to become brittle and degrade within 2-5 years. At this point, a new chip seal or sealcoat needs to be applied.

Most agencies plan for resealing chip seal roads every 3-5 years to maintain performance. This reapplication schedule keeps costs lower than a full rebuild but requires more frequent work compared to longer-lasting pavements.

How Chip Seals Work

Understanding what happens during a chip seal installation helps clarify why the process works well in certain applications. The basic installation steps include:

1. Clean and prepare surface - Clear dirt, debris and sweep thoroughly so the asphalt adheres properly.
2. Spray binder - Apply a uniform layer of hot liquid asphalt over the surface using a distributor truck.
3. Spread aggregate - Immediately spread a uniform layer of chip rock into the asphalt using a chip spreader.
4. Embed chips - Use pneumatic rollers to embed the chips into the asphalt binder while its hot.
5. Sweep away excess - Remove any loose chips to prevent flying debris after the roadway opens.

The hot asphalt binder acts as an adhesive to hold the aggregate chips in place as a protective wearing course. The angular stones also provide macrotexture for excellent skid resistance. The process waterproofs the surface while adding thickness and structure to the pavement.

Asphalt Emulsion Options

Traditional hot applied chip seals use asphalt cement, a petroleum-based binder. However, agencies are increasingly using asphalt emulsions consisting of asphalt particles suspended in water.

Asphalt emulsions provide better adhesion, more control during application, and faster breaking and curing. They allow chip seal application at a wider temperature range. Emulsified asphalts also reduce fumes during paving.

Aggregates

The aggregate used for chip seals is typically 3/8 or 1/2 inch crushed angular stone. The fractured faces provide optimal adhesion with the binder. Hard, durable aggregates like granite resist crushing and embed firmly into the asphalt.

Softer aggregates like limestone may polish and become dislodged. Using quality, properly graded aggregates is key to chip seal success and longevity.

Ideal Uses for Chip Seal

While chip seal has some drawbacks, it excels in certain applications where a rough but durable surface provides benefits. Some of the best uses for chip seal include:

• Low-volume rural roads - Durable yet inexpensive surface for farm roads, rural lanes.
• Driveways and parking lots - Longer life than slurry seals on private surfaces with slow-moving vehicles.
• Road maintenance - Quickly seals cracks, restores traction, and protects pavement.
• Shoulders and bike lanes - Adds shoulder structure and skid resistance in high-wear areas.
• Trails and pathways - Low-cost surfacing for walking trails and recreational paths.

Careful project selection focuses chip sealing in lower-speed areas where roughness and noise are less of an issue. The low cost and quick installation benefit rural agencies maintaining miles of aging roads.

Rural Roads

Low-volume rural roads see slower traffic speeds and turning movements that help chips adhere properly. Farm roads and rural lanes may only see a few hundred vehicles per day, meaning less aggregate loss.

The low cost of chip sealing fits budget constraints for rural counties trying to maintain extensive road networks. And the quick installation minimizes disruption to rural travel and agriculture operations.

Driveways

Many homeowners choose chip sealing over more expensive asphalt or concrete for paving long driveways. The cost savings are substantial for these long private surfaces.

Driveways also benefit from slower vehicle speeds that allow chips to adhere and embed. Hot turning tires help seat the stones firmly into the asphalt binder applied by the contractor.

Parking Lots

Commercial parking lots see mostly low-speed maneuvering. This makes them another good fit for chip sealing compared to major highways. Angled parking spots also reduce chip dislodgment that can occur with high-speed turns.

Businesses appreciate the low cost for refreshing aging parking surfaces. And the rapid installation means minimal disruption to customers and operations.

Key Considerations for Chip Seals

While chip seal succeeds on many projects, it's important to weigh several factors to ensure you choose the right paving method. Some key considerations include:

• Traffic - Chip seal works best on roads under 500 vehicles per day.
• Condition of existing surface - Fix major distresses before applying chip seal.
• Weather - Ideal chip seal temperature range is 60-140degF.
• Noise impacts - Chip seal increases noise levels near homes and businesses.
• User costs - Rough surface can increase tire wear and damage paint.
• Crew experience - Proper installation by an experienced chip seal crew is essential.

Evaluating these factors ensures you apply chip seal on appropriate projects where it will provide maximum benefit and longevity.

Traffic Volume and Speed

Higher vehicle speeds increase churning that can dislodge aggregate chips. Most agencies recommend chip seals only on roads below 500 vehicles per day. Major highways see too much traffic volume and high speeds that quickly wear away the surface.

However, chip seals can succeed on urban streets with moderate traffic if speeds are slower. Lower speeds allow chips to embed and adhere to the asphalt binder.

Condition of Existing Pavement

Chip seals function as a surface treatment, not a repair for pavement defects. Any major cracks, distortion or base failures should be addressed with patching and repairs prior to application.

It's also ideal for the existing pavement surface to be smooth with minimal roughness. This allows the chip seal to adhere evenly across the surface and form an effective seal.

Climate Considerations

Chip sealing relies on hot asphalt binder to properly embed the aggregate chips. Agencies prefer applying chip seals when pavement temperatures are between 60-140degF. Cooler weather can impede the asphalt from adhering and curing.

The climate also impacts chip seal performance. Freezing winters can cause seal deterioration through freeze-thaw cycles. And excess heat causes the asphalt to become too soft and wear quickly.

Tips for Longer Chip Seal Life

When applied correctly, chip seals provide excellent value by extending pavement life at low cost. Here are some tips for getting the longest life from your chip seal project:

• Sweep thoroughly before installation so the asphalt adheres to the pavement, not debris.
• Apply chip seal during ideal temperature range of 60-140degF.
• Use quality aggregates that resist crushing and polishing from traffic.
• Adequately heat and apply the asphalt at the right rate to fully coat stones.
• Roll chips thoroughly to embed aggregate into the asphalt.
• Sweep away excess loose chips within 48 hours of installation.
• Limit traffic speeds for at least 5 days after construction.
• Sealcoat every 3-5 years to waterproof the surface and fill voids.

Proper construction and maintenance practices will gain the maximum benefit from chip sealing your road, driveway or parking lot.

Sweeping Loose Aggregate

One key maintenance activity is sweeping loose stones that did not adhere to the asphalt. If left on the roadway, these chips quickly become dislodged by traffic.

Agencies use broom sweepers to remove the excess aggregate within 24-48 hours after construction. This prevents windshield damage and improves traction and ride quality.

Sealcoating

Applying a new sealcoat layer every 3-5 years helps preserve the chip seal surface. The added asphalt fill voids and re-bonds loose aggregate. Sealcoating maintains waterproofing and extends the longevity of the chip seal.

Timely maintenance sealcoating touches up fatigue and raveling to keep good performance. This avoids more costly repairs if the surface fails completely.

Alternatives to Chip Sealing

Beyond chip sealing, several other pavement options exist. Comparing pros and cons helps select the right surface treatment for specific projects:

• Asphalt overlay - Hot mix asphalt provides a very smooth, quiet, longer-lasting surface.
• Concrete - More expensive initially but holds up for 30+ years with minimal maintenance.
• Gravel roads - Inexpensive but higher loose stone and dust issues.
• Tar and chip - Similar to chip seal but uses a tar binder that can soften in heat.
• Double chip seal - Adds a second layer of chips for a thicker surface.

In some cases, the higher cost of alternatives like asphalt repaving or concrete may justify the added longevity and performance. Evaluating all options for your specific traffic, budget and needs is recommended.

Asphalt Overlays

Milling off old pavement and replacing with a few inches of new hot mix asphalt creates an exceptionally smooth, quiet surface. It also lasts 15-20 years with good preventive maintenance.

Asphalt overlays are typically best for high-volume roads where ride quality and low noise are priorities. They withstand heavy traffic much better long-term.

Concrete

Concrete pavement provides unmatched longevity, lasting 30 years or longer. The rigid surface resists rutting and deformation from heavy loads. Initial cost is higher, but concrete needs minimal maintenance.

Concrete works on interstate highways, busy urban streets, and industrial sites. The strength and durability justify the investment on critical infrastructure.