Roadside Management Toolbox: Asphalt Concrete (2023)

Roadside Management Toolbox: Asphalt Concrete (1)Roadside Management Toolbox: Asphalt Concrete (2)

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What is This Treatment?

Asphalt concrete (AC) is a standard Type B asphalt concrete mixed, spread and compacted as noted in the Caltrans standards. Base material (4 -8 inches) and AC depth (2 - 6 inches) will vary depending on site specific requirements.

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Where to Use This Treatment?

Asphalt concrete (AC) pavement is recommended for use as a roadside management strategy in medians, gore areas, and in narrow strips adjacent to sound walls and retaining walls. AC is most effective and context appropriate in urban and suburban areas where the roadside AC will be contiguous to the roadway. Asphalt concrete paving may be patterned and/or colored during installation (see Stamped Asphalt Concrete).

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  • AC paving is a commonly used road construction material and readily available in most locales.
  • Most contractors and Caltrans Maintenance crews have the equipment and construction knowledge for proper installation.


  • Because it is a rigid material, AC paving is not recommended to be placed within 8 inches of guard rail and sign posts. To control weed growth under guard railing, see Vegetation Control (Minor Concrete).
  • AC paving has a relatively low initial installation cost, but is not as cost effective as Minor Concrete when the full lifecycle cost is considered.
  • AC paving not regularly compacted by traffic will degrade faster than AC paving exposed to traffic. Degradation of paving may allow weeds to establish.
  • If the treatment area has restricted access or other limiting factors standard compaction with equipment may not be attainable.
  • Obtaining the correct AC mix for projects with small quantities of AC or night work requirements may prove problematic and expensive.
  • Excavation for base materials may require removal of ADL (Aerially Deposited Lead) and increase costs.


  • 2010 Standard Specification – 39-1.14 Miscellaneous Areas and Dikes
  • 2010 Standard Specification – 39-1.28 Roadside Paving
  • 2010 Standard Special Provision (SSP) 39-1.28 Roadside Paving
  • 2010 Standard Specification – 39-1.29 Soil Treatment
  • 2010 Standard Special Provision (SSP) 39-1.29 Soil Treatment
  • 2006 Standard Specification – 39-7.01 Miscellaneous Areas


  • $18 - $70/yd2 Variable depending on quantity, soil prep., base depth, AC depth and access.
  • BEES Item(s) - TBD

Updated May 24, 2015

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What should be considered when designing asphalt concrete? ›

An asphalt concrete mixture must be designed, produced and placed in order to obtain the following desirable mix properties: 1) Stability, 2) Durability, 3)Impermeability, 4)Workability, 5) Flexibility, 6) Fatigue Resistance, and 7) Skid Resistance.

What are the suggested thicknesses for an asphalt concrete surface parking area for heavy trucks on gravelly or sandy well drained soils? ›


Medium Use: 5" to 6" concrete - Driveways and parking areas for light to medium trucks plus occasional use by heavier trucks. Heavy Use: 7" or thicker concrete - Driveways and parking areas for heavier commercial and industrial trucks.

How long does asphalt last compared to concrete? ›

Overall, the difference between asphalt and concrete driveways is that asphalt is less durable than concrete. With proper maintenance, it can last 30 years. Alternatively, concrete provides a sturdy, long-lasting option and can last homeowners 50+ years with occasional repairs and degreasing.

What is the suggested pavement thickness for a full-depth asphalt concrete driveway? ›

Full-Depth asphalt pavements for residential driveways should be a minimum of 4 in. (10 cm) com- pacted thickness on a properly prepared subgrade (see SUBGRADE PREPARATION, below). This minimum is sufficient for many years of service (automobiles and an occasional truck) if the driveway is properly constructed.

What are three 3 fundamental external design parameters for the design of pavement? ›

When designing pavements (both mix design and structural design), there are three fundamental external design parameters to consider: the characteristics of the subgrade upon which the pavement is placed, the applied loads and the environment.

What are the main factors to be considered in designing concrete mix? ›

The various factors affecting the mix design are:
  • Compressive strength.
  • Workability.
  • Durability.
  • Maximum nominal size of aggregate.
  • Grading and type of aggregate.
  • Quality Control.

Is 1.5 inches of asphalt enough for a driveway? ›

Driveways need a minimum compacted thickness of 2 inches (50mm) of hot mix asphalt. each asphalt layer is typically about three quarters the thickness of loose hot asphalt mix.

How many inches thick should an asphalt driveway be? ›

A 4-inch thickness may be adequate, but 5 or even 6 inches of full-depth asphalt will assure you of a stronger, stable driveway under a wider range of climate and loads. As an option, some contractors use 6 to 8 inches of compacted aggregate, or gravel, as a base under 3 inches of asphalt pavement.

How thick should a concrete parking lot be? ›

Using traditional design methodologies, standard-duty concrete lots required 7-inch of concrete over a 6-in subbase. The newer standard specifies 5-inch of concrete with no subbase. Heavy-duty lots that were once designed with 8-inch of concrete over a 6-inch subbase now require 6-inch concrete over a 4-inch subbase.

Can you put asphalt over old concrete? ›

Well, the answer is yes! It is safe to pave asphalt over concrete. Concrete is a great base material because it is stable and allows for excellent compaction of the asphalt above. In fact, many miles of concrete roads are paved over with asphalt every year.

Should you pour concrete over asphalt? ›

Paving concrete over asphalt is a technique usually done to save cash in the short term. However, the concrete cracks or scrapes away in the long run because of poor adherence to the base. It costs more to pave concrete over asphalt in the long run instead of repairing the parking lots and driving ways with new layers.

Is it cheaper to do concrete or blacktop? ›

While concrete driveways are more expensive initially than asphalt ones, they're cheaper in the long run due to their lifespan. Concrete driveways require little upkeep and will last for years. Longer lifespan especially with proper maintenance.

Is 4 inches of concrete thick enough for a driveway? ›

As for thickness, non-reinforced pavement four inches thick is standard for passenger car driveways. For heavier vehicles, a thickness of five inches is recommended. To eliminate standing water, the driveway should be sloped towards the street a minimum of one percent, or 1/8 inch per foot, for proper drainage.

What is the best base for an asphalt parking lot? ›

The secret to having the best asphalt driveway is by having a solid base. Using quality crushed gravel as a base to your blacktop will surely give you the perfect driveway quality that will last for a very long time.

What is the best base for asphalt driveway? ›

Strong blacktop driveways are typically built using crushed angular gravel as a base. This gravel needs to be a minimum of 6 inches thick for light vehicle traffic such as cars and pickup trucks.

What are the 3 concrete pavement distress? ›

(i) Longitudinal, Transverse, and Diagonal Cracks

These types of cracks can indicate poor construction techniques or weak underlying pavement layers.

What are the four major components in such pavement? ›

A typical flexible pavement consists of four components: Soil subgrade, sub-base course, base course, and surface course respectively.

What are the 3 components of concrete? ›

Concrete is made up of three basic components: water, aggregate (rock, sand, or gravel) and Portland cement. Cement, usually in powder form, acts as a binding agent when mixed with water and aggregates.

What are the four basic requirements of the concrete mix ratio? ›

  • Economy. The primary reason for systematically determining mixture proportions is economy. ...
  • Strength. ...
  • Durability. ...
  • Placeability.
May 27, 2022

How far can you drop concrete without it segregation? ›

Detailed Solution. Explanation: As per clause 13.2 of IS 456: 2000, the maximum permissible free fall of concrete to avoid segregation may be taken as 1.5 m or 150 cm.

Do I need 3 or 4 inch of asphalt for driveway? ›

Residential driveways typically use 2 to 3 inches of asphalt with 3 being suitable for occasional large trucks or heavy equipment. Underneath the asphalt you should have 6 to 8 inches of granular base aggregate.

Should a driveway be 4 or 6 inches? ›

Residential Driveway: Standard Concrete Driveway Thickness

The minimum thickness for a residential concrete driveway is 4 inches. However, 5 or 6 inches is recommended if you live in an area with heavy traffic or large vehicles. For extra strength and durability, you can go up to 8 inches.

What happens if asphalt is too thick? ›

If asphalt is applied too thickly, it won't be properly compacted, and over time, that can lead to depressions where traffic is frequent.

How thick should asphalt be after compaction? ›

Compaction and Thickness—A general rule of thumb is 4 inches for driveways and 6 inches for car parking lots (after compaction). To ensure consistent asphalt thickness, the sub-grade must be fine-graded and compacted prior to placing the asphalt.

How long should asphalt cure before driving on it? ›

Wait at least 3 full days before allowing traffic on the new asphalt. Since asphalt needs time to harden and cure, usually 6-12 months, your parking lot or driveway will remain soft and pliable until then.

What is the best grade of asphalt? ›

The 60-70 grade is usually used only in pavements where traffic is very heavy such as principle city streets and very heavily trafficked rural highways. The second grade, 85-100, is by far the most widely used material for plant mixes and is suitable for most pavements.

Does a concrete parking pad need rebar? ›

Concrete surfaces that support large trucks, heavy machinery, or steady traffic need concrete rebar reinforcement. Any structural concrete, like walls in buildings, should definitely include rebar. But if you're pouring a concrete driveway as a place to park your family minivan, you might not need rebar.

What PSI should concrete be for a parking lot? ›

Pavement durability relies on a good surface layer, freeze-thaw resistance and overall strength. Generally, in freeze-thaw areas where deicing salts are used, 4000 psi should be the minimum compressive strength for a parking lot.

Is asphalt or concrete better for a parking lot? ›

Go with asphalt and save in more ways than one

If you have a residential or commercial parking lot to install and maintain, yes, concrete may be considered a durable option, but it's also far more costly up front and takes longer to lay down.

Will asphalt bond to concrete? ›

If the question is "CAN I lay asphalt over concrete?" then the answer is "Yes." This is absolutely possible if elevations allow for it, and we're happy to lay asphalt driveways over concrete if that's what you want. It's also the cheaper option since heavy equipment is required to dig up an existing concrete slab.

What do you put between concrete and asphalt? ›

The quickest way to remedy these gaps is to purchase a tar-like sealant and fill the gap as soon as possible.
  1. Dig out any loose material between the asphalt and concrete using a hand shovel and clear any loose debris. ...
  2. Fill the gap with gravel, leaving 4 inches from the hole surface for the cold patch sealant.

Can you pave straight over concrete? ›

You can easily dress up your pool, patios, outdoor entertainment areas and even the driveway by laying pavers over existing concrete.

Do you need an expansion joint between asphalt and concrete? ›

Without expansion joints, asphalt pavement and concrete pavement would be susceptible to cracking in extreme temperature changes. So if you see a crack in your pavement, there's likely an expansion joint nearby. And if you're paving a new driveway or sidewalk, be sure to include expansion joints every few feet.

Will quikrete stick to asphalt? ›

Quikrete 50 lb. Commercial Grade Permanent Blacktop Repair Patch is designed to repair potholes and cracks over 1 in. wide in asphalt pavements. Provides superior placement and bonding characteristics and produces a virtually permanent repair, even in cold, damp conditions.

How do you prepare asphalt for concrete? ›

The Complete 7-Step Process for Asphalt Pavement Installation
  1. Step 1: Demolition and Removal.
  2. Step 2: Grading and Sloping.
  3. Step 3: Prepare the Sub Base.
  4. Step 5: Binder and Surface Course.
  5. Step 6: Install New Asphalt Surface.
  6. Step 7: Butt Joints and Transitions.
  7. To Complete the Project: Final Roll.
May 11, 2020

What type of driveway lasts the longest? ›

Concrete, cobblestone, asphalt, brick, and interlocking pavers are the most durable driveway installation options available today. Apart from their lengthy lifespans, these materials also hold up well in any climate, require minimal maintenance, offer a smooth drive, and elevate your home's first impression.

What is the cheapest driveway to install? ›

Gravel is by far the cheapest driveway material and one of the longest-lasting materials with a lifespan of 100 years. It still needs regular maintenance and dust suppression.

What is the best type of driveway to have? ›

Concrete is the most popular driveway material, and for good reason. Durable and low-maintenance, you won't have to give much thought to a concrete driveway. It may not earn as many compliments as upscale alternatives, but concrete is a dependably solid choice with a mid-range price.

Do you need wire mesh for 4 inch slab? ›

Here, pouring a concrete slab 4 inches in thickness is fine. While you may choose to reinforce it with rebar, wire mesh should be sufficient.

Do you need rebar for 4 inch slab? ›

No, you do not need rebar for a 4-inch slab of concrete on grade. A 4-inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required. Rebar is recommended on concrete measuring 5 – 6 inches thick.

Do you need gravel under concrete driveway? ›

Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.

How thick should the asphalt be for a parking pad? ›

For full-depth, light-duty commercial parking lots, Murphy recommends 4.5 inches compacted thickness of hot mix asphalt on the subgrade. For full-depth, heavy-duty parking lots, he recommends 7.5 inches of hot mix asphalt on subgrade.

What do you put under asphalt? ›

Traditional Aggregate Asphalt

A bed of gravel 6 to 8 inches deep is usually installed underneath an asphalt driveway. If the asphalt is poured before the gravel settles, the driveway will crack and split as the stones beneath it settle and shift.

What roller is best for asphalt? ›

Double-drum rollers

Compact, powerful and efficient, twin drum rollers are great for road and asphalting projects. These rollers have a smoother finish and are often used for the final stages of road construction or when following an asphalt paving machine.

What is the best thickness for an asphalt driveway? ›

A 4-inch thickness may be adequate, but 5 or even 6 inches of full-depth asphalt will assure you of a stronger, stable driveway under a wider range of climate and loads. As an option, some contractors use 6 to 8 inches of compacted aggregate, or gravel, as a base under 3 inches of asphalt pavement.

What is the minimum thickness of asphalt for a driveway? ›

Driveways need a minimum compacted thickness of 2 inches (50mm) of hot mix asphalt. each asphalt layer is typically about three quarters the thickness of loose hot asphalt mix.

What grade of asphalt is used for driveways? ›

The 41A asphalt type is a smoother surface. It is durable, but with a finer rock and sand mixture. This is what most homeowners choose for their driveways.

What factors must be considered when designing an asphalt pavements thickness? ›

Pavement Thickness Design Factors
  • 1 Flexural Strength of Concrete.
  • 2 Subgrade and Subbase Support.
  • 3 Design Period.
  • 4 Traffic. 4.1 Projection. 4.2 Capacity. 4.3 ADTT. 4.4 Truck Directional Distribution. 4.5 Axle-Load Distribution.
  • 5 Load Safety Factors.
  • 6 References.
Jul 14, 2015

What objectives must the design of an asphalt pavement mix meet? ›

The objectives of paving with an asphalt mix are to get a smooth, quiet ride with good strength, stability, and durability; with no rutting, shoving, or flushing; and with no cracking or raveling.

What are the different factors that influence the design properties of asphalt? ›


What do you look for in a concrete mix design? ›

The water/cement ratio is the most important parameter of the concrete mix design; it governs the strength, durability, and workability of the concrete mix. Here, you will need to enter the required compressive strength and associated water/cement ratio.

What is the most important factor for road concreting? ›

The most important step in road construction is the preparation of its subbase. This 350-mm layer serves as the foundation of the road and is often the primary load-bearing part. That is why it is essential that the material used for this layer is of high quality.

What is the maximum lift thickness for asphalt? ›

Generally, lift thicknesses are limited to 6 or 8 inches. Proper placement becomes a problem in lifts thicker than 8 or 8 inches. For open-graded mixes, compaction is not an issue since it is intended that these types of mixes remain very open.

What is the maximum layer thickness for asphalt? ›

When static steel-wheeled rollers are used, the maximum lift thickness that can be properly compacted is 3 inches. When pneumatic or vibratory rollers are used, the maximum thickness of lift that can be compacted is almost unlimited. Generally, lift thicknesses are limited to 6 or 8 inches.

What are the three common HMA mix design procedures? ›

In order to meet the demands placed by the preceding desirable HMA properties, all mix design processes involve three basic steps:
  • Aggregate selection. ...
  • Asphalt binder selection. ...
  • Optimum asphalt binder content determination.

How do you design pavement thickness? ›

The authors suggest the following computation method for obtaining pavement thickness using Gray's formula: (1) carefully study the traffic mix likely to occur at a project site; (2) calculate the total load and radius of the contact area on the basis of the proportions of vehicle types; (3) add an extra impact factor ...

What happens if asphalt is not compacted enough? ›

Insufficient compaction can result in raveling of the pavement. This is when the asphalt mix begins to separate, and the aggregate components detach from the mix. This can result in a weakened pavement, which leads to premature distress of the pavement and overall reduced life expectancy.

What is the most important property of asphalt? ›

Asphalt Physical Properties

Typically, the most important physical properties are: Durability. Durability is a measure of how asphalt binder physical properties change with age (sometimes called age hardening). In general, as an asphalt binder ages, its viscosity increases and it becomes more stiff and brittle.

What are the 3 main constituents of asphalt? ›

Asphalt consists of compounds of hydrogen and carbon with minor proportions of nitrogen, sulfur, and oxygen.

What is a 1 2 3 mix for concrete? ›

Concrete is made from cement, sand, gravel and water.

In making concrete strong, these ingredients should usually be mixed in a ratio of 1:2:3:0.5 to achieve maximum strength. That is 1 part cement, 2 parts sand, 3 parts gravel, and 0.5 part water.

What is the best concrete mix for slab? ›

A concrete mix of 1 part cement : 2 parts sand : 4 parts coarse aggregate should be used for a concrete slab. Concrete must be placed within half an hour of mixing. Place your concrete into your formwork; work the concrete into awkward places and corners using a shovel or trowel.


1. Bonded Concrete Overlay of Asphalt—Urban Pavement Rehabilitation Solutions
(American Concrete Institute)
2. The Safety Edge — Your Angle for Reducing Roadway Departure Crashes
(Federal Highway Administration USDOTFHWA)
3. Safety Edge Webinar - Proven Safety Countermeasure for Roadway Departure Crashes
(Ohio LTAP Center)
4. Potholes: Causes, Cures and Prevention
5. Lake County Division of Transportation (LCDOT) Pavement Management Techniques
6. Automated Detection of Road Defects Webinar
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