Types of Asphalt Paving Mix
Asphalt is the most popular choice in pavement materials these days. According to the Federal Highway Administration, there are more than four million miles of public roads in the United States of which around one million are paved. Approximately 800,000 of those roads are paved with asphalt.
There are a number of asphalt types to choose from. The material that works best is determined by factors such as the scope of the job, the location the pavement will be in, the climate, the time of year the pavement is being laid, and what conditions it will be exposed to. Reputable highway paving companies can help you decide which material is best for you.
The National Asphalt Pavement Association, the specific types of asphalt pavement includes: Stone-Matrix Asphalt, Perpetual Pavement, Porous Pavement, Warm-Mix Asphalt, Quiet Pavement, and Thinlays.
In order to achieve the characteristics each of the types of pavements are expected to achieve, various types of asphalt paving mixes are used in the making of the pavement.
Pavement mix types are categorized as:
Open-Grade Friction Course (OGFC)
An open-graded friction course is a permeable, thin layer of asphalt that has a structure of uniform aggregate size. The mix contains very few fines, resulting in a porous product due to the chemical make up and the manner the few fines interact with the uniform aggregate. Open-grade friction course is also known as asphalt concrete (ACP or AC), blacktop, hot mix, bitumen, or asphalt.
This type of porous asphalt mix is appreciated for its ability to carry heavy loads and resist trucks without becoming deformed, thus requiring asphalt maintenance. The method has a stone-on-stone skeleton because the load is carried by the stone aggregate while the actual asphalt fulfills the job of keeping everything cemented in place.
Open graded friction course mixes can handle large amounts of heavy traffic. It provides good traction. It also absorbs the sound of tires rolling over the surface by a rate of 50%. Another advantage of OGFC is that it performs excellent during wet weather because it reduces splashes and spray from vehicles. It also reduces oncoming traffic glare during rainy conditions and enhances the visibility of pavement markings.
This type of asphalt paving mix has been used in the United States since the 1950s for the purpose of improving friction resistance. Due to variances in the formulations of the mix, the effectiveness of OGFC was controversial. By 1974, the Federal Highway Administration (FHWA) developed a paving mix procedure for open-graded friction and since then, reported results have been more favorable. Significant improvements have also been put into place where better binders and gradation are concerned.
There are some legitimate drawbacks to OGFC, even when it is mixed properly and is comprised of high-quality ingredients. The unit weight per yard of this paving mix is more expensive than the other mixes are. But, because it is lighter and covers more area, the price balances out.
Raveling and delamination are other causes of concerns with OGFC. The open gradation of this type of mix creates pores, or small holes, in the pavement which is necessary for it to perform the function intended for it. The problem is that anything that clings to the pores, like slow moving traffic or excessive dirt on the road, can degrade the performance since it is designed to support fast movement.
Stone Matrix Asphalt (SMA)
Stone matrix asphalt, or stone mastic asphalt, was developed in the 1960s in Germany for the purpose of paving heavily trafficked roads with a durable material. This type of asphalt mix is designed to be a rut-resistant wearing course which is achieved by using a gap-graded aggregate structure plus a modified asphalt binder in the formulation. Ever since 1990, SMA has been used in the United States.
The use of stone-in-stone skeleton that is held together with a rich mix of asphalt-based cement coupled with stable agents like asphalt modifiers and/or fibers make this type of paving mix ideal for use on high-volume interstates where strength is vital. The aggregates are all in contact so the rut resistance feature relies on aggregate properties rather than on the binding material properties. Aggregates don’t deform near to the extent that asphalt binder do when placed under loads, so this stone-on-stone contact mix is very effective in reducing rutting.
In addition to interstates and heavy traffic areas, this type of mix is also used on race tracks, airport runways, and even on residential streets. SMA is one of the best noise absorbing pavement types. Typically, it is used as a surface course but occasionally, it serves as an intermediate course and for asphalt repair or a thin overlay.
It tends to run about 20% to 25% more than typical dense-grade mixes but it is cost-effective when it’s used in the right situation since it is durable and rut-resistant, like in locations where the climate is often snowy and icy and studded tires are used. Other types of pavements would require lots of maintenance when exposed to such rutting.
Open-Grade Mix
Open-grade mix paving is designed to be water permeable, unline dense-graded mixes and SMA. This type of mix uses crushed stone or gravel and a very small percent of manufactured sands. Open-grade friction course (OGFC) is a type of open-grade mix as is asphalt treated permeable bases (ATPB). There are less stringent specifications ruling asphalt treated permeable bases than open-graed friction course mixes. ATPB is only used under dense-graded HMA, SMA, or Portland cement concrete for purposes of drainage. For OGFC, however, a minimum of 15% air voids are allowed but no maximum air voids are set.
Dense-Grade Mix
The density of the mix makes a huge difference on how the asphalt is used and what it is used for. There are two main types of dense-grade mix including fine-grade and coarse-grade.
Fine-Grade Dense Mix
Fine-grade dense mix paving asphalt are comprised of more sand-sized and fine particles than coarse-grade mixes are. Fine-grade mixes are typically used where light traffic abounds. It is also used for penetration macadam which is a crushed stone aggregate or screened gravel that is bound by bituminous grout, the introduction of the binder being after the aggregate is compacted.
Coarse-Grade Dense Mix
As the name implies, course-grade dense mix asphalt paving mixes contain more coarse-grade material than they do fine-grade. It is typically used as a binding agent or base coarse for the purpose of providing support. Coarse-grade mixture is frequently used to provide a surface lift for parking lots, drive ways, and roads because it is not only serviceable, it has eye appeal as well.
There are a number of asphalt types to choose from. The material that works best is determined by factors such as the scope of the job, the location the pavement will be in, the climate, the time of year the pavement is being laid, and what conditions it will be exposed to. Reputable highway paving companies can help you decide which material is best for you.
The National Asphalt Pavement Association, the specific types of asphalt pavement includes: Stone-Matrix Asphalt, Perpetual Pavement, Porous Pavement, Warm-Mix Asphalt, Quiet Pavement, and Thinlays.
In order to achieve the characteristics each of the types of pavements are expected to achieve, various types of asphalt paving mixes are used in the making of the pavement.
Pavement mix types are categorized as:
Open-Grade Friction Course (OGFC)
An open-graded friction course is a permeable, thin layer of asphalt that has a structure of uniform aggregate size. The mix contains very few fines, resulting in a porous product due to the chemical make up and the manner the few fines interact with the uniform aggregate. Open-grade friction course is also known as asphalt concrete (ACP or AC), blacktop, hot mix, bitumen, or asphalt.
This type of porous asphalt mix is appreciated for its ability to carry heavy loads and resist trucks without becoming deformed, thus requiring asphalt maintenance. The method has a stone-on-stone skeleton because the load is carried by the stone aggregate while the actual asphalt fulfills the job of keeping everything cemented in place.
Open graded friction course mixes can handle large amounts of heavy traffic. It provides good traction. It also absorbs the sound of tires rolling over the surface by a rate of 50%. Another advantage of OGFC is that it performs excellent during wet weather because it reduces splashes and spray from vehicles. It also reduces oncoming traffic glare during rainy conditions and enhances the visibility of pavement markings.
This type of asphalt paving mix has been used in the United States since the 1950s for the purpose of improving friction resistance. Due to variances in the formulations of the mix, the effectiveness of OGFC was controversial. By 1974, the Federal Highway Administration (FHWA) developed a paving mix procedure for open-graded friction and since then, reported results have been more favorable. Significant improvements have also been put into place where better binders and gradation are concerned.
There are some legitimate drawbacks to OGFC, even when it is mixed properly and is comprised of high-quality ingredients. The unit weight per yard of this paving mix is more expensive than the other mixes are. But, because it is lighter and covers more area, the price balances out.
Raveling and delamination are other causes of concerns with OGFC. The open gradation of this type of mix creates pores, or small holes, in the pavement which is necessary for it to perform the function intended for it. The problem is that anything that clings to the pores, like slow moving traffic or excessive dirt on the road, can degrade the performance since it is designed to support fast movement.
Stone Matrix Asphalt (SMA)
Stone matrix asphalt, or stone mastic asphalt, was developed in the 1960s in Germany for the purpose of paving heavily trafficked roads with a durable material. This type of asphalt mix is designed to be a rut-resistant wearing course which is achieved by using a gap-graded aggregate structure plus a modified asphalt binder in the formulation. Ever since 1990, SMA has been used in the United States.
The use of stone-in-stone skeleton that is held together with a rich mix of asphalt-based cement coupled with stable agents like asphalt modifiers and/or fibers make this type of paving mix ideal for use on high-volume interstates where strength is vital. The aggregates are all in contact so the rut resistance feature relies on aggregate properties rather than on the binding material properties. Aggregates don’t deform near to the extent that asphalt binder do when placed under loads, so this stone-on-stone contact mix is very effective in reducing rutting.
In addition to interstates and heavy traffic areas, this type of mix is also used on race tracks, airport runways, and even on residential streets. SMA is one of the best noise absorbing pavement types. Typically, it is used as a surface course but occasionally, it serves as an intermediate course and for asphalt repair or a thin overlay.
It tends to run about 20% to 25% more than typical dense-grade mixes but it is cost-effective when it’s used in the right situation since it is durable and rut-resistant, like in locations where the climate is often snowy and icy and studded tires are used. Other types of pavements would require lots of maintenance when exposed to such rutting.
Open-Grade Mix
Open-grade mix paving is designed to be water permeable, unline dense-graded mixes and SMA. This type of mix uses crushed stone or gravel and a very small percent of manufactured sands. Open-grade friction course (OGFC) is a type of open-grade mix as is asphalt treated permeable bases (ATPB). There are less stringent specifications ruling asphalt treated permeable bases than open-graed friction course mixes. ATPB is only used under dense-graded HMA, SMA, or Portland cement concrete for purposes of drainage. For OGFC, however, a minimum of 15% air voids are allowed but no maximum air voids are set.
Dense-Grade Mix
The density of the mix makes a huge difference on how the asphalt is used and what it is used for. There are two main types of dense-grade mix including fine-grade and coarse-grade.
Fine-Grade Dense Mix
Fine-grade dense mix paving asphalt are comprised of more sand-sized and fine particles than coarse-grade mixes are. Fine-grade mixes are typically used where light traffic abounds. It is also used for penetration macadam which is a crushed stone aggregate or screened gravel that is bound by bituminous grout, the introduction of the binder being after the aggregate is compacted.
Coarse-Grade Dense Mix
As the name implies, course-grade dense mix asphalt paving mixes contain more coarse-grade material than they do fine-grade. It is typically used as a binding agent or base coarse for the purpose of providing support. Coarse-grade mixture is frequently used to provide a surface lift for parking lots, drive ways, and roads because it is not only serviceable, it has eye appeal as well.
Asphalt Pavement Mix Classifications
Types of asphalt pavement mixes fall into classifications that distinguish the characteristics of the mix. The most common classifications are:
Cold Mix Asphalt
Cold mix asphalt (CMA) is a type of mix that stays soft when exposed to cold temperatures which is especially useful when asphalt a pavement company is required to do the work during the winter months in cold climate locations. The process for manufacturing this mix is relatively simple so it can be created at almost any temperature, no matter how hot or cold the weather is. Cold mix is conducive for repelling water too so it is often employed for pothole repairs.
Hot Mix Asphalt
Hot mix asphalt (HMA) defines asphalt mixes that require heating and pouring at temperatures between 300 to 350 degrees. HMA is the most widely used asphalt in existence.
There are three categories of hot mix asphalt - open grade mixes, dense-graded mixes, and stone matrix asphalt. Dense-grade mixes are known by the size of the aggregate that is used to make them.
All three types of hot mix asphalt are widely used on highways, interstates, and high traffic roadways.
Warm Mix Asphalt
Warm mix asphalt (WMA) is a mix that is manufactured at a temperature that is between 200 and 250 degrees. When producing this type of mix, less fossil fuel is used that with hot mix asphalt. It requires more binding materials, however, so that it is able to be poured and spread at the lower temperature. It is used when possible because it is less expensive than hot mix asphalt.
Coarse-Graded Asphalt
Coarse-graded asphalt, also referred to as dense-grade asphalt, is comprised of coarse aggregate, for the most part. It is used where traction is of essence, like where snow and ice are found. This type of mix is great for all traffic conditions and all layers of the pavement. It is excellent for leveling and patching when repairing asphalt and is a works well as a structural mode. It is frequently used where traction is of essence, like where snow and ice are found.
Cold Mix Asphalt
Cold mix asphalt (CMA) is a type of mix that stays soft when exposed to cold temperatures which is especially useful when asphalt a pavement company is required to do the work during the winter months in cold climate locations. The process for manufacturing this mix is relatively simple so it can be created at almost any temperature, no matter how hot or cold the weather is. Cold mix is conducive for repelling water too so it is often employed for pothole repairs.
Hot Mix Asphalt
Hot mix asphalt (HMA) defines asphalt mixes that require heating and pouring at temperatures between 300 to 350 degrees. HMA is the most widely used asphalt in existence.
There are three categories of hot mix asphalt - open grade mixes, dense-graded mixes, and stone matrix asphalt. Dense-grade mixes are known by the size of the aggregate that is used to make them.
All three types of hot mix asphalt are widely used on highways, interstates, and high traffic roadways.
Warm Mix Asphalt
Warm mix asphalt (WMA) is a mix that is manufactured at a temperature that is between 200 and 250 degrees. When producing this type of mix, less fossil fuel is used that with hot mix asphalt. It requires more binding materials, however, so that it is able to be poured and spread at the lower temperature. It is used when possible because it is less expensive than hot mix asphalt.
Coarse-Graded Asphalt
Coarse-graded asphalt, also referred to as dense-grade asphalt, is comprised of coarse aggregate, for the most part. It is used where traction is of essence, like where snow and ice are found. This type of mix is great for all traffic conditions and all layers of the pavement. It is excellent for leveling and patching when repairing asphalt and is a works well as a structural mode. It is frequently used where traction is of essence, like where snow and ice are found.
Where Asphalt Paving is Used?
Asphalt pavement is not only found on most of the paved roads in America, it is also used in many other places, like on busy commercial airport runways such as the ones in Oakland, Baltimore-Washington, and Las Vegas.
Out of the thirty-three national NASCAR race tracks in the US, thirty-one of them are paved with asphalt. Sixty-six of NASCAR Short Track series race tracks are asphalt.
Asphalt is also used to pave parking lots and business and residential driveways. It’s clear to see that asphalt is highly favored over other traditional paving materials, like concrete and paver stones.
Out of the thirty-three national NASCAR race tracks in the US, thirty-one of them are paved with asphalt. Sixty-six of NASCAR Short Track series race tracks are asphalt.
Asphalt is also used to pave parking lots and business and residential driveways. It’s clear to see that asphalt is highly favored over other traditional paving materials, like concrete and paver stones.
Why Asphalt Pavement is PreferreD
There are some definite advantages when it comes to using asphalt versus other types of pavement. Here are some of the big benefits of asphalt:
Eco-friendly
Asphalt is the most recycled material in the entire world. Asphalt milling companies use a machine, called an asphalt milling machine, to collect and recycle pavement surfaces that are being repaved. Asphalt repair and maintenance crews then use the recycled material to patch, fill, and pave roads, parking lots, and drive ways. Recycled asphalt is used at an astounding rate of 99%. The majority of all new paving jobs as well as asphalt parking lot repair and road repair are mostly completed with recycled asphalt.
Cost
Asphalt is very economical. It is made using petroleum which is easy to attain and as long as petroleum prices are somewhat stable, is a lot cheaper than concrete. Even when petroleum prices are up, the fact that asphalt is recycled makes it less expensive per unit weight of asphalt. Asphalt repair and maintenance is more affordable than any other type of pavement. The time and labor it takes to complete asphalt related construction projects are budget-friendly too.
Safety
Asphalt is considered to be safer than concrete for several reasons. The fact that different types of asphalt paving mixes are available mean surfaces can be specialized for their needs. For instance, highways in areas where rainy weather is common can elect to pave with a porous asphalt mix, like an open-graded friction course.
Quiet
In congested traffic areas, like Los Angeles, noise pollution is a huge problem. Asphalt is quieter to drive on than concrete. Flexible pavement is made out of bituminous materials that actually absorb noise.
Adaptable
Asphalt is more weather resistant than other pavement options. It can be designed to suit all climates and all traffic conditions, from high to low. Because there are a variety of asphalt paving mixes available and a number of application techniques to choose from, there truly is an asphalt product to meet most any pavement requirement.
Eco-friendly
Asphalt is the most recycled material in the entire world. Asphalt milling companies use a machine, called an asphalt milling machine, to collect and recycle pavement surfaces that are being repaved. Asphalt repair and maintenance crews then use the recycled material to patch, fill, and pave roads, parking lots, and drive ways. Recycled asphalt is used at an astounding rate of 99%. The majority of all new paving jobs as well as asphalt parking lot repair and road repair are mostly completed with recycled asphalt.
Cost
Asphalt is very economical. It is made using petroleum which is easy to attain and as long as petroleum prices are somewhat stable, is a lot cheaper than concrete. Even when petroleum prices are up, the fact that asphalt is recycled makes it less expensive per unit weight of asphalt. Asphalt repair and maintenance is more affordable than any other type of pavement. The time and labor it takes to complete asphalt related construction projects are budget-friendly too.
Safety
Asphalt is considered to be safer than concrete for several reasons. The fact that different types of asphalt paving mixes are available mean surfaces can be specialized for their needs. For instance, highways in areas where rainy weather is common can elect to pave with a porous asphalt mix, like an open-graded friction course.
Quiet
In congested traffic areas, like Los Angeles, noise pollution is a huge problem. Asphalt is quieter to drive on than concrete. Flexible pavement is made out of bituminous materials that actually absorb noise.
Adaptable
Asphalt is more weather resistant than other pavement options. It can be designed to suit all climates and all traffic conditions, from high to low. Because there are a variety of asphalt paving mixes available and a number of application techniques to choose from, there truly is an asphalt product to meet most any pavement requirement.
Asphalt serves a myriad of needs from acting as a structure to support heavy traffic weighing tons to providing smooth, beautiful surfaces to walk on, drive on, and even to play on. They type of asphalt that is chosen should reflect the needs and desires of the area it is to cover. Fortunately, when it comes down to it, the choices are practically limitless.
