Bituminous Surface Treatment | Bituminous Surface Treatment Cost | Bituminous Pavement Failure

In this article, we will discuss

What is Bituminous Surface Treatments(BST) | Purpose of Bituminous Surface Treatments(BST) | Main Types of Bituminous Surface Treatments | Methods Used for Bituminous Surface Treatment | Bituminous Surface Treatment Cost

What is Bituminous Surface Treatments(BST)

A chip seal or seal coat is a bituminous surface treatment (BST). It's a surface treatment made of liquid asphalt and a thin layer of gravel that's about 0.5 inches thick or less. Most of the time, BSTs are used on sidewalks with less traffic.

All of the following can be done with BSTs:

• A waterproof layer on top of the pavement protects it.

• Increased resistance to slipping.

• Filler for surfaces that are already broken or torn.

• A surface that doesn't reflect light when it's wet and a surface that reflects more light at night.

Since the 1920s, BSTs have been used, mostly on gravel roads with low traffic. BSTs are being used more and more as a form of preventive maintenance on flexible pavements that have a good structure.

Purpose of Bituminous Surface Treatments(BST)

A BST protects the pavement structure from the sun and water, which can cause it to break down over time. BSTs add a new wearing course and a waterproof layer on top of the current pavement. A BST makes it harder for water to get into the base material. This stops damage from freezing and thawing in places where it gets below freezing.

Due to the cover aggregate, BSTs also make the surface of the pavement more slippery. This prevents ravelling, which can make the sidewalk slippery and make it hard to stop. A BST gives the surface of the pavement a good grip.

BSTs should be put on a pavement surface that has no or only mild cracks. Most things have a service life of two to four years, but some can last up to five years.

Main Types of Bituminous Surface Treatments

1. Single Surface Treatment

The bituminous surface is made by putting bitumen on a surface that has already been prepared once and then rolling the surface right away, preferably with a roller with pneumatic tires.

2. Multiple Surface Treatment

In this type of treatment, the bitumen is put down in two or three layers, with the size of the gravel getting smaller with each layer. Each layer is rolled right away, preferably with a roller with pneumatic tires.

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Main Materials

BSTs are made up of two main components: asphalt and a cover aggregate.

Essential Material of Bituminous Surface Treatments

1. Aggregate

i. Size

The ideal particle size distribution for aggregate used in a single surface treatment is between 1/2 and 14 inches (13 and 6 mm). The aggregate size for the first layer of a multi-surface treatment project should be between 1 and 1/2 inches (25 and 13 mm) in diameter, with the aggregate size decreasing by about 1/2 inch (13 mm) for each succeeding layer.

Aggregates of the larger size can be used in more than one type of therapy. Tire noise is a common complaint when driving on roads with aggregates larger than half an inch (13 mm).

ii. Shape

Cubes are the best shape for the aggregate. Aggregates that are flat or long are not good. Aggregates that are flat tend to line up on their flat sides, and bituminous materials may cover them completely. Rounded aggregates tend to roll and don't hold together well, so they are not good.

iii. Cleanliness

It is very important that the aggregate is clean. If the coarse aggregates are dusty or covered with small particles, the bitumen won't stick to them. This means the road won't work well and will lose cover aggregate. It is suggested that the weight of the aggregate that gets through the No. 200 mesh screen should not be more than 1%.

2. Bitumen

i. Asphalt Cement

The asphalt cement must be uniform and free of water. When heated to 347°F (175°C), it shouldn't foam. The asphalt cement must meet the requirements in the following table:

ii. Cutback Asphalt

When heated to the application temperature, the cutback asphalt shouldn't foam, and it should meet all of the requirements in the table.

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iii. Emulsified Asphalt

After mixing it well, the emulsified asphalt should be uniform, as long as it hasn't separated because of freezing. Asphalts that have been mixed and then separated by freezing should not be tested. The requirements for emulsified asphalt are listed in the table below:

The Methods Used for Bituminous Surface Treatment

• The road's surface will be fixed by patching the holes and filling the cracks.

• Clean the road surface that will be covered by the surface treatment with a rotary broom or another approved tool.

• Depending on the type and grade of the bituminous material, it is sprayed at a certain rate and temperature.

• The best range of viscosity for spraying is between 20 and 120 CST.

• The cover aggregate is spread at a certain rate right after the bituminous material is sprayed to get the deepest chip wetting possible.

• This is necessary because asphalt cement and road tar thicken quickly when they cool, but asphalt emulsions and cutback asphalts need this to make the most of the meniscus effect.

• Within 2 minutes of putting down the bituminous material, the cover aggregate should be put on top of it.

• To spread the aggregate, you should use a self-propelled mechanical spreader or another device that can evenly spread the aggregate at the specified rate and width.

• The spreader must be set up so that it puts down the amount of cover aggregate called for in the project's design specs.

• Right after putting down the cover aggregate, the surface is rolled to press the chips into the bituminous membrane. This is best done with a roller with pneumatic tires.

• The roller shouldn't go faster than 5 mph. A 12–15-ton pneumatic-tired roller is usually used three times, depending on the type and amount of bituminous material and the weather.

• After the bituminous material is put down, the aggregate should be rolled out within 5 minutes. The other three coverages should be done within 30 minutes.

• Slow down traffic until the asphalt has been put down. After the surface treatment is put down, traffic should not go faster than 20 mph for 4 hours.

• If you want to treat more than one surface, repeat steps 3 through 6.

• The next coats can only be put on after the previous bituminous surface has hardened and set, which usually takes a day.

Precautions for Bituminous Surface Treatment Construction

• Surface treatment jobs shouldn't be done when it's cold or wet outside or both. During the work, the surface should be clean and dry.

• Before starting the operation, the air temperature in the shade should be at least 50°F (10°C) and rising.

• When the temperature is 60°F or less and going down, the operation should not be allowed.

• The operation shouldn't be done when it's raining or when it looks like it might rain.

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Bituminous surface Treatment Cost

Otta Seal is a low-cost method of Bituminous Surface treatment

Otta Seal Method

Otta seal is a new, low-cost alternative to traditional bituminous surface treatment (BST) that has just been introduced in the United States.

Otta seals can last for a long time, but how long they last depend on a number of things, such as:

Type of Otta seal

• Average daily traffic (ADT)

• Quality of surfacing (aggregate strength, binder durability,

• construction quality, etc.)

Bituminous Pavement Failure and Surface Treatment

Pavement failure occurs when an asphalt surface no longer holds its original shape and develops material stress which causes issues. Pavement failure issues include cracking, potholes, depressions, rutting, shoving, upheavals, and ravelling.

Causes Pavement Failure

Pavement failure can be caused by a number of things, such as water getting in, stress from heavy vehicles, temperature changes that cause expansion and contraction, and exposure to the sun. It is important to do regular maintenance like sealing cracks and asphalt so that cracks don't get bigger or start to form.

Cracking 

Cracks in asphalt are by far the most common cause of pavement failure. This is because cracks tend to spread and there are many things that can cause cracks. It's pretty normal for an asphalt surface to crack over time because the soil settles and it's exposed to the weather. However, there are some less common but common cracking problems that can happen if the mix design for the pavement wasn't done right.

Alligator Cracking

Alligator cracking happens when the subgrade and asphalt base start to get smaller because of the weight of the vehicles on them. People often hear alligators cracking at intersections where cars have been stopped for a long time. The first cracks will appear and grow as the water gets in and the asphalt base is pressed down more.

Joint Cracking

When a flexible concrete base is paved over with asphalt, cracks form at the joints. Over time, the concrete sub-base will grow and shrink, which will cause cracks to form along the joints.

Edge Cracking

Edge cracking happens along the edge of a road and is usually caused by water damage, not enough base material, and a lot of traffic on the road.

Transverse Cracking

Transverse cracks run across an asphalt road and are caused by a base that settles or moves, a paver that isn't working right, or big changes in temperature.

Block Cracking

Block cracks are caused by changes in temperature from season to season, which make the asphalt expand and contract. Block cracking happens when an asphalt surface is made with a mix that is too rigid and doesn't give the surface enough room for seasonal changes in density.

Linear Cracking

Linear cracks run parallel to the road and are usually caused by pavement wear and tear, but they can also be caused by weak spots in a parking lot or joints in the road's pavement.

FAQS

What is surface treatment pavement?

Surface Treatment is the process of putting an asphalt emulsion on an asphalt road or a new, compacted granular surface, and then putting a cover aggregate on top of that.

What are the types of surface treatment?

There are 21 different processes that are considered to be common types of surface treatment.

1. Micro-arc Oxidation 2. Metal Wire-drawing 3. Bluing 4. Shot blasting 5. Sandblasting 6. Etching

Which bituminous material is most commonly used?

Bitumen that comes from nature is often used in buildings. Natural bitumen, also called "native asphalts," is a type of bitumen that has formed naturally over time because of the weather. It can be used without being refined by distillation, and its composition and properties are very different.