Bitumen Emulsion for Chip Seal
Bitumen Emulsion for Chip Seal provides a cost-effective solution to enhance road durability by protecting the surface and improving aggregate retention. With time, the asphalt surface of roads can deteriorate through erosion, raveling, loss of aggregate, honeycombing, and damage from sulphate attacks under various weather conditions such as frost, sunlight, heat, and road salting. Furthermore, snow removal, overloading, and friction-mostly from chains on tires and snowplow blades-can hasten this deterioration. If these damages are not treated in time with repairs and asphalt overlays, they can reach such a stage that the complete road surface and its layers get destroyed. Protective layers are highly recommended to prevent further deterioration. Not only do protective layers maintain the existing conditions, but they also reduce the immediate need to install overlays, fill cracks, and minimize wear of asphalt.
These preservation surface layers also provide waterproofing that protects the asphalt and layers underneath from further deterioration. It is a cost-effective measure for maintaining the road surface to keep it continuously operational and safe. Depending on the severity of distresses, volume of traffic, and type of asphalt, the method applied will be different. Several of these cost-effective techniques can be implemented either early on, or even before, the asphalt pavement has shown distress.
A Chip Seal is an application of asphalt emulsion on an existing road surface, followed by an application of aggregate chips. The surface is then rolled to embed the aggregate chips into the emulsion. Our Chip Seal emulsions are specifically formulated to perform in a variety of project conditions. We take the standard Chip Seal Oil and, by incorporating polymer and rejuvenating agents, enhance workability and improve retention of aggregate chips.
For roads with an average day-to-day trafficked volume of about 300 vehicles, this is where it becomes appropriate. Application of additional layer to the Chip Sealing such as asphalt overlays or one or two Slurry Seal layers or a single or double micro-surfacing layer will provide better durability performance in the more busy roads and high-traffic streets.
Terminology
Terminology Much of the terminology shown below associated with chip seals has been documented by ASTM or has been developed by the AASHTO Emulsion Task Forces (ETF). Common terms are included below:
Chip Seal : The application of an emulsified asphalt to a roadway surface followed by a single layer of aggregate. When more than one layer of emulsified asphalt and aggregate is applied, the terms double or triple chip seal are often used.
Surface Treatment, Surface Seal, Surface Dressing : These terms may be used as alternatives to chip seal when aggregates are applied to the emulsified asphalt.
CRS-2 : a cationic rapid setting emulsified asphalt.
RS-2 : an anionic rapid setting emulsified asphalt.
CRS-2P polymer modified : a cationic rapid setting emulsified asphalt typically modified with styrene-butadiene, a styrene-butadiene-styrene block copolymer or latex rubber.
RS-2P polymer modified : anionic rapid setting emulsified asphalt typically modified with styrene-butadiene, styrene-butadiene styrene block copolymer, or latex rubber.
HFRS-2P : an anionic rapid setting high-float emulsified asphalt typically modified with styrene-butadiene, a styrene-butadiene-styrene block copolymer or latex rubber.
CSS-1h : a cationic slow setting emulsified asphalt that normally used for fog seals. This contains a harder base asphalt than CSS-1.
CRS-1h : a cationic rapid setting emulsified asphalt used for fog seals.
Is there any advantage in using an asphalt emulsion over hot asphalt in the chip seal application process?
Asphalt emulsions are applied at much lower temperatures. Thus, there is energy savings and improved safety when applying a chip seal using asphalt emulsions.
What is the process for applying a chip seal?
The chip seal process begins with pothole filling and sealing the big cracks on the existing road surface. These are given sufficient time to dry out before any further application is undertaken. The second process is the cleaning of the road surface by power sweeper or rotary broom in an effort to remove the debris and ensure good adhesion.
Following preparation of the surface, a smooth layer of asphalt emulsion is sprayed using an asphalt emulsion distributor. Next, aggregate chips are evenly distributed across the surface using a truck-mounted or self-propelled mechanical spreader. Aggregate is compressed into the film of asphalt using a pneumatic-tired roller and a proper bond is achieved. After chip seal has cured completely, any loose particles are swept away by booming to achieve a long-lasting, durable, and smooth surface.
Application
Pavement Condition
Cracking
Chip seals are a pavement preservation treatment that depends on various factors such as the existing condition of the pavement, pavement geometry, traffic volume, and materials used. They are most effective when applied to uncracked pavements, acting as a preventive maintenance measure to seal aging surfaces from moisture and oxygen intrusion. While chip seals can seal small cracks up to ¼ inch in width, larger cracks require additional crack sealing before application. Chip seals can also help reduce moisture infiltration in cases of fatigue or alligator cracking, though they may not be effective if the cracking covers more than one-third of the pavement. For block cracking, chip seals can be effective if the damage is not severe. The decision to apply a chip seal requires careful evaluation of the pavement’s condition.
Flushing
A flushed pavement surface is typically soft and experiences a loss of friction, which can cause aggregate to become embedded in the surface after traffic, leading to further flushing. While chip seals can help restore friction, their effectiveness may be limited if the aggregates penetrate too deeply into the flushed surface, unless lower emulsified asphalt application rates are used. Flushing and bleeding are commonly seen in wheel paths, and in such cases, the emulsified asphalt application rate should be reduced in these areas to prevent further issues. This can be done using variable spray rate asphalt distributors or adjusting nozzle sizes on the spray bar. The ball penetration test is a useful tool to measure potential embedment and provides guidance on when a chip seal should be avoided, as discussed further in the construction section of this document.
Surface Texture
Surface texture is a major factor affecting how much emulsified asphalt will be required to hold the aggregate in place. Surface texture of the pavement should be measured prior to application of the chip seal using techniques such as the sand patch test to determine if adjustments to the emulsified asphalt application rate need to be made. If the surface texture changes across the pavement, adjustments in the application rate may be required. It is good to map the surface texture in advance before actual construction to find out which area needs adjustment, especially when some areas have flushed wheel paths, which change the texture.
Summary of Bitumen Emulsion for Chip Seal
Bitumen Emulsion for Chip Seal is an economical and effective solution for preserving and enhancing road durability. Over time, asphalt surfaces can deteriorate due to weather conditions like frost, sunlight, heat, and road salting, as well as the effects of snow removal, overloading, and friction. Without timely repairs or protective measures, damage can progress to complete road surface destruction. Chip seals act as protective layers, sealing cracks, waterproofing the surface, and preventing further wear.
The process involves applying a layer of asphalt emulsion followed by aggregate chips, which are embedded into the surface with a roller. This method not only extends the road’s lifespan but also improves safety and reduces maintenance costs. Chip seals are most effective for low-traffic roads but can be combined with additional treatments, such as slurry or micro-surfacing, for high-traffic areas. Surface texture and pavement condition play critical roles in determining the application rate and effectiveness of chip seals, ensuring proper adhesion and performance.
