Asphalt / Hot mix Release Agents

Asphalt and Hot Mix Release Agent

Asphalt Release Agents are chemical products developed and manufactured as alternatives to diesel and solvents commonly used for cleaning equipment associated with Hot Mix Asphaltic Concrete (HMAC) production and placement on government and private facilities. 

The intent of asphalt release agents is to eliminate harmful stripping products that come into contact with bituminous products and strip the asphalt (binding agent) from the aggregates causing potholes, raveling, and other detrimental pavement failures.

True asphalt release agents are biodegradable and do not pose a health risk to workers or an impact on the environment.  When used properly, they provide a barrier to the bituminous mixes and allow for very little cleanup of the equipment at the end of the day. 

Economy - Safety - Sustainability

Asphalt release agent is applied as a liquid, and frequently reacting with the heat of the mix, barrier release agents form a physical film preventing the binder from bonding to the surfaces at the plant, in the trucks and out with the crews. To meet specs, barrier products cannot react with asphalt binder, helping to promote good quality control and mix performance. Today’s release agents cover all applications of the paving train, and economy with performance is commonly achieved. 

Asphalt release agents can help responsibly save money and enhance best practices at the plant and with the paving crew. Framed in three sustainability points:

1) Environmental Stewardship

A policy of choosing non-hazardous products whenever possible helps to protect your employees, your customers and your community. In addition, a national testing protocol must be initiated for asphalt release agents. Using an approved release agent chemical helps to assure safety and performance. Plants and construction sites are also required to maintain good storm water compliance. Storm water-compliant release agent products that pass state and national tests bring obvious benefits versus risking diesel contamination.

2) Social Benefit

Many companies recognize their responsibility in the community and run environmentally friendly programs. Eliminating hazardous chemicals from plants and construction sites helps make us good neighbors. Taking care of employees and reducing sources of site liability are prime goals of many sustainability plans. 

3) Economics

The newest generation of asphalt release agents has emerged offering a cost per ton below diesel with strong performance against modified binder mixes. A good release agent today can cost as little as 20 cents / ton and still see clean beds. Given that trucking continues to be a scarce commodity in many markets, saving an hour or so of haul time per day for each truck on the job can be significant. Out with the paving crew, on-board spray systems with a release agent tank can reduce clean up time dramatically, while achieving better performance and lubricating critical equipment. Release agent spray systems with tanks are standard on most new pavers, MTVs and shuttle buggies. 

Tests to evaluate asphalt release agents

Every contractor that works around asphalt hot-mix (whether hot, warm, or cold) has experienced the need to clean up equipment on a daily basis. For decades, this has been done with readily available diesel and solvents. However, in performing this task, they are also causing the asphalt to “soften” and strip off of the aggregates. Without this “glue,” the mix quality is compromised.

People designing, constructing and maintaining roadway systems have recognized the need to preserve the integrity of the asphalt hot-mix and protect the environment.

Asphalt Release Agent is now a general term used for products that have been developed to replace the stripping and environmentally hazardous diesel and solvents. A new test procedure and specification for asphalt release agent required it in their specifications.

In 2015, Australian Asphalt Pavement Association (AAPA) acknowledged the multiple testing programs by the State Department of Transport (DOT) and accepted the task of testing and reporting results of asphalt release agent products on a standardized national level. This work plan consists of three test procedures: a stripping test, a mixture slide test and an asphalt performance test.

Asphalt Stripping test

Asphalt Stripping test

The stripping test involves taking a vendor’s product, filling up a quart jar and placing actual hot mix into the solution. Based on the liquid discoloration, it is reported as “No Stripping.” “Slight Stripping,” “Moderate Stripping” or “Severe Stripping.” Additionally, a visual check of the hot mix is performed to see if the asphalt is stripping from the aggregate. The visual check is done for very dark to opaque products.

Asphalt Mixture slide test

Asphalt Mixture slide test

The mixture slide test involves the use of an actual plate cut out of a truck bed. Hot mix is placed on the plate where the asphalt release agent is sprayed. After a specified time, the plate is tilted to see how much of the mix slides off. This test simulates the effect of mix in truck beds.

Asphalt performance test

Asphalt performance test

The asphalt performance test involves the application of asphalt liquid poured onto the same truck bed plate. After a certain rest period, the asphalt “patty” is lifted from the plate. An accumulative weight is recorded until the specified percentage is achieved. This test simulates asphalt sitting on items like the pavers, rollers, rakes, lutes, shovels and elevator slats at the hot mix plant.

Many other states are now looking at their asphalt release agent program and quality products list. The concept is catching on with the DOT and industry professionals to help create and place quality mixes, to provide a long lasting pavement to the traveling public and protect the environment.