DuPage County Illinois Finds Success Protecting Pavements

Studies have shown that longitudinal joints in pavements are often the weakest areas of a road. Typically the joints are low in density, high in voids and thus are highly permeable. These areas become conduits to air and water infiltration which leads to damage and premature pavement failure. (1)

During the 2016 construction season a new method of longitudinal joint construction was specified in Illinois. This new method is a materials approach and is referred to as VRAM(2), a Void Reducing Asphalt Membrane. Applying VRAM at the time of construction helps fill the pavement voids, thus reducing the permeability in this most critical area.

As part of their evaluation, DuPage County ensured that test cores were taken on different joint constructions, such as VRAM and joint heater. DCT, I-FIT, density, and asphalt binder grading tests were performed to compare the different joint construction methods. The report summarized that the addition of the VRAM contributes to a more durable joint by partially filling the joint and adjacent mat air voids. The joint will be much less permeable and less likely to allow water infiltration.

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Success Story: CMS in Iowa

Cationic Emulsions are made up of three major classifications of emulsion grades: rapid-setting, medium-setting, and slow-setting. The terms “rapid,” “medium,” and “slow” relate to the amount of time it takes for the emulsion to cure and the amount of mixing that can be performed before the emulsion breaks. Emulsions that allow for the longest mixing times generally take the longest to cure, while emulsions that allow for very little mixing time are those that set and cure most rapidly.

Chemical surface-active agents, serving as emulsifiers, are classified by the electrochemical charge that is attained when they dissociate in a water solution. In the case of cationic emulsions, the chemical charge is positive. The chemical type and quantity of surface-active agents used in the manufacturing process governs the properties of the emulsion and in what applications the resulting asphalt emulsion can be used.

As many people know, Asphalt Materials, Inc. is made up of a large family of companies. One of these companies, Bituminous Material and Supply, with plant locations in Tama and Des Moines, Iowa, was approached by Denco Construction regarding an interest in using scrub seal in Iowa. This is an emulsion seal that is not often seen in Iowa. A scrub seal is an application that is very similar to a chip seal treatment. The only difference is that the asphalt distributor pulls a broom sled that houses a series of brooms placed at different angles. These brooms guide or “scrub” the emulsion into cracks to help ensure the road’s surface is sealed.

Testing

The scrub seal is a process by which asphalt emulsion is applied to a pavement surface by an asphalt distributor. The emulsion is scrubbed into the cracks and voids with a broom before a layer of aggregate is applied over the asphalt. The scrub seal is then rolled with a pneumatic tire roller and is usually ready for controlled traffic in 1 hour or less. The scrub seal process is intended to rejuvenate dry, oxidized, and cracked asphalt pavements in lieu of a micro-surfacing, chip seal or asphalt overlay. This process was tested on roads that interested counties offered as a demo. Below, you’ll find images that were taken during the testing process.

Results

The evaluation of the demo roads showed success, and Bituminous is now focused on sand applications. Denco Construction purchased a sand spreader during the winter season to fulfill the county’s request.

According to Chris Aldama, Plant Manager at Bituminous, “It’s still a pretty fresh process. Denco was able to take approximately 10,000 gallons at the end of June, but needs to make adjustments on sand suppliers. Once sand quality is finalized, I’m confident in the long term success in this area and beyond.”

To learn more about the process, feel free to watch this video:

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National Air Traffic Control Day: Recognizing Our Work at Coles County Airport

National Air Traffic Control Day was first held on July 6, 1986, on the 50th anniversary of the establishment of the air control system in the United States. According to Senate Joint Resolution 188, which designated the day, it was created to increase public awareness about the United States National Airspace System and to give people a way to “express their gratitude and respect” to “pioneers of the technology of air traffic control” and to all air traffic control personnel.

Many might wonder how National Air Traffic Control Day relates to the work we do here at AMI. The work we do expands far beyond just county roads and highways. We also have experience working with airports because just like with roads, protecting longitudinal joints is also important for airport runways! This past June, we completed a 7,300-foot J-Band project at the Coles County Airport, located near Mattoon, Illinois. The application was scheduled to be 18” wide and 1.51 lb./ft for the 2” surface mix, P401, PG64-22, N40. This was over a recently applied and tacked level binder mix.  J-Band, which is a Void Reducing Asphalt Membrane (VRAM) was measured at 280F after the distributor applied. In total, 7,124 ft and 10,330 lbs. were applied for a total yield of 1.45 lbs./ft. Images of the project can be found below. In Illinois, you may also see VRAM referred to as a Longitudinal Joint Sealant (LJS).

The air control system, created by the United States Bureau of Air Commerce, is the National Airspace System. It works to ensure adequate spacing between airplanes that are flying on routes and to prevent congestion at airports. There are more than 14,000 air traffic controllers, who together with engineers, electronics specialists, and technicians make up the National Airspace System. The system is a model for the world aviation community, is known for its safety and efficiency. Over the course of its first 50 years, the volume of air traffic in the United States expanded one hundred and eighty fold. Today, 5,000 aircraft are in the air in the country at any given moment, with millions of flights taking place each year. The country has 5.3 million square miles of domestic airspace and 24 million miles of airspace over the oceans. On National Air Traffic Control Day, we thank all those who work to keep the airways safe as part of the National Airspace System, and we work to make the system stronger. Learn more about National Air Traffic Control Day here.

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Pavement Rehabilitation and Conversion

AMI is committed to changing the standard in the asphalt industry. Our companies strive to implement new processes, ideas, services, and products with the goal of creating a more effective solution to your road construction projects. Our dedication to quality often results in improving roads through the process of pavement rehabilitation. Each project contains different conditions and construction histories which may alter the approach to conducting pavement rehabilitation, but there are several processes that can be utilized upon reviewing a pavement individually. In general, pavement rehabilitation is suited for pavement in the C, D and F pavement condition zones. This article will address how and when each process is used.

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Comparing Field and Lab CIR Mix Properties: Findings from Indiana SR 234

Any business that has been around for over 65 years should have a strong commitment to innovation. Asphalt Materials is that company. Our teams are focused on helping build longer-lasting, safer roads. To do that, we focus on big challenges as creative problem solvers. We have a unique opportunity available to us and our customers in that we are part of The Heritage Group, which includes the expertise that resides within The Heritage Research Group.

Collaboration is a hallmark of our approach as well. Working with contractors and departments of transportation, we take a collective approach that fosters long-term relationships and mutual trust. A recent project created an opportunity with Indiana State Road 234. The construction project consisted of  126,505 square yards of Cold In-place Recycling (CIR) at a depth of 4-inches. The project length was 10.37 miles with a 22 foot width. The project progression can be seen in the image below.

asphalt project progression

While comprised of similar components to conventional Hot Mix Asphalt, CIR lifts cannot be sampled in the same way to measure and confirm quality of the material. Instead, each CIR candidate pavement is sampled, with the representative materials going through a mix design process designed to closely approximate the CIR construction procedure in the lab. Once the CIR mixture meets or exceeds specified laboratory standards, construction can begin.

Per industry standard, several tests are performed during CIR operations to verify the exact material quantities are added to the mixture per the project’s mix design. In-place density testing is also performed to confirm optimal compaction is reached throughout the placed CIR lift. While this testing method is rigorous for the mixture’s components it does not directly measure mixture performance. The current testing standard reveals opportunities to test the constructed material for performance that is timely from a construction perspective and valuable for agency and contractor customers.

Heritage Research Group designed a field sampling method to sample constructed CIR materials just prior to field compaction, allowing for test specimens to be produced and performance tested, similar to mix design test specimens in the lab.

Additionally, a rare opportunity arose to sample the CIR by coring, shortly after construction and the final HMA overlay was completed. This provided field cores from the project for further analysis that is truly representative of the mixture.

Six, 6-inch cores were collected from eight locations on the project (see example below).

core testing

Based on these testing and material sampling opportunities, a research project was formed as follows:

  • Evaluate sampling procedure for field-collected samples.
  • Compare mix design results to field-collected samples.
  • Quantify impact of delayed compaction of field samples.
  • Compare mix design, field samples to field cores.

The variation in approximated versus representative processes in the three types of CIR samples provide a unique perspective to confirm accuracy of the field sampled mix tests and of the initial mix design test results. A diagram outlining the differentiations between mix design, field samples and field cores can be viewed below.

project truth scale

All of the CIR processes are approximated in the lab to produce a mix design, while field sampled materials contain more accurate versions of these processes because they are sampled from the constructed lift. Finally, cores collected from the project, several months after the CIR was completed, provide the most accurate version of the mixture, all of the CIR processes, including compaction, being true to the constructed CIR. 

After conducting testing to determine air voids in the mixtures, specimens were tested for marshall stability and indirect tensile strength in dry and wet conditions. These results are used to estimate a mixture’s resistance to water damage, rutting, and cracking in tension.

To further understand the long-term performance of the mixture, dynamic modulus testing was performed with small-scale AMPT specimens collected from the CIR pavement cores.

Several findings were determined upon analysis of the test:

  • The sampling method to collect field mix samples for lab compaction and testing could be a method to verify CIR mixture properties in the future.
  • The dynamic modulus test results provide additional data to the industry on the performance qualities of the constructed mixture, which also align with the current industry recommendations for the mastercurves which characterize CIR materials. 

This project is an excellent case study that demonstrates the outcomes that are possible when different groups are all driving to the same goal of creating longer lasting, safer roads.

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Rebuild of County Road 151 recognized with two awards

The rebuild of County Road 151 across three townships has been honored with two awards. 

The Monroe County Road Commission received the national Asphalt Recycling & Reclaiming Association’s 2016 Award for Excellence in full-depth reclamation for the project. In addition, the road commission and Gerken Paving Inc. received an award of excellence from the Asphalt Pavement Association of Michigan. 

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