GMU AND PAVEMENT RECYCLING SYSTEMS

GMU and Pavement Recycling Systems Work to Deliver Sustainable Pavement Engineering Solutions

By Brian Hoover, Senior Editor

Before machines begin grinding up the pavement or pavers proceed to laydown new lifts of asphalt, an engineering firm is hard at work evaluating and testing the pavement, and presenting the various practical and cost-effective pavement repair solutions to their clients. GMU Geotechnical, Inc. (GMU) has been offering full-service pavement engineering services throughout Southern California for more than 50 years. The extent of GMU’s pavement engineering services includes evaluation of existing pavements, design of new pavements, preparation of pavement management plans, development of pavement mix designs, and performing pavement construction observation and testing. GMU provides a full range of geotechnical and related services, including geotechnical engineering, engineering geology, pavement engineering, structural and civil engineering, forensic engineering, and expert witness, as well as soils, materials testing and inspection.

Pavement Recycling Systems spreads cement at rate specified by GMU on a residential community pavement reconstruction project.

Roger Schlierkamp, MSc, PE, is the Director of Pavement Engineering for GMU. Schlierkamp received his master’s degree in civil and environmental engineering, with emphasis on pavement engineering from the University of Nevada, Reno. “I manage anything that is pavement related for GMU, from preparing proposals to final job walk punch lists,” says Schlierkamp. “Our work for clients on the public side includes a long list of agencies throughout Southern California. On the private end, we work with a diverse client base, ranging from large developers such as Rancho Mission Viejo, The Irvine Company and many of the large builders to numerous HOAs all over Orange County and beyond.”

A Dynapac padfoot roller is used for the initial compaction of the cement treated material.

GMU has been involved in many successful and high-profile public works asphalt paving jobs over the past five decades. They have also been an important part of even more small to medium-sized projects. “We begin every new project with a pavement surface condition assessment to consider the pavement distress severity, extent, and type,” says Schlierkamp. “Simply looking at a crack in the pavement is subjective, but when we apply our various test methods, they become very objective,” Schlierkamp says that once they have a general feel for the pavement surface condition, they can begin to assess the likely cause for the distress, such as too much traffic traveling over an inferior subgrade. “We use a variety of testing methods, including drilling pavement core samples, performing falling weight deflectometer testing, conducting ground-penetrating radar testing, performing dynamic cone penetrometer testing, and conducting various laboratory tests in our in-house Caltrans certified laboratory. Depending on the results and findings from these various tests, a solution or solutions are determined and presented to our clients.”

CAT RM500 reclamation machine mixes cement to the specified depth of the cement treatment.

The rehabilitation or reconstruction of a road surface can be accomplished in many ways. There is the old remove and replace methodology. Then there are the sustainable recycling strategies that have been adopted by Caltrans, cities, counties and many private developers and pavement stakeholders. “We recommend and work alongside companies like Pavement Recycling Systems (PRS) who offer a full range of state-of-the-art recycling solutions to rehabilitate pavement surfaces at any stage of its life,” continues Schlierkamp. “The solutions include but are not limited to full-depth reclamation, cement treatment and soil stabilization, cold-in-place recycling and cold central plant recycling methods. Most recently, we have worked with PRS on several HOA and public works projects. PRS is often a subcontractor to the prime paving contractor on these projects. We work right alongside these contracting firms and support the project through the design, construction, and construction testing phase.” Marco A. Estrada, Director of Business Development at PRS, further states, “In addition to the cost and environmental benefits of recycling, these strategies, which are conventional processes in the public works sector, have made the leap into the private sector because of the reduced construction time and the reduced construction traffic realized through the recycling of the existing pavement.”

HOA PROJECT IN LAGUNA NIGUEL

PRS’ fleet of spreader trucks are equipped with vacuum systems to further minimize community impacts.

GMU has been providing its engineering services for one particular HOA in Laguna Niguel, dating back to 2010. “Every few years, this community will carry out a major pavement project to improve certain streets that are due for rehabilitation. We cored the streets that were flagged for improvement this year. We collected subsurface materials and performed an analysis to determine the likely cause of the pavement deterioration,” says Schlierkamp. “We presented them with the cost-effective solution of performing a full-depth reclamation with cement treatment. This strategy reused the existing in-place materials, thereby reducing significant export of in-place materials and the import of new materials. Mission Paving and Sealing was the prime contractor and PRS was their subcontractor responsible for performing milling and pulverization.” Schlierkamp explains that PRS pulverized the existing pavement surface with the addition of cement. “On our projects, we have determined that this particular pavement reconstruction approach saves our clients 30 to 40% in construction costs when compared to older remove and replace methods,” continues Schlierkamp. Acceptance testing procedures utilized by GMU to verify the competency of the cement-treated subgrade included compaction testing using a calibrated nuclear gauge, dynamic cone penetration testing, deflectometer testing, and coring through the cement-treated section.

The FDR-Cement section is open to traffic at the end of every day allowing residents access to and from their homes.

MISSION VIEJO HOA PROJECT IN 2019

FDR-cement minimizes the impact on the residents by reducing construction time and allowing access through ramping of the driveways.

GMU and PRS worked together on another project in 2019 for a private HOA in Mission Viejo. “The project in Mission Viejo was similar to the job in Laguna Niguel and contracted with prime contractor Mission Paving and Sealing and subcontractor, PRS. Again, we recommended full-depth reclamation with a cement treatment,” says Schlierkamp. “We did some cost comparisons and presented our client with a remove and replace option at a unit cost of roughly $9 per square foot. We then presented them with the estimate for full-depth reclamation combined with cement treatment, and that came in at around $4.50 per square foot. They considered everything and went with the full depth/cement treatment option. Both Mission Paving and PRS did an excellent job, and the client was very satisfied with the final product and cost savings, as well as with the reduced community impacts resulting from the recycling process.”

PRS’ Wirtgen 240i reclaimer recycles existing pavement materials in-place resulting in reduced costs and community impacts, while preserving natural resources.

NEWPORT COAST HOA PROJECT

Cement is mixed into the soil to increase strength and improve long term performance in correction of the erosion and rutting of the access road.

Yet another project that GMU and PRS worked together on was for an HOA in Newport Coast. On this job, GMU was faced with engineering a solution to rehabilitate an access road that had been severely eroded from surface runoff over the years. “There were numerous 6- to 10-inch deep ruts in this access road and after evaluation, we recommended pulverization and cement treatment, followed by engineered compaction procedures,” continues Schlierkamp. “Once again, PRS did an amazing job, as did the prime contractor, Premier Paving.”

Adequate compaction of the FDR-cement section further increases strength and enhances the performance of the roadway.

Cement treatment in progress adjacent to custom home construction. Construction time is cut in half as compared to removing and replacing all of the pavement materials.

TRABUCO CANYON WATER DISTRICT ACCESS ROAD REHABILITATION

The Trabuco Canyon Water District (TCWD) needed to have their access road rehabilitated. This particular rural road runs through an environmentally sensitive canyon area and was severely deteriorated. “We presented TCWD with both a remove and replace option and a full-depth reclamation option, which eliminated all export while utilizing the existing on-site materials. The remove and replace option was significantly more costly than the sustainable, recycling option,” says Schlierkamp. “PRS’ feedback on constructability of the full-depth reclamation option for this job was critical during the design phase of this project. This strategy ended up saving TCWD money that could then be put toward other pressing projects.”

Mixing cement into the soil eliminates costly excavation and export of pavement materials, as well as the subsequent import of virgin aggregates.

GMU is on-site testing and inspecting the cement treatment process to ensure compliance with the Engineer’s recommendations.

Schlierkamp points out that sustainable pavement repair strategies have been around for many decades. He says they are built into the Caltrans Highway Design Manual, which is utilized by professionals in this field and that there is an abundance of published papers and guidelines on the subject. “These are all tried and proven pavement strategies that I had studied and learned years ago in college,” says Schlierkamp. “Then you begin working within the industry and see that these methods are not always being used as much as you might expect, and you sort of scratch your head and ask, why not?” Schlierkamp emphasizes that the benefits are just so obvious. He points to significant cost savings and the fact that the methods are so much more sustainable. “There are still those who are not aware of the many benefits. In my opinion, these recycling strategies should be the first to be considered when faced with road rehabilitation and reconstruction needs. Recycling checks many boxes, including lower cost and equal or better performance, as well as the sustainability aspect. These strategies are not limited to wide-open freeways. Some clients may not be as familiar with the process and benefits, and we do what we can to educate them. There is a great deal of science involved if you know where to look and how to apply it.” For more information on GMU and their engineering services, please visit their website at www.gmugeo.com or call their Rancho Santa Margarita headquarters at (949) 888-6513. For more information on Pavement Recycling Systems, please visit their website at www.pavementrecycling.com or call their Jurupa Valley headquarters at (951) 682-1091. Cc

Through sound Engineering and construction, FDR-cement recycles the existing materials in the deteriorated pavement in the construction of the new pavement.

Arizona crossings were constructed at select points of the access road.