Diamond grinding creates a smooth, uniform pavement profile by removing faulting, slab warping, studded tire wear, and unevenness resulting from patches.

Although shovel-ready projects are needed to inject money into the economy at a rapid pace, specifiers must be careful not to throw their money at short-lived, temporary pavement repair solutions in their haste to spend the stimulus funds quickly. For local streets and highways, it is crucial that investments are made in long-lasting, cost-effective rebuilding projects.

Concrete pavement restoration (CPR) projects offer a long-term repair solution engineered to last many years, even decades, and they can be designed and packaged for bid in a matter of days. Further, stiff competition within the industry and advancements in technology ensure that CPR pricing is typically far less than alternative repair treatments. Motorists will benefit from the resulting smooth, safe, and quiet ride when pavements are treated using CPR.

How it works
CPR is a series of engineered techniques developed during the last 40 years to manage the rate of pavement deterioration in concrete streets, highways, and airports. It is a non-overlay option used to repair areas of distress in concrete pavement without changing its grade. This preventive procedure restores the pavement to a condition close to or better than original and reduces the need for major and more costly repairs later. Further, CPR addresses the causes of pavement distress, minimizing further deterioration. In contrast, covering the distress with an asphalt overlay does not correct the cause of the distress and it will eventually manifest itself again, usually as a larger, more expensive problem.

Basic CPR techniques include the following:

Slab stabilization — This technique restores support to concrete slabs by filling small voids that develop underneath the concrete slab at joints, cracks, or the pavement edge.

Full-depth repairs — This procedure is a way to fix cracked slabs and joint deterioration by removing at least a portion of the existing slab and replacing it with new concrete.

Partial-depth repairs — This method corrects surface distress and joint-crack deterioration in the upper third of the concrete slab. Placing a partial-depth repair involves removing the deteriorated concrete, cleaning the patch area, placing new concrete, and reforming the joint system.

Dowel bar retrofits — This method consists of cutting slots in the pavement across the joint or crack, cleaning the slots, placing dowel bars, and backfilling the slots with new concrete. Dowel bar retrofits link slabs together at transverse cracks and joints so that the load is distributed evenly across the crack or joint.

Cross-stitching longitudinal cracks or joints — Cross-stitching repairs low-severity cracks. This method adds reinforcing steel to hold the crack together tightly.

Diamond grinding — By removing faulting, slab warping, studded tire wear, and unevenness resulting from patches, diamond grinding creates a smooth, uniform pavement profile. Diamond grinding also reduces road noise by providing a longitudinal texture, which is quieter than transverse textures. The longitudinal texture also enhances macro texture and skid resistance in polished pavements.

Joint and crack resealing — This technique minimizes the infiltration of surface water and incompressible material into the joint system. Minimizing water entering the joint reduces subgrade softening, slows pumping and erosion of the sub-base fines, and may limit dowel bar corrosion caused by deicing chemicals.

Next generation of concrete surfaces
In addition to CPR techniques — proven to result in safe, durable, and environmentally sustainable solutions for the driving public — tire/pavement noise has become a hot-button issue in areas with large populations and high traffic volumes. Public officials have increasingly sought long-lasting, economical, noise-reducing surfaces for their pavements. The Next Generation Concrete Surface (NGCS), now in the testing stage, is proving to be an ideal solution to meet these needs.

In 2005, the Portland Cement Association, through the American Concrete Pavement Association (ACPA), funded research to improve the noise performance of concrete pavements. The International Grooving & Grinding Association (IGGA) and its affiliated contractors supported the research effort through equipment development and test section construction.

NGCS pavements, designed to provide a consistent profile absent of positive or upward texture, describe a category of textures that have or will evolve through current research.

NGCS is a hybrid texture constructed on concrete surfaces that resembles a combination of diamond grinding and longitudinal grooving. The texture can be constructed as either a single-pass or two-pass operation using diamond tipped saw blades mounted on conventional diamond grinding and grooving equipment. These textures, for both new construction and rehabilitation of existing surfaces, will have the desirable characteristics of a very smooth profile coupled with good micro texture and excellent macro texture.

According to Larry Scofield, director of pavement innovation for the ACPA, NGCS is still in the development stage and as more is learned through research, the configuration of the surfaces may change.

“Since the NGCS is more of a ‘manufactured’ surface, it is more consistent and predictable than traditional surfaces,” commented Scofield. “NGCS and conventional diamond grinding are competitive with all surfaces from a noise-reduction perspective.”

Purdue University’s Herrick Laboratories of West Lafayette, Ind., conducted the research using its Tire Pavement Test Apparatus (TPTA). The TPTA allows evaluation of texture designs unconstrained by current construction capabilities or costs associated with field test section construction and evaluation, and without the resulting traffic control or safety issues. The Purdue work evaluated the variables affecting the construction of diamond-ground textures and the joint-slap effect associated with transverse joint noise generation. Test findings indicated that the geometric configuration of the blades and spacers used to construct diamond-ground textures was not the controlling factor in noise generation, but rather, the resulting fin profile was the most important factor. Producing a low-noise diamond-ground surface required creating uniform and consistent land profiles.

To verify this finding, a new surface — NGCS — was created that consisted of a uniform land profile design with essentially all negative texture. This surface texture produced the lowest tire-pavement noise levels in the study. The surface was then constructed in the field using diamond grinding equipment to confirm the laboratory study.

NGCS field-tests currently exist in Minnesota, Illinois, and Wisconsin with a fourth planned for Seattle, Wash. The field test sections allow evaluation of the NGCS effectiveness under various traffic conditions and concrete pavement construction scenarios.

Scofield noted that with the array of aggregates used to construct concrete pavements, it is important to evaluate both the acoustic and frictional longevity of these surfaces when they are constructed on different types of concrete. Through field evaluations, contractors will get a better understanding of the constructability of these surfaces and their cost effectiveness.

Along with development of the new surface, NGCS LITE was created to provide an economical renewable surface for NGCS. Designed as a “perpetual surface texture,” NGCS LITE offers an efficient method for enhancing the micro texture on the land area of the NGCS. Since very little material removal is necessary, this process is fast, cost efficient, and is an excellent concrete pavement preservation tool.

For the test sections constructed to date, the NGCS begins approximately 1-4 decibels adjusted (dBA) quieter than a conventional diamond-ground surface, and is approximately 0-1 dBA quieter after the first year. Although more time is required to establish the acoustic performance of the NGCS pavement, it is not expected to change within the first 10 years of its construction, provided it is implemented on well-designed concrete pavements constructed with high-quality, durable aggregates.

As NGCS technology continues to develop, more testing will be conducted to further evaluate these new surface textures. The NGCS represents the concrete industry’s most significant advancements in achieving quieter concrete pavement surfaces to date. All of the NGCS validation tests in the field have demonstrated successfully that it is a very-low-noise concrete surface. It provides low-noise benefits when constructed and does not require a wear-in period to break down the fins.

Call to action
In these challenging times, our country needs innovative, environmentally friendly, pavement optimization and rehabilitation solutions that can stand the test of time and traffic. Now, more than ever before, it is crucial that investments are made in long-lasting, cost-effective CPR treatments.

John H. Roberts is executive director of the International Grooving & Grinding Association (IGGA), a non-profit trade association committed to development of the diamond grinding and grooving process for surfaces constructed with portland cement concrete and asphalt. In 1995, the IGGA joined in affiliation with the American Concrete Pavement Association (ACPA) to represent its newly formed Concrete Pavement Restoration (CPR) Division. The IGGA/ACPA CPR Division now serves as the technical resource and industry representative in marketing optimized pavement surfaces, concrete pavement restoration, and pavement preservation around the world. For more information, visit www.igga.net.