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PAVEMENT LIFE - WHAT IS THE TRUTH?
Submitted by Dave Holt, Executive Vice President,
Minnesota Asphalt Pavement Association (MAPA)
Special Projects
If you have been in the Twin Cities of Minneapolis/St. Paul and listened to drive time radio, you likely have heard commercial messages comparing the service lives of Concrete and Hot Mix Asphalt (HMA) pavements. Data from undisclosed sources mentions pavement life for Asphalt is from 7 to 10 years and that the future for Concrete is 60 years or longer.
In 2002, Mn/DOT and MAPA jointly conducted a Pavement Life Analysis for Full-Depth Asphalt Pavements. Mn/DOT provided the data from their Pavement Management System and MAPA provided the funding for the data analysis, which was conducted by Erland Lukanen of ERES Consultants. The analysis shows that full-depth pavements perform as well or better than granular base pavements and, on the average, last three to five years longer than the anticipated 20-year design life.
In an ancillary analysis, overlays on full-depth pavement have a service life in excess of 15 years. Using the data from this study, full-depth HMA pavements, with a resurfacing at the 20-year design life, provide a highly serviceable pavement for an excess of 35 years.
MAPA intends to continue research efforts to verify the service life of granular base pavements and concrete pavements as well. There is presently no analysis available to document the claim that concrete pavements last 35 years, much less 60 years.
The data exists - the public deserves to know the facts!
SUMMARY OF MINNESOTA RESEARCH FINDINGS
By Minnesota Asphalt Pavement Association
The Minnesota Asphalt Pavement Association (MAPA) commissioned Erland Lukanen of ERES Consultants to evaluate the performance history of Hot Mix Asphalt (HMA) Pavements with Aggregate Base and of Portland Cement Concrete (PCC) on the MN/DOT Highway system. The reports on both of these projects are now complete and the results are interesting indeed.
HOT MIX ASPHALT (HMA) PAVEMENTS
- Full-Depth HMA pavements have service lives similar to HMA pavement using aggregate base.
- HMA pavements have average service lives of approximately 18 years. The data indicates that pavements constructed in recent years are performing better, showing the benefit of improved design and quality control techniques.
- HMA pavements are indeed "PERPETUAL PAVEMENTS." Performance data shows HMA pavements lasting 60 years with only periodic HMA overlays.
PORTLAND CONCRETE CEMENT (PCC)
- Fifty percent of PCC pavements are either overlaid with HMA or otherwise removed from service by the time they reach 20 years of age.
- Of the remaining fifty percent of PCC pavements, over 50 percent receive major repair work within the first 20 years.
- MN/DOT's PMS data shows no increase in performance of PCC pavements with time as measured by Present Serviceability Rating (PSR).
CONCLUSIONS
- PCC Pavements have a service life similar in length to that of HMA Pavements, either Full-Depth or Aggregate base design.
- Cost data is not readily available for the various rehabilitation alternatives used on PCC and HMA pavements to allow for direct comparison of Life Cycle Cost (LCC) but the timing of rehabilitation events is similar regardless of pavement type.
Excerpts from an article published in the MAPA Paving Progress Newsletter, March 2002.
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| HOT MIX ASPHALT FACTS |
FACT:
Bituminous (HMA) pavements typically provide 40 to 60 years of service life and receive three overlays in that time frame. The first overlay, on average, occurs between 15 and 16 years after construction, but the most common age for an overlay is 18 years. High volume pavements are often overlaid in the 11 to 15 year old range. That brings the average age at first overlay down to 15 to 16 years of age.
FACT:
The average age of the first overlay of Bituminous Overlaid Bituminous (BOB) pavements is 14.9 years, and the median age is 15 years.
FACT:
Overall, the analysis indicates that the performance of bituminous pavements has improved over the last 10 to 15 years and that pavements constructed now have the potential to provide longer lives than in the past. High severity Transverse Cracking has diminished significantly in recent years. Multiple Cracking, which was the most significant predictor of SR in 2001, is occurring at only a third of what it used to occur at during the 1970's. These types of improvements in performance are consistent with what would be expected from the changes and improvements that have been made in the 1980's and 1990's in asphalt mix design and placement practices.
FACT:
The performance of Full-depth sections constructed under the Quality Management specifications (including modified specified density) is significantly better than sections constructed before.
FACT:
The current data indicates that the Full-depth sections now are performing better than the 1992 models predicted with regards to the SR and similar to the 1992 models for PSR.
FACT:
The 1992 pavement management models indicated that the Full-depth and aggregate base pavements were providing similar performance.
FACT:
The term "Perpetual Pavement" refers to a Hot Mix Asphalt (HMA) pavement design that can be expected to last indefinitely without signs of structural failure.
FACT:
Recent developments, including the Superpave system and Stone Matrix Asphalt designs, have improved the performance of HMA pavements, in particular by extending pavement surface life and eliminating rutting.
FACT:
Every year, more than 73 million tons of asphalt pavement removed from the nation's roads are reused, which makes it America's most recycled product by an impressive margin.
FACT:
The lower cost of HMA pavement translates into better value, too. In almost every case, it is less expensive to build and rehabilitate pavements with HMA.
FACT:
Asphalt has a wide variety of uses, including busy interstate highways, local roads, parking lots, public jogging trails, and bicycle paths. In addition, water reservoirs and fish hatchery ponds are often lined with asphalt.
FACT:
Perpetual Pavements are right for both low- and high-traffic roads and airports because they offer long life under any traffic, infrequent maintenance, a smooth ride, 100 percent recyclability, and reduced noise levels.
FACT:
Production of HMA is known to be environmentally friendly. Although production has more than doubled over the last 50 years, emissions from asphalt plants have been reduced by 97 percent.
FACT:
You can drive on a new asphalt pavement the same day it has been placed. Concrete, on the other hand, generally takes much more time to cure before you can allow any amount of automobile or truck traffic on it.
FACT:
Use of an Open Graded Friction Course (OGFC) design can result in an immediate reduction of noise emissions of 3 to 5 decibels on high-speed roadways, which is the equivalent of a 50 percent reduction in the noise level.
FACT:
A recent study of pavement rehabilitation projects documented that the cost to rehabilitate concrete pavement was 2 to 3 time more expensive than for asphalt pavement. |
| PORTLAND CONCRETE CEMENT FACTS |
FACT:
One half of the concrete pavements are overlaid or reconstructed at between 24 and 25 years of age and at 35 years of age, 88 percent are overlaid or reconstructed.
FACT:
Over fifty percent of concrete pavements have received major repair work (joint repair, diamond grinding, or CPR) within the first 20 years (37 percent have had one major repair and 14 percent have had two).
FACT:
Average PSR performance at 10, 15, and 20 years does not appear to be affected by the year of construction. The typical PSR trend is independent of when the pavement was built. |
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