Best Practices for Asphalt Parking Lot Maintenance Introduction: Parking lot pavement is typically designed to last between 20 and 40 years, but examples of parking lots that don’t need to be replaced until long after the end of their design life are common. Timely, appropriate maintenance often makes the difference. This document will help you evaluate your current parking lot pavement, develop a maintenance plan appropriate for the present pavement condition, and anticipate how much can be saved by timely maintenance instead of allowing this valuable asset to deteriorate and fail prematurely. Evaluation: Severity, extent, and type of distress are the primary factors used to evaluate pavement. The entire parking lot should be surveyed, noting the type of distress present at each deficient area, how large the deficient area is, and classifying the severity of each deficiency as low, moderate, or high. Once you have a listed the type, size, and severity of distress at each deficient area, the appropriate corrective process can be determined. For a 30,000 square foot parking lot this may look like Table 1. Types of distress are discussed in detail in Appendix A. Type Pothole Pothole Block Cracking Block Cracking Patch Deterioration Extent 12 locations, 40 sq. ft. 6 locations, 30 sq. ft. 400 sq. ft 500 sq. ft. 100 sq. ft. Severity Moderate Severe Low Moderate High Reconstruction, Rehabilitation, and Maintenance: After pavement has been evaluated, a plan to correct existing deficiencies and proactively maintain pavement to keep it in good condition should be created and implemented. This plan should be developed for the length of time the owner expects to retain the property, since longterm plans are best for anticipating capital needs. Keep in mind that paving technology changes rapidly, which means anticipated maintenance may be modified or replaced with newer processes and products. The maintenance plan should be divided into two phases Preventive Plan: Preventive maintenance should be performed as a proactive measure to keep pavement in good condition and generally consists of crack repair, application of sealcoat and slurry seal, and thin overlays as needed to address normal wear and tear. While these maintenance operations are sometimes used to try to wring a couple more years of life out of pavement in need of reconstruction or rehabilitation, this is generally a waste of money. Once a parking lot is in fair to poor condition, (XX% or more showing any level of distress) it is more economical to suspend maintenance operations and apply the maintenance budget to future reconstruction or rehabilitation. Annual Maintenance: Cleaning and crack sealing. Keeping pavement free of debris and sealing cracks and joints annually will help prevent standing water that can cause damage. Wide cracks (greater than 3” in width) – need patching or other, Cracks that are 1” - 3” in width, use a mastic repair. 5-Year Maintenance: Annual maintenance plus seal coat. The purpose of a seal coat is to renew the asphalt surface that has worn off of the top layer of aggregate or been oxidized and to seal the pavement surface to help keep water from entering the tiny voids that allow asphalt to expand and contract seasonally. 10-year maintenance: Annual maintenance plus slurry seal. The purpose of slurry seal is much the same as seal coat except that it also replaces some of the thickness that may have worn away in heavy traffic areas and can fill minor ruts. 15-year maintenance: Same as 5-year maintenance 10-year maintenance: Thin overlay to renew the wearing surface and address any areas that have developed low-severity distress. Corrective Plan: The corrective plan may consist of reconstruction or rehabilitation. Reconstruction is generally the best approach if more than XX% of the parking lot shows moderate or severe distress. Historically, this has meant removing the existing pavement, scarifying and re-compacting base material, then placing a new asphalt mat (typically 3” to 5”) in accordance with a geotechnical engineer’s recommendations. A more environmentally friendly and often more cost effective approach is to recycle existing pavement in place using a process called full depth reclamation (FDR). This process grinds up existing pavement while mixing it into the existing base. The resulting material is then compacted, resulting in a thicker, higher quality base that will provide the same performance with a thinner asphalt mat than is possible by removing and replacing the pavement. Recycled asphalt has long been recognized as an excellent road base – why not re-use it without the expense of trucking it to a storage facility first? Rehabilitation usually consists of repairing potholes and other localized deficiencies followed by a thin overlay (≤ 1 ½”) or milling to remove distressed surface material and placing a thicker overlay. Core samples may need to be taken to determine how much material should be removed and how thick the overlay should be. A rule of thumb is to consider rehabilitation if less than XX% of the parking lot area shows moderate or high distress. Whether the parking lot is reconstructed or rehabilitated, care should be taken to ensure that the pavement has enough slope to maintain positive drainage and prevent “bird baths” and other areas of standing water. Asphalt pavement has a small percentage of voids which are necessary to allow seasonal expansion and contraction. Water that doesn’t drain quickly can trickle into these voids causing freeze-thaw damage to the pavement and eventually weakening the base course and compacted soil beneath the pavement. Drainage problems are frequently a major cause of parking area pavement failures. This is especially the case with irrigation sprinkler systems located in parking lots and medians. It is critical to keep water away from the subgrade soil. If the subgrade becomes saturated, it will lose strength and stability, making the overlying pavement structure susceptible to breakup under imposed loads. Drainage provisions for islands and other vegetated areas should be verified (or installed, if not present) as part of every parking lot reconstruction or rehabilitation. Maintenance Budget: The attached table shows typical costs (in 2013 dollars) for common maintenance treatments. Treatment Cost Service Life Crack fill Seal Coat Slurry seal Thin Overlay XX XX XX XX Annual 5 years 10 years 20 years Cost Per Year of Service Life XX XX XX XX The following 50-year life cycle cost analysis shows how aggressive maintenance can save money in the long run.