By Scott Sounart, PE
Parking lots play a vital role in the success of the buildings they serve, serving as a de-facto lobby and delivering the initial impression of the property. A run-down parking lot creates an unattractive and unwelcoming image that makes the entire complex seem less appealing and inviting. Perhaps more importantly, a derelict lot can also pose potentially hazardous conditions for visitors and employees and their vehicles. Not only can this undermine a business by making it’s location less attractive to potential customers, but it can also lead to costly legal liability if visitors or employees suffer personal injury or damaged vehicles.
Yet, in spite of the obvious hazards that can be caused by run-down or improperly maintained parking lots, many owners treat their lots as an afterthought. This is partly a perception problem. Many owners develop lots rather than a parkade because they mistakenly think that parking lots are essentially maintenance-free. They assume that they can just pave over an area of land, paint in stripes for spaces, and forget about it.
While it’s true that the typical lot requires less maintenance than a parkade, maintenance is required. Sure, there are no concrete ramps, floors, or support columns to care for, but a parking lot’s pavement undergoes a great deal of wear and tear every day from multi-ton vehicles, rain and snow, and even the rays of the sun. As such, it’s essential to have an assessment and maintenance plan to preserve the property’s aesthetics, ensure customer and tenant safety, and extend the service life of the pavement.
Pavements can be one of a commercial facility’s most expensive assets to maintain, but these costs can be minimized. There are seven primary types of asphalt distress, any one of which can require repair. The good news is that a pavement evaluation program, led by a trained and experienced pavement assessor, can identify potential problems before they require major overhauls, saving owners and their property managers tens of thousands of dollars.
7 Signs of Trouble
There are seven common types of asphalt deterioration, and they tend to progress from one to another. The first sign of trouble appears in the form of longitudinal cracks. Longitudinal cracks typically appear along joints, which are the weakest part of the pavement. They can result from poor joint construction or location, or they may be an indication of fatigue within the stabilizing base below. Even though longitudinal cracks are just an early form of deterioration, they can cause major problems down the line by allowing moisture to infiltrate the concrete.
The next common form of deterioration is transverse cracking, which extends across the pavement perpendicular to longitudinal joints. Transverse cracking usually results from shrinkage of the stabilizing base below and is often related to low temperatures impacting the asphalt. Transverse cracking is also often an indication that the stabilizing base is also cracked. As longitudinal and transverse cracking increase in magnitude and density, they form block-like patterns called block cracking. Block cracking is a series of interconnected cracks that appear as rectangular pieces, or blocks. Like longitudinal cracks, block cracking can also allow moisture to infiltrate the asphalt, which can undermine the pavement.
When aggregate or asphalt binder materials wear away at the surface, raveling results. Raveling is essentially the disintegration of the asphalt surface causing pieces of the pavement to come loose. This can lead to gaps within the pavement surface, roughening of the surface, and loss of binder, and thus protection from moisture.
While these first four types of deterioration are signs of trouble, they can often be treated with inexpensive preventative maintenance procedures such as a crack seal or seal coat. Unfortunately, many owners and their maintenance consultants unnecessarily utilize more costly reconstruction, and as a result end up spending thousands more than necessary to fix what are essentially simple and common issues.
That said, higher density cracking and higher severity raveling often do require more involved and costly interventions. For instance, rutting is a permanent deformation of the pavement that occurs when ruts appear in the subgrade beneath the pavement. The formation of ruts can lead to ponded water, which can lead to vehicle hydroplaning and other related problems. There are two basic types of rutting: mix rutting and subgrade rutting. Rutting is often the result of initial construction or design techniques, such as inadequate pavement structure or insufficient compaction of base layers during construction. When the subgrade is no longer able to support the pavement structure, fatigue cracking will set it. Fatigue cracking, or alligator cracking, resembles an alligator skin’s diamond-shaped pattern. Both rutting and fatigue cracking are indications that, in addition to the obvious surface deterioration there is also significant corrosion within the asphalt. Left untreated, these issues cause the pavement to settle or depress, which ends up forming a pothole.
These more advanced forms of deterioration typically call for mill and overlay rehabilitation, a much more expensive form of rehabilitation. As such, it is imperative to identify the warning signs and resolve early premature distress before these major—and much more expensive—problems appear. Parking owners and their operators should be vigilant about monitoring the condition of the pavement in their parking lots. They should keep to a regular schedule of inspecting pavement surfaces, and staff should be trained to identify the various types of deterioration by sight. In parts of Canada that experience particularly inclement weather and wide fluctuations in temperatures, it may make sense to hire a pavement consultant to monitor pavement condition and implement maintenance fixes before they turn into major problems.
When it’s apparent that potentially significant pavement damage is already emerging or may be already present, it is advisable to turn to a pavement specialist with experience in geotechnical engineering, observation and testing for pavement design, and expertise in all aspects of pavement engineering, including surface and subsurface investigation, pavement evaluation, forensic failure analysis studies, pavement design, pavement management systems, and construction quality assurance and quality control. Pavement responds differently to different types of uses, as well as different climates. It’s important to have a comprehensive pavement maintenance and repair strategy that takes into account all of the issues that can impact the pavement’s performance and lifespan. When planned and implemented appropriately, a parking lot’s pavement management program can extend the useful life of the lot by many years and save the owners tens of thousands of dollars by avoiding unnecessary repair and replacement costs.
Scott Sounart, PE is a Senior Principal with Kleinfelder and Director of the firm’s pavement engineering practice. He can be reached at SSounart@kleinfelder.com.