Common Causes of Pavement Failure

Premature pavement failure is classified as any major defect that occurs within the design life of the pavement. Many premature pavement failures are chronic in nature, and many of these reoccur even after maintenance activities. Premature defects can be addressed by identifying and addressing primary root causes of pavement failure during the design process.

Let’s have a look at the six main causes of premature pavement failure in further detail:

1. Poor soils

While some materials are very hard and make a good base, others are unstable, meaning that they are more susceptible to failure under loads. A well constructed pavement must have a good foundation. If the subgrade is unstable, the pavement will fail prematurely. Good soils are typically contain sands, gravel, and clays (although clays can be affected by moisture). Furthermore, some materials, while hard when dry, can change drastically when they get wet. When introduced to an excessive amount of moisture, some materials become fluid and unstable while others expand, causing heaving. Bad soils like topsoils and organic soils (e.g. peat) are usually removed before a pavement system is installed. Too often organic materials like topsoil are not completely removed before the stone base and pavement is installed. Layers of organic material are, by nature, unstable and should never be used as the foundation for a pavement. Soft subbase materials make it impossible to obtain proper compaction of the stone base and asphalt.

2. Drainage

The presence of moisture, surface and subsurfaces is detrimental to any pavement system. Water ponding on a pavement will cause surface deterioration. Proper surface drainage and cracks sealing/joint sealing is critical to the life of a pavement. Subsurface water softens subgrade and subbase materials, weakening the pavement foundation. Water infiltrates into the subsurface from springs, surrounding soils, utility lines, and through cracks or joints in the pavement. Once water infiltrates the pavement system, it softens the subgrade and subbase, resulting in pavement failure. For example, a carpark pavement becomes damaged from water in the adjacent turf. Water from the turfed areas infiltrates and softens the base, causing areas of failure. Water is running across the parking lot, dumping water into the landscaped area, and water sweeps back under the pavement. The cars park right up to that edge, exactly where the damage is occurring.

3. Traffic usage

Unplanned use of a pavement can cause failures. For example, the use of car parking areas for truck traffic or construction staging areas can cause damage and premature pavement failure. Knowing the planned traffic usage is critical to preventing premature pavement failure. Bus and truck traffic require more robust pavement systems. Heavy forklift traffic or not utilising concrete pads for trailer landing gears can lead to pavement failure.

4. Improper materials

Not every crushed aggregate, concrete or asphalt mix performs the same. Matching the right material for the right project will reduce premature failures. Some crushed aggregates compact and bind together better than others, resulting in stronger foundation. Rounded gravels are more unstable and can lead to base failures. Concrete pavement very greatly for strength and durability. The wrong mix or reinforcing steel can cause premature failure. Matching the right material with given conditions reduces the chance of failure. For instance, a driveway asphalt mix may have a smoother appearance, but will not have the strength needed for a commercial application.

5. Improper design

An inadequate pavement design does not have sufficient thickness of aggregate base and pavement to overcome deficiencies in the subgrade soils and planned traffic usage. Even concrete will fail if there is not stone base and the pavement is too thin. Root causes of pavement failure must be addressed in the design phase or failures will occur.

6. Not following design / lack of construction oversight and quality assurance

Even the best design is rendered inadequate if plans and specifications are not followed during construction installation. Lack of construction oversight, inspection, and quality assurance can lead to premature pavement failures. For example, material quality control will ensure the asphalt is being produced as specified. With inspection, deficient areas of subgrade or subbase can be corrected in the field and not just paved over. Unforeseen water issues can also be identified and steps taken to keep the pavement system dry.

All too often pavement are constructed without addressing the issues that caused the pavement to fail in the first place. By taking precautions against the six causes of premature pavement failures, you can assure that your new pavement will perform as expected.