Strategies to Prevent Water Damage in Asphalt Pavements
Water is a primary cause for asphalt pavement deterioration, leading to structural failures such as cracking, potholing, and base course damage. Prolonged water exposure exacerbates these issues. Such pavements require timely and effective maintenance strategies to extend the service life and overall performance of the pavement. In this blog, we discuss four key strategies to protect the asphalt pavement from water damage: seal coating, crack filling, crack sealing and pothole repair.
Seal Coating
Seal coating is a preventative maintenance technique involving the application of a protective liquid layer over the asphalt surface. This process serves several critical functions:
Oxidation Resistance: Prevents the oxidative hardening of asphalt, which can lead to brittleness and cracking.
Chemical Protection: Shields the pavement from chemical spills and reactions.
Waterproofing: Reduces water infiltration, thus safeguarding the base and subgrade from moisture-induced damage.
The optimal frequency for seal coating is every three to five years, based on environmental conditions and traffic loads. It is important to note that seal coating is a maintenance measure rather than a corrective solution. It is ineffective in addressing underlying structural deficiencies within the pavement base.
Crack Filling
Crack filling is a crucial reactive maintenance task designed to prevent water from penetrating pavement cracks. As asphalt oxidises, it becomes more brittle, making the pavement more susceptible to cracking under traffic loads. These cracks allow water to enter, undermining the structural integrity of the base course and reducing the pavement’s load-bearing capacity. Timely crack filling is essential to avoid repeated water-related damage.
This process involves using cold-patch or hot-patch asphalt to fill larger, nonworking cracks and holes that sealing alone cannot adequately address. Nonworking cracks, typically less than 0.25cm wide, include block, longitudinal, or diagonal cracks that do not move due to the close proximity of their edges. Filling is recommended when the pavement shows minimal movement, as it offers a more permanent and durable solution for deeper and wider cracks.
The materials used for crack filling are not rubberised, as minimal flexibility is required. The equipment needed for this process is relatively simple, usually consisting of a shovel, a tamper, pressurised air, and the patch mix.
Crack sealing
Crack sealing is the preferred method for addressing smaller, more manageable cracks. Though the process is quicker and suitable for minor repairs, it requires more specialised equipment, such as tanks, melt pots, and torches. Sealing involves cleaning out the crack and injecting hot sealant into or over the crack, effectively sealing it to prevent water from penetrating the crack and reaching the subgrade.
Sealant is used when cracks are in their early stages to prevent them from expanding into more significant issues. Cracks should be shallow and less than 0.75cm wide; anything larger may require filling instead. Although sealing is more expensive due to the tools and materials required, it offers better value in the long run because it lasts longer and provides more durable protection than filling.
Pothole Repair
Potholes are symptomatic of significant base course failure and surface oxidation. The process involves the disintegration of asphalt aggregates and the formation of depressions due to water-compromised bases. Traffic increases the displacement of these aggregates, leading to additional potholes.
Various pothole repair materials are available, from cold patching which provides a short-term solution, to the use of spray injection devices. Cold patch repairs are temporary fixes that use premixed asphalt. Comprehensive repair such as hot patch repairs provide a more permanent solution by applying hot asphalt. For extensive damage, a full-depth repair involves completely removing and replacing the affected area.
Prior to carrying out any works, it is recommended for asset owners carry out detailed condition assessments of pavements. The LCMS-2 profilometry vehicle is highly recommended for assessing roads with reoccurring potholes.
Protecting asphalt pavement from water damage is critical for its longevity and functionality. While repaving is a common budget consideration for property managers, a thorough pavement evaluation can help determine if alternative maintenance measures are more appropriate. Preventative tasks such as seal coating, crack filling, crack sealing and pothole repair can significantly delay the need for repaving, optimising maintenance budgets and prolonging pavement life.