Maintaining Pavements in a changing Climate
We’ve all seen the news recently reporting climate changes that have caused extreme stress on our transportation and utility infrastructure across the nation. Whether it is failing dams, erosion of highways due to flooding and shifting soils or fires from extreme droughts, climatic changes affect long term performance of these systems. In today’s environment of drastic changes in climates from year to year, it becomes a challenge to understand the forces that continually deteriorate our transportation infrastructure.
The long-term effects of climate changes on pavement are significant. They include significant reduction in stiffness of subgrade and asphalt concrete surfaces, faster deterioration with a drastic reduction of performance life and a faster and non-linear increase in maintenance costs. Such increases in cost are not apparent from predictions that do not consider climate changes. How does pavement performance deteriorate differently with climate change and its uncertainty?
Climatic changes can result in dramatic moisture variations within the soil, more frequent freeze-thaw cycles and extreme temperature variations. These conditions often result in heaving of the roadbed soils, reduced load bearing capacity and erosion of the soils, void formation beneath pavement layers and deterioration of the pavement surface. Do you know when and how often these changes occur within your network? What are the effects on the pavement condition when these climatic conditions occur?
In some regions, an increase in heavy rainfall events may cause extreme erosion, especially in an environment previously in drought conditions. Frequent, long periods of rainfall result in saturated conditions due to a significant increase in the rainfall volumes. Large amounts of surface runoff through pavement edge infiltration, thermal condensation due to these temperature fluctuations and additional moisture infiltration from unsealed pavement cracks all increase the subgrade moisture. Depending upon the climate and region, extreme drying can also occur in the winter.
An increase in frequency of extreme heat days and multi-day heat wave events in the summer, especially in the south, also add to the drying of soils and evaporation of surface water. These climatic factors and environmental conditions affect the pavement structural properties, deteriorate pavement response under loading, decrease pavement performance life and increase the rate of deterioration, resulting in a change in the frequency and type of maintenance and rehabilitation required.
How can we better understand these changes and how they affect our pavement structures? Consistent and accurate pavement condition rating will help you understand the changes occurring in the pavement structure. A regular frequency of condition evaluations every 2 to 5 years will help monitor isolated distresses and provide a better deterioration curve for more accurate prediction of future performance. Survey areas should be equally spaced and marked within the segments to represent the overall conditions, in general conformance with ASTM D6433, such that they can be surveyed consistently for each cycle.
A quick study and review of weather conditions, including seasonal rainfall and temperature changes, will help determine the extent and timing of changes that may be occurring in the pavement system. After severe climatic changes, a small sample condition assessment of select survey areas may indicate if significant deterioration has occurred since the last survey. Understanding how these changes will affect pavement performance will help avoid reactionary repairs and help control costs by improving preventive maintenance.
In addition to pavement condition rating, we also need to understand how the climate changes affect the engineering properties of the pavement materials by reviewing the actual distresses observed to determine what forces may be causing the observed distress. Further engineering evaluations, such as deflection testing, ground penetrating radar or soil sampling may be needed to understand if the distress is related to moisture in the subgrade or other factors that are producing the change in properties of the materials.
A complete review of the soil conditions and properties are vital in understanding the cause of distress and determining the most appropriate maintenance solutions. This is important in not only finding the correct repair, but also in determining the risk associated with potential failure and proper preventive treatments to apply to a pavement structure before the distress occurs.
While proper assessment of the causes for pavement failure is important to determine proper maintenance, when to apply the treatments should be determined through optimization of maintenance for the pavement network. Use of good asset management software, such as VUEWorks, allows users to apply risk factors to the decision process and to quickly perform numerous scenarios to determine which maintenance strategy is the most effective in reducing maintenance costs and maximizing the benefits.
These risk factors can be used to apply more weight on pavement segments with sensitive environmental conditions that may be affected by the climatic changes. According to annual studies performed by the American Society of Civil Engineers (ASCE), the US transportation infrastructure is graded as a D.
With new leadership in Washington, we have heard reports of a new emphasis on funding to improve the condition of our infrastructure, yet each local agency understands this may be too little, too late. Now, more than ever, asset management tools are necessary to keep up with the changing environmental conditions that affect the performance of pavements and the funding needs.
If you are interested in learning more about pavement management best practices and opportunities, please reach out to us!