Strategies To Improve The Sustainability Of Asphalt And Concrete Pavement Construction Operations
Pavement construction practices have changed significantly over the last several decades as new technologies have been developed that offer the potential for significant improvements in pavement quality and construction efficiency while decreasing environmental impacts. These construction practices, in concert with an appropriate pavement structural designs that use appropriate materials, can provide significant improvements to the overall sustainability of a pavement system. Critical areas of pavement construction that can have a significant effect on the overall sustainability of a paving project include:
- fuel consumption (during material transport from the site and between the plant and the site and the construction operations themselves);
- exhaust and particulate emissions;
- traffic delays, congestion, and noise emissions generated during construction;
- constructed characteristics of the pavement surface, which can impact surface friction (safety), noise, and use phase fuel efficiency; and
- impacts on pavement performance and overall service life as a result of construction quality.
Tables 1 and 2 list general approaches to improving the sustainability of asphalt and concrete pavement construction operations, respectively, and summarize the key economic, environmental and societal impacts of each approach. Chapter 5 (.pdf) of the Reference Document provides a more detailed presentation and discussion of each approach and impact.
| Objectives | Approach for Improving Sustainability | Economic Impact | Environmental Impact | Societal Impact |
|---|---|---|---|---|
| Achieve Target Density Requirements | Increase lift thickness to nominal maximum ratio with aggregate size. | Potential cost reduction with reduced number of lifts constructed. | Better resistance to top-down cracking. Reduced environmental impact with improved performance and longer life (fewer M&R activities, less frequent reconstruction). | Less frequent traffic disruption with improved performance and longer life. |
| Use warm-mix technologies. | Potentially increased costs due to additives and capital investment. | Reduced environmental impact with reduced fuel consumption for lower compaction temperatures. | Reduced construction- related air pollution and irritation potential for sensitive workers. | |
| Follow laydown temperature requirements. | No change in cost. | Reduced fuel consumption and emissions when required mat thickness and density are achieved in fewer passes. | Reduced incidence and length of traffic delays with faster, higher quality construction. | |
| Select proper placement and compaction equipment with “smart” technology. | Increased contractor capital investment costs and associated increased agency costs, but increased long-term benefits to contractors (construction efficiency) and agencies (performance). | Reduced environmental impact through improved performance and longer-life pavements due to use of improved construction techniques. | Longer pavement life with fewer disruptions due to M&R activities. | |
| Prevent Segregation | Use thermal cameras to avoid erratic mat temperatures and temperature-related segregation. | May increase contract costs due to capital investments in equipment. | Reduced environmental impact through improved performance and longer-life pavements due to use of improved construction quality. | Longer pavement life with fewer disruptions due to M&R activities. |
| Use material transfer vehicles. | May increase contract costs due to capital investments in equipment. | Reduced environmental impact through improved material quality and longer pavement service life. | ||
| Ensure proper handling of materials during transportation, placement, and compaction. | No cost associated with this approach. | Reduced environmental impact through improved material quality and longer pavement service life. | ||
| Construct Effective Longitudinal Joints | Avoid segregation during transportation and placement. | No cost associated with this approach. | Reduced environmental impact through improved material quality and resulting longer pavement service life. | Improved ride quality and longer pavement service life with fewer disruptions due to M&R activities. |
| Use adhesives or sealant overbanding. | May increase contract costs. | Reduced environmental impact with improved performance and longer life (fewer M&R activities, less frequent reconstruction). | ||
| Use proper compaction effort to achieve joint density. | No cost associated with this approach. | Reduced environmental impact through improved construction quality and resulting longer pavement service life. | ||
| Achieve Target Smoothness Requirements | Use proper placement and compaction techniques. | No cost associated with this approach | Reduced environmental impact through reduced fuel consumption during use phase. | Improved ride quality and longer pavement service life with fewer disruptions due to M&R activities. |
| Use Innovative Contracting Alternatives | Implement multi-parameter bidding systems (i.e., A+B+C). | May increase contract costs due to consideration of time to complete projects and environmental impact. | Reduced environmental impact because successful bid will reflect a combination of accelerated construction and techniques that directly reduce environmental impact. | Potential for reduced traffic delays. |
| Incentivize equipment improvements. | No additional agency costs if federal grants or tax reduction incentives are in place. | Potential for reductions in air pollutants and greenhouse gas emissions. | Potential for improvements in local air quality during construction. |
| Objectives | Approach for Improving Sustainability | Economic Impact | Environmental Impact | Societal Impact |
|---|---|---|---|---|
| Protect Water Resources | Collect and reuse concrete wash water. | Increased cost for wash water collection and processing, but reduced costs for fresh water and for remediation and clearing drains. | Positive impact by eliminating localized vegetation kills and pH impact on local surface waters. | Negligible to slightly positive impact. |
| Reduce Use of Virgin Materials | Use on-site recycling. | Reduced haul costs, reduced material costs. | Reduced fuel consumption, reduced GHGs, reduced consumption of resources. | Negligible to slightly positive impact. |
| Use two-lift paving. | Negligible to slightly higher construction costs. | More energy consumed in construction, improved use of local and recycled materials, potential reductions in use-phase fuel consumption and GHGs. | ||
| Improve Initial Ride Quality (Minimize Use- Phase Fuel Consumption and Emissions) | Use two-lift paving. | Negligible to slightly higher construction costs. | More energy consumed in construction, improved use of local and recycled materials, potential reductions in use-phase fuel consumption and GHGs. | Positive impact of improved ride quality, reduced use-phase costs for vehicles. |
| Use real-time profile measurement. | Capital cost of equipment may be reflected in bid prices. | Potential reductions in use-phase fuel consumption and GHGs. | Positive impact of improved ride quality, reduced use-phase costs for vehicles. | |
| Increase Pavement Service Life | Improve construction QA (including measurement of dowel alignment and location). | Additional testing costs. | Reduced environmental impact with improved performance and longer life (fewer M&R activities, less frequent reconstruction). | Potential for extended time between disruptions for M&R activities, less frequent reconstruction. |
| Use better curing materials and practices. | Negligible to modest increase in construction costs. | |||
| Balance Surface Friction and Tire-Pavement Noise | Properly select and design surface texture. | Negligible to modest increase in construction costs (depending upon surface texture selected). | Potential to reduce tire-pavement noise inside and outside of vehicles. | Potential for improvements in safety and reductions in noise (inside and outside of vehicle). |
| Minimize Construction Fuel Use and Emissions | Use on-site recycling for foundation layers. | Reduced haul costs, reduced material costs. | Reduced fuel consumption, reduced GHGs, reduced consumption of resources. | Negligible to slightly positive impact with reduction of congestion due to haul traffic. |
| Match construction equipment and production capacities. | Cost savings through more efficient equipment use. | Reduced fuel consumption and GHGs, less wasted material. | Minor impact. | |
| Use single-lift construction of concrete. | Cost savings over multi-lift construction processes. | Lower fuel consumption and GHG emissions during construction. | Negligible to favorable impact, depending upon time savings. | |
| Use roller-compacted concrete. | Significant construction cost savings (mainly due to more economical materials) | Lower fuel consumption and GHG emissions in construction. | Minimal impact for low-speed pavements; generally inadequate ride quality (without overlay or diamond grinding) for high-speed roadways. | |
| Use early-entry saws. | Reduced construction cost. | Reduced construction fuel consumption and GHG emissions. | Negligible. |