Studies of sustainable pavement maintenance: Waste management and innovative preservation materials

Sustainability is a concept focusing on environmental, social, and economic factors in decision-making processes. In recent years, more and more state highway agencies (SHAs) are embracing principles of sustainability in pavement design, construction, use, maintenance, and material production. A sustainable pavement system would not only meet the basic needs of traveling, but would remain effective and environmentally friendly during highway construction, service, and preservation. Efficient collection of pavement cracking data is essential to pavement sustainability because it aids in determining selection of optimum pavement preservation technology. While there are multiple methods for identification of pavement cracking data, some are not generally compatible, possibly complicating the sharing of cracking-data information among agencies and vendors and reporting such data to the US Federal Highway Administration (FHWA) for establishing national, state, and local performance goals. In this study, comprehensive review of existing federal and SHAs’ cracking data collection practices were conducted, including how data should be collected and classified. The study’s findings are summarized in the context of developing standard definitions for comparable pavement cracking data. To seek sustainability goals for concrete pavements, a concrete slurry waste, generated from common resurfacing rehabilitation activities known as diamond grinding, was evaluated. During grinding operations, a high pH slurry comprised of removed concrete and cooling water for blades, designated as concrete grinding residue (CGR), may be generated and discharged along the roadside, resulting in potentially critical environmental issues. To understand the effects of CGR on soil chemical properties, a field site was built for applying four different CGR rates: 2.24, 4.48, 6.72 and 8.96 kg/m2 (0, 10, 20, and 40 ton/acre), and measurements of soil pH, electrical conductivity (EC), alkalinity, cation exchange capacity (CEC), exchangeable sodium percentage (ESP), and percent base saturation (PBS) at the site were determined and statistically analyzed both before and after CGR application. The results indicated that CGR significantly impacted the chemical properties of soil, and this impact became greater with increase in CGR application rates. The results indicated that, while CGR can be discharged along roadsides at up to 8.96 kg/m2 (40 ton/acre), the CGR’s unreacted cement and high pH have potential for being reused to stabilize roadbed soil. To investigate reuse of CGR, this study mixed 10%, 20%, 30%, and 40% samples of CGR by weight with soil to stabilize two types of Iowa soils. Strength and penetration tests for CGR-treated soil showed that a 20% CGR addition was the optimum content in that it resulted in the greatest strength, and other laboratory testing results revealed that CGR treatment could reduce the maximum values of dry density and plasticity. Asphalt pavements can also be made sustainable by using innovative preservation methods. Fog seal is a commonly used pavement preservation technology that involves spraying petroleum-based emulsion on a road surface to maintain skid resistance, prevent oxidation and reduce water infiltration. In recent years, bio-based fog sealants have received increased attention in the United States, and RePLAY, a soy-based sealant derived from an agricultural agent, has been successfully used in some areas. To evaluate the effectiveness of RePLAY as an alternative for preserving Iowa roads, a 5.3 km (3.3 mile) long asphalt pavement section was selected for application of RePLAY followed by a two-year investigation of the pavement’s marking retroreflectivity, surface friction, water absorption, and air permeability. An untreated section and three treated sections using spray rates of 0.091, 0.113, and 0.136 l/m2 (0.020, 0.025, and 0.030 gal/yd2) were set up for this purpose, and field results showed that retroreflectivity and skid resistance decreases due to application of bio-sealant were restored to their original levels within two weeks and eleven months, respectively. The laboratory results revealed that the bio-sealant-treated specimens with the highest application rate exhibited the lowest water absorption and air permeability