Develop a Study for Geosynthetic Materials for Use in Reducing Pavement Section Thickness

P227-21-803Geosynthetics have been used to reinforce aggregate base courses to increase the structural support from the base to the pavement structure. This project aims to develop a study framework to evaluate and quantify the structural benefits under Nevada conditions. To achieve this objective, a five-stage research plan was developed to support a controlled field demonstration, with input regarding design, specification, and standards. This report provides a methodology to determine the expected design life of a specific site with known climate characteristics, subgrade modulus, and traffic. Included are recommendations for the pavement design, testing layout, testing plan, construction guidelines, preliminary implementation plan, and cost estimate

Rheological Properties of Modified Crumb Rubber Asphalt Binder and Selecting the Best Modified Binder Using AHP Method

Crumb rubber modifier (CRM) is one of the most popular asphalt binder modifiers due to the economic benefits and desired physical and rheological properties of asphalt binders and asphalt mixes. This research focuses on evaluating the properties of rubber-modified asphalt binders and selecting the best modified binder. The modified binders were produced by blending virgin binders with CRM at various contents of different gradations, and different methods of grinding. CRM made through ambient and cryogenic grinding methods with two gradation sizes were produced and tested. Three different virgin binders from two sources were obtained and used. The Analytic Hierarchy Process (AHP) method was used to determine the best combination of virgin binder and CRM, based on the rheological properties and their importance in Nevada’s construction code. Based on AHP analysis, ambient CRM obtained the highest priority. CRM contents of 10% and 15% were ranked higher than 20% depending on the grade of the virgin binder. Both mesh 20 and 40 CRM sizes were favorable

Toughness, Tenacity and Maximum Initial Strength of Rubber Modified Asphalt Binders

The toughness and tenacity test method, which was developed in the 1980s, is popular for evaluating a polymermodified binder. Several states like Nevada require performing this test to evaluate non-modified binder samples, as well as other types of modified binders. In this regard, a toughness and tenacity test was performed on rubber-modified samples produced from virgin binder PG58-28, PG64-16 and AC-20. In order to take the rubber size, type and content into account, two rubber sizes, mesh #20 and #40, two rubber types, ambient and cryogenic, and three rubber contents, 10%, 15%, and 20% were produced and tested. The results then were compared with polymer-modified and terminally blended rubber-modified samples. The results show improvement in the amount of initial maximum strength, and a decline in the magnitude of elongation, toughness and tenacity for the rubber-modified binder, compared to other types of binders

Design and Preliminary Testing of Demand-Responsive Transverse Rumble Strips

Transverse rumble strips are common practice to alert drivers by engaging their auditory and tactile senses in addition to visual senses by traffic signals. However, continuous exposure to noise and vibration by transverse rumble strips often results in diminished effectiveness and erratic behaviors, leading to additional safety challenges. In response, demand-responsive transverse rumble strips were developed as traffic safety countermeasures that reduce unnecessary noise and vibration associated with transverse rumble strips by incorporating active control of the rumble strips. Rather than staying static, demand-responsive transverse rumble strips are activated based on the presence of pedestrians, at predesignated times, or in response to abrupt changes in traffic flow. To evaluate the effectiveness of demand-responsive transverse rumble strips, the research team assessed noise and vibration data, both inside the vehicles and on the roadside, for various types of vehicles traveling at different speeds. The test data indicate that demand-responsive transverse rumble strips produced noticeable in-vehicle noise and vibration that could alert drivers to downstream events. Furthermore, demand-responsive transverse rumble strips generated sufficient noise to alert roadside pedestrians to vehicle presence but at low enough level to be considered as acceptable for a residential neighborhood use. Accordingly, demand-responsive transverse rumble strips could address the challenges that static transverse rumble strips face, by providing a design with relatively limited noise while enhancing safety

Green Up Pavement Rehabilitation Design Tool

While designers produce pavement rehabilitation recommendations every day, for projects of all sizes, most designers have little information on the environmental impact of their recommendations. This research developed a new decision tool, called the “Green Up Pavement Rehabilitation Design Tool,” to allow the comparison of different rehabilitation solutions in terms of greenhouse gas emissions and to encourage sustainable practices such as materials recycling and the use of permeable, cool, and quiet pavement surfaces. The project aligns with the major goal of California Senate Bill 1, which is “to address deferred maintenance on the state highway system and the local street and road system,” by providing a rehabilitation strategy selection tool as well as an educational tool to promote sustainable pavement practices. The Green Up graphic and the overall methodology were finalized in consultation with representatives of the portland cement concrete and asphalt industries in California. For designers interested in learning more, the tool includes fact sheets about sustainable pavement rehabilitation strategies and links to additional online resources

Bio-based Renewable Additives for Anti-icing Applications (Phase I)

The performance and impacts of several bio-based anti-icers along with a traditional chloride-based anti-icer (salt brine) were evaluated. A statistical design of experiments (uniform design) was employed for developing anti-icing liquids consisting of cost-competitive chemicals such as bio-based compounds (e.g., sugar beet extract and dandelion extract), rock salt, sodium metasilicate, and sodium formate. The following experimentally obtained parameters were examined as a function of the formulation design: ice-melting capacity and ice penetration at 25°F (−3.9°C) and 15°F (−9.4°C), compressive strength of Portland cement mortar samples after 10 freezethaw/deicer cycles, corrosion rate of C1010 carbon steel after 24-hour immersion, and impact on asphalt binder’s stiffness. One viable formula (“best performer”) was tested for freezing point depression phase diagram (ASTM D1177-88) and the friction coefficient of asphalt pavement treated by this anti-icing formulation (vs. 23 wt.% NaCl) at a certain temperature near 25°F or 30°F after being applied at 30 gallons per lane mile (1 hour after simulated trafficking and plowing). Laboratory data shed light on the selection and formulation of innovative bio-based snow and ice control chemicals that can significantly reduce the costs of winter maintenance operations. This exploratory investigation contributes to more systematic study of optimizing “greener” anti-icers using renewable resources

Evaluation of the Properties of Rubberized Asphalt Binders and Mixtures

Rubber modified binder samples are tested and evaluated based on SHRP requirements. Best rubber content is suggested for modifying binder. Rubber modified asphalt mixtures were manufactured and tested. Based on Hveem stability and volumetric properties of asphalt mixtures, optimum binder content is evaluated and reported. Performance properties of asphalt mixtures made with various rubber size and method were analyzed and compared. An ultrasound measurement performed on asphalt mixture samples and the results were analyzed. It is discovered that rubber improves asphalt viscosity and resistance to rutting deformation. Rubber also increases asphalt’s dynamic modulus

Impact of Curling and Warping on Concrete Pavement

Portland cement concrete (PCC) pavement undergoes repeated environmental load-related deflection resulting from temperature and moisture variations across the pavement depth. This phenomenon, referred to as PCC pavement curling and warping, has been known and studied since the mid-1920s. Slab curvature can be further magnified under repeated traffic loads and may ultimately lead to fatigue failures, including top-down and bottom-up transverse, longitudinal, and corner cracking. It is therefore important to measure the “true” degree of curling and warping in PCC pavements, not only for quality control (QC) and quality assurance (QA) purposes, but also to achieve a better understanding of its relationship to long-term pavement performance. In order to better understand the curling and warping behavior of PCC pavements in Iowa and provide recommendations to mitigate curling and warping deflections, field investigations were performed at six existing sites during the late fall of 2015. These sites included PCC pavements with various ages, slab shapes, mix design aspects, and environmental conditions during construction. A stationary light detection and ranging (LiDAR) device was used to scan the slab surfaces. The degree of curling and warping along the longitudinal, transverse, and diagonal directions was calculated for the selected slabs based on the point clouds acquired using LiDAR. The results and findings are correlated to variations in pavement performance, mix design, pavement design, and construction details at each site. Recommendations regarding how to minimize curling and warping are provided based on a literature review and this field study. Some examples of using point cloud data to build three-dimensional (3D) models of the overall curvature of the slab shape are presented to show the feasibility of using this 3D analysis method for curling and warping analysis

Recycling toward sustainable pavement development: End-of-life considerations in asphalt pavement

As quality aggregate sources are depleted, there is a growing importance given to incorporating recycled co-products and waste materials (RCWMs) in new and rehabilitated pavements. An ideal goal would be using recycled materials to create long-lived, well-performing pavement and then being able to use those materials again at the end of their life to create new pavement, thereby effectively achieving a zerowaste highway construction stream. This would not only produce distinct cost advantages, but it would also significantly reduce energy consumption and greenhouse gas (GHG) emissions and eliminate the need for landfill disposal. Drawing from ISO standards and practices, this article reviews the recycling methods and definitions associated with the End-of-Life (EOL) phase and present various EOL considerations for asphalt pavements and the associated challenges to quantify EOL contribution in the pavement life cycle