Engineers use flexible pavements as layered structures to help distribute traffic loads. Flexible pavements consist of a surface layer, such as asphalt concrete, over a base layer and subbase layer. This technology can be used on various types of road construction, including sealed and unsealed roads. Stabilizers can be employed to improve the mechanical properties of the unbound aggregate surface layer and are important when factoring for load distribution.
Additives can also be incorporated to help with stabilization of the aggregate materials and for dust control. There isn’t a widely recognized method for ranking the different additives, and so the authors of this study focused on evaluating the effectiveness of stabilization technologies in stabilizing coarse-graded aggregates. With an eye on boosting confidence among road authorities and stakeholders, Diego Maria Barbieri, Baowen Lou, Robert Jason Dyke, Hao Chen, Fusong Wang, Berthe Dongmo-Engeland, Jeb S. Tingle, and Inge Hoff, performed laboratory-based research using three different testing and analysis techniques.
In their study, “Stabilization of Coarse Aggregates with Traditional and Nontraditional Additives” in the Journal of Materials in Civil Engineering, the authors systematically evaluated the performance of different stabilization technologies, evaluating the stiffness and the development of permanent deformation of the stabilized materials. They also assessed the stripping potential for each additive and performed microscope analysis to examine the coated aggregate surface. Learn more about stabilizing coarse aggregates at https://doi.org/10.1061/(ASCE)MT.1943-5533.0004406. The abstract is below.
Abstract
High-quality coarse aggregates are routinely used for the surface, base, and subbase layers in paved roads or the surface course in unpaved low-volume roads. Unfortunately, high-quality aggregates meeting stringent material specifications are becoming increasingly costly and difficult to find within reasonable distances of road construction projects. Various stabilization technologies can be employed to improve the mechanical properties of available aggregate materials, providing environmental and economic benefits. This investigation used three laboratory test methods to evaluate and compare all the existing kinds of additive technologies suitable to stabilize a coarse-graded road unbound layer. Two traditional solutions (cement and bitumen) and eleven nontraditional solutions (categorized as either brine salts, clay binders, organic nonpetroleum products, organic petroleum products, or synthetic polymers) were included. Repeated load triaxial tests were performed to evaluate the dynamic behavior of the untreated and treated aggregates in terms of their resilient modulus and the resistance against permanent deformation. A modified version of the rolling bottle test was used to appraise the stripping resistance offered by each additive. A microscopic analysis was conducted to visually evaluate the propensity of the additives to adequately coat the surface of the aggregates. All the stabilization technologies improved the material stiffness, with the most significant improvements produced by calcium chloride salt, bentonite, lignosulfonate, and cement mixed with a mineral mixture. The stabilization additives effectively reduced permanent deformations, except for the specimens stabilized with polyurethane and bitumen. Finally, the polymer-based additives and bitumen demonstrated very good resistance to stripping, with polyurethane providing the smallest mass loss. This study documents that nontraditional stabilization technologies can provide effective alternatives to the traditional stabilizers and documents that a “one-size-fits-all” additive agent is unlikely to be developed.
Read the paper in full in the ASCE Library: https://doi.org/10.1061/(ASCE)MT.1943-5533.0004406
