Bituminous Surface Treatment Research Articles

Verificación del diseño de tratamientos superficiales mediante el método MODOT T 72 y la sección 409 del Estado de Missouri y su posible incorporación a la normativa argentina

El presente artículo tiene por objeto observar la relación entre las especificaciones citadas en el Departamento de Transporte de Materiales de Construcción del Estado de Missouri, Estados Unidos “Test Method MoDOT T 72 Sweep Test of Bituminous Surface Treatment Simple” y la Sección 409 “Seal Coat” con las especificaciones establecidas en el Pliego de la Dirección Nacional de Vialidad de la República Argentina, considerando además adecuaciones surgidas en el LEMaC, a efectos de lograr mayor representatividad en relación a la obra. Para llevar a cabo la correlación de lo citado, se diseñó un tratamiento superficial simple con el método de dosificación propuesto por el Ing. Tagle, conocido como la Regla de 9-5-3 y una capa de sello con arena de trituración. Al tratamiento se lo somete al ensayo de barrido, y teniendo en cuenta los valores citados en la Sección 409 del MoDOT, se desea valorar la eficiencia del método de dosificación optado. Se analizaron los resultados obtenidos y se comparó si el método de dosificación con lo estipulado por la Sección 409 de acuerdo a la granulometría de la capa de sellado y las pérdidas derivadas del ensayo. En las Especificaciones Nacionales no existe una restricción numérica de dichas pérdidas sino solo la experiencia de obra y los resultados de ensayos cuando el tratamiento ya está colocado como lisura superficial, rugosidad y coeficiente de fricción, además de los parámetros de los materiales separadamente. Se ha logrado con la experimentación analizada, establecer una recomendación para su posible incorporación a los Pliegos citados.

Bituminous Surface Treatment Protocol for the Washington State Department of Transportation

To help the Washington State Department of Transportation (WSDOT) enhance its pavement preservation program through an improved understanding of the use of bituminous surface treatment (BST), the Highway Development and Management System was used as an analytical tool to test the average annual daily traffic and equivalent single-axle load levels appropriate as criteria for selecting the application of BST resurfacings to WSDOT pavements. It verified the feasibility of using BSTs to maintain pavements with higher traffic levels than have been applied in the past. Results also suggested that alternating the application of BST resurfacings and 45-mm hot-mix asphalt overlays is an effective rehabilitation strategy. Finally, the study results were used to estimate the impacts that increased use of BST surfaces would have on the performance of the state-owned route system.

Development of an Economic and Practical Alternative to Traditional Bituminous Surface Treatments

In many developing countries, a substantial portion of the road network, typically more than 75%, consists of earth and gravel roads that carry relatively low volumes of traffic. Traditionally, natural gravel materials are used for providing, maintaining, and upgrading such roads. However, most natural gravels have practical limitations on their use—for example, steep gradients and high rainfall, dust generation in dry weather, and slippery surfaces in wet weather. In addition, there is an increasing scarcity of suitable materials, and, moreover, maintenance is seldom carried out effectively in most developing countries. The inherent problems of maintaining unpaved roads can be overcome by paving them. However, even when this solution is economically justifiable, often it is not adopted widely in developing countries because of limited funds. However, a type of surfacing that can provide an economic and practical alternative to traditional surfacings and, by so doing, make better use of limited funds is the graded aggregate (Otta) seal. Otta seal surfacing is presented as an economic and practical alternative to the more traditional bituminous surface treatments, such as chip seals and slurry seals. The origin, properties, design, and construction of the Otta seal are outlined. The effects of its implementation and the various factors that contribute to its sustainability are discussed, and information is provided on global use of the Otta seal, including a case history relating to its introduction in southern Africa.

Performance Evaluation of Bituminous Surface Treatment Using Third-Scale Model Mobile Loading Simulator

This paper presents a new test protocol for the performance evaluation of bituminous surface treatments (BSTs) using the third-scale Model Mobile Loading Simulator (MMLS3). The BST performance characteristics covered by this protocol include aggregate retention, bleeding, skid resistance, aggregate embedment depth, cracking, and rutting. In this study, the new MMLS3 BST performance test method was applied to evaluate effects of various mix parameters on aggregate retention and bleeding; these parameters include aggregate and emulsion application rates, fines content, and aggregate gradation. Results demonstrate that the BST performance test method developed in this study is an excellent means of supporting current BST design and evaluating effects of various factors on performance of BSTs.

Performance Evaluation of Bituminous Surface Treatment Using Third-Scale Model Mobile Loading Simulator

This paper presents a new test protocol for the performance evaluation of bituminous surface treatments (BSTs) using the third-scale Model Mobile Loading Simulator (MMLS3). The BST performance characteristics covered by this protocol include aggregate retention, bleeding, skid resistance, aggregate embedment depth, cracking, and rutting. In this study, the new MMLS3 BST performance test method was applied to evaluate effects of various mix parameters on aggregate retention and bleeding; these parameters include aggregate and emulsion application rates, fines content, and aggregate gradation. Results demonstrate that the BST performance test method developed in this study is an excellent means of supporting current BST design and evaluating effects of various factors on performance of BSTs.

Stabilization Techniques for Unpaved Roads

An amendment to Virginia House Bill 1400, Item 490, No. 1h, calls for the Virginia Transportation Research Council to “continue its evaluation of soil stabilizers as an alternative to paving low-volume secondary roads.” In response, promising soil stabilization products were evaluated with the relatively new technique of deeply mixing chemical additives into unpaved roadbeds. This work is based on the construction of a 1.75-m-long trial installation on Old Wheatland Road in Loudoun County, where seven commercially available stabilization products were applied to the unpaved road. A rigorous evaluation of treatment performance will provide the basis for recommendations to the Virginia Department of Transportation's operating divisions regarding improvements to the maintenance practices for gravel roads. Results thus far indicate that the introduction of soil stabilizers through deep mixing is a promising technique. The life-cycle cost analysis indicates that constructing a standard bituminous surface-treated roadway and maintaining it as such is much more cost-effective than using any of the products in this trial. Further, the analysis indicates that using the bituminous surface treatment alternative is also much more cost-effective than maintaining an unpaved road.

Granular Overlays on Low-Volume Roads in Washington State: Structural and Performance Characteristics

The granular overlay system is an alternative type of overlay for rehabilitating mostly low-volume, rural pavements. The overlay consists of a layer of densely compacted, crushed stone overlaid by a generally thin surface layer (either a bituminous surface treatment or asphalt concrete). The Washington State Department of Transportation continues to be interested in these roadways because performance has been better than expected with rehabilitation survival lives doubling from 7 to 14 years with the addition of granular overlays. Previous attempts to backcalculate layer moduli and understand the structural characteristics of granular overlays were limited because of uncertainties associated with layer thicknesses. With known layer thicknesses obtained from four sites, backcalculation of granular overlay pavements was possible. These moduli along with straightforward performance information are used to characterize granular overlays.

Lessons Learned from the Failure of a Bituminous Surface Treatment in Central Oregon

During October 1996 a 10-km-long, double-lane, two-layer bituminous surface treatment (BST) was constructed near Bend, Oregon. The bottom BST layer consisted of an application of rapid setting high float emulsion (HFRS-2) followed by an application of 19- to 12.5-mm chips. The top layer consisted of various emulsions and 13- to 6.3-mm chips. Soon after construction up to 20 large commercial timber hauling trucks per day used the road during the wettest November and December in over 20 years. By the end of December 1996 most of the top layer of chips had disappeared, large numbers of potholes had developed, and the emulsion was not adhering to the bottom layer of chips. Failure resulted from interacting factors including a dust coating on the chips, an incompatibility of emulsion and chips, cold and wet weather, and a nearly impervious base course. The following lessons were learned from this project: ( a) An adequate and accurate quality control and quality assurance plan should be in place before construction. ( b) In wet environments, base courses under a BST should be free draining. ( c) Either cool and humid construction weather or dust coatings on the aggregate may not lead to failure, but in concert they raise the potential for failure dramatically. ( d) Not all emulsions are manufactured the same. An emulsion’s break and cure time may vary depending on the emulsion’s additives. ( e) The asphalt emulsion and aggregate must be compatible with each other at conditions expected on the road surface.

Bituminous surface treatment and its effectiveness as a municipal road surface—Faro, Yukon

The use of bituminous surface treatment (BST) as a road surface is a technique commonly accepted and understood by most provincial and territorial highways departments, but for the average engineer or municipality, it may be nothing more than the squirting of some oil on a road surface and covering this oil with some gravel.The topic of BST construction brings with it many different approaches, applications, and techniques. In the Yukon, Alaska, and western Canada, the two basic techniques used are: rapid setting emulsions and chip aggregates or high float emulsions and well-graded aggregates.Before the right approach is arrived at, an analysis of the expected traffic volumes, the condition of the sub-base, the quality and quantity of aggregate available, the types of emulsions available, and the cost of installing either of the techniques should be undertaken.In 1981, the town of Faro hired a local Whitehorse contractor to single surface treat 4.5 km of local roads, the final result being a combination of pot holes, ravelling, and streaking. A detailed investigation was undertaken to determine why the problems were experienced and to ascertain whether BST should be used on municipal streets in the future.The research indicated that the general design principles were correct but that an overabundance of gravel being specified, coupled with numerous errors in construction, produced an inferior product.A second treatment of approximately 1.5 km of road was undertaken in 1982 by a more experienced applicator, namely, the Yukon Government Highways forces, and many of the problems experienced in 1981 were overcome.The purpose of this paper is to present both the problems experienced in Faro and what approaches, applications, and techniques should be followed to minimize the possibility of these problems occurring in the future. Key words: aggregate, asphalt emulsion, tack coat, sub-base, bituminous, soil cement, streaking, pneumatic.