Sensitivity of Nozzle-Based Foamed Asphalt Binder Characteristics to Foaming Parameters

Foam-based warm-mix asphalt technologies decrease the overall viscosity of the asphalt mixture at lower temperatures so that it is workable during construction. However, after construction, viscosity increases rapidly as the foam disappears and the temperature drops. Although the production of the foamed binder is a relatively simple process, in which hot binder is mixed with a limited amount of water (typically 1% to 3% by weight of the binder), the rheology of the foamed binder is complex. The characteristics of foamed binders depend on various factors such as the binder type, grade, and modification; the foaming technology used; amount of water; and temperature. This study investigated the sensitivity of the characteristics of foamed binders to parameters such as injected air pressure and water content. The foamed binder characteristics, including the expansion ratio, half-life, foam index, bubble size distribution, and surface area index, were measured with a novel automated laboratory device called the asphalt foam collapse test. The measurements were conducted in several conditions, including (a) constant water content and variable air pressure, (b) variable water content and constant air pressure, and (c) variable air pressure and water content. It was concluded that both water content and air pressure significantly affected foamed binder characteristics and their internal morphology.


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Foam-based Warm Mix Asphalt (WMA) technologies decrease the viscosity of the asphalt so that it is workable during construction. However, after construction, viscosity increases rapidly as the foam disappears and temperature drops. During the process of dissipation of foam, depending on the environmental conditions, the moisture may not escape and may be trapped inside the mixture. This trapped moisture can cause detrimental failures by breaking the adhesive bonds between the aggregates and the asphalt bind...
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Warm Mix Asphalt (WMA), the technology that allows significant reduction in the mixing and compaction temperatures of asphalt mixtures, has been commonly used globally since the early 2000s. This study evaluates the effect of compaction temperature (CT) on WMA and Hot Mix Asphalt (HMA) mixtures volumetrics, degradation, stability, and compactability properties. Although both Superpave Gyratory Compactor (SPGC) and Marshall hammer are used for sample preparation, the focus of this study is to develop compact...
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Citation Formats
H. I. Öztürk, “Sensitivity of Nozzle-Based Foamed Asphalt Binder Characteristics to Foaming Parameters,” TRANSPORTATION RESEARCH RECORD, pp. 120–129, 2014, Accessed: 00, 2020. [Online]. Available: