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

Abstract

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.

The characterisation of foamed asphalt cement using a rotational viscometer

“…There has been some research that attempts to quantify the foaming mechanisms of the asphalt binder. Ozturk and Kutay worked with an optical system to develop the surface area index (SAI) parameter, which aims to quantify the total surface area of the bubbles from PTI's foaming equipment (Ozturk and Kutay 2014). Similarly, Arega et al worked with a laser system to quantify unstable/short-life bubbles and semistable/long-life bubbles from Wirtgen's foaming equipment (Arega et al 2014).…”

Chemical and Foaming Analysis on Cold Mix Asphalt Performance with Recycled Asphalt Pavement

“…According to Ozturk et al, bubble size distribution plays a crucial role in determining the type of binder foam.. Image acquisition analysis was applied in various cases to understand better the foam expansion and collapse mechanism [19]. Besides the complicated foam parameters, Chemical characteristics on foam asphalt might affect the foamability.…”

Effect of curing condition on mechanical property of cold recycling mixture with foamed asphalt

“…KWEIR conducted an analysis on the foaming process of foamed asphalt, and then researched the influence factors of foamed asphalt mixture, including the initial water content, water quantity change and compaction energy, etc [9]. It can be found from the above research status at home and abroad, the influence study of curing condition on cold recycling mixture with foamed asphalt was not enough in-depth [10,11]. At present, the determination of curing condition was mainly based on engineering experience.…”