Technical Paper ISSN 1997-1400 Int. J. Pavement Res. Technol. 6(5):562-569 Copyright @ Chinese Society of Pavement Engineering 562 International Journal of Pavement Research and Technology Vol.6 No.5 Sep. 2013 Warm Mix Asphalt with Synthetic Zeolite: a Laboratory Study on Mixes Workability Rosolino Vaiana 1 , Teresa Iuele 1+ , and Vincenzo Gallelli 1 ─────────────────────────────────────────────────────── Abstract: In recent years, several warm mix asphalt technologies have been developed in order to enable significant energy savings and harmful emissions restraint by reducing mixing and compaction temperatures in hot mix asphalt production processes. This paper focuses on the evaluation of workability of WMA produced in laboratory by water-containing methodology with the addition of synthetic zeolite. Both volumetric and mechanical performance of warm asphalt mixtures compared with those of a reference hot mix were evaluated. For the Marshall specimens the variation of density with the compaction energy was also investigated. Finally, some considerations about the effect of the time of foaming (between mixing and compaction) on mixes workability are drawn. DOI:10.6135/ijprt.org.tw/2013.6(5).562 Key words: Asphalt workability; Compaction energy; Foaming process; Synthetic zeolite; Warm mix asphalt. ─────────────────────────────────────────────────────── Introduction 12 The objectives of preserving the environmental quality, reducing the use of natural resources and protecting human health, are fundamental in the aim of promoting the sustainable development. Industrial activities produce the highest contribute to the greenhouse effects; for this reason the asphalt paving industry has continually strived to recycle more asphalt and to reduce emissions in order to become a more environment friendly industry [1-4]. The primary sources of emissions in an asphalt plant are the mixers, dryers, and hot bins, which emit particulate matter, such as dust, smoke, exhaust vapor, and other gaseous pollutants. Some other sources are the storage silos, truck loading operations, binder storage tanks, conveyers, stockpiles, etc. At the same time, the risk for the health of the workforce from asphalt fumes due to an excessive exposure during laying operations is high [5]. The bulk of CO 2 , SO 2 and NO x emissions from asphalt pavements happen during the initial construction, because of the high temperature required for mixing and paving [5]. Moreover, the whole process of asphalt mix production determines considerable energy consumption due to the high temperature reached in asphalt plants. That said, it is clear the need to develop innovative technology solutions in the asphalt industry that enable significant energy savings and a large emissions restraint by reducing mixing and compaction temperatures and maintaining, at the same time, high levels of performance without affecting the mechanical and functional properties of the mix [6-10]. In the last years, several new processes that reduce the usual temperature levels for Hot Mix Asphalt (HMA) have been developed [5, 11-12]. These technologies are referred to as Warm Mix Asphalt (WMA), an emerging class of asphalt mixture that reduces heating requirements during production and compaction operations. Several WMA technologies, based on different 1 Department of Civil Engineering, University of Calabria, 87036 - Rende, Cosenza, Italy. + Corresponding Author: E-mail teresa.iuele@unical.it Note: Submitted January 15, 2013; Revised June 4, 2013; Accepted June 5, 2013. production processes, are been widespread worldwide. A brief description of them is reported in the subsequent section. Warm Mix Asphalt Technologies. WMA requires lower production and compaction temperatures if compared to HMA while aiming to maintain the desired performance. This spread is estimated between about 20 and 50°C, depending on the adopted technology [5-13]. WMA technologies are frequently classified by the methodology used to improve asphalt concrete workability [5-13]. In particular, two main categories can be identified as follows (see Fig. 1): (i) foaming processes; (ii) addition of dopes. The foaming process is characterized by the injection of small amounts of water directly into the mix chamber or into the hot binder; in fact, when the water is dispersed in hot asphalt, it vaporizes (from contact with the hot asphalt) and it results in a binder expansion with a consequent reduction of the mix viscosity [14]. This process can be reached by means of the following sub-methodologies:  Water-containing: this method uses synthetic zeolite to produce the foaming process. This type of additive is composed of aluminosilicates of alkali metals, and has been hydro-thermally crystallized. Zeolite’s structure has large and interconnected spaces, which can accommodate a wide variety of cations (Na + , K + , Ca 2+ , Mg 2+ ) and even molecules such as water. The spaces are interconnected and form long wide channels of varying sizes depending on the mineral. These channels allow the easy movement of the resident ions and molecules into and out of the structure. In particular, this absorption and desorption process through the zeolite interconnected cavities does not damage the crystal structure. When the temperature goes up over 80-90° C, zeolite structure releases the water crystallized, making the foaming effect to be reached [11, 13, 15].  Water-based: this technology uses special nozzles to produce the foaming effect, injecting directly water under pressure into the hot binder flow. The water evaporation produces a large