Characteristics of a Surfactant Produced Warm Mix Asphalt Binder and Workability of the Mixture

Warm mix asphalt (WMA) technologies significantly reduced the mixing and compaction temperatures in the construction of asphalt pavement, which thus lowered the energy consumption and gas emissions. Different types of WMA additives have been developed and applied in the past decade. However, there are still several concerns associated with the application of WMA technologies. The objective of this study was to address the characteristics of WMA binder produced using a surfactant additive namely, ADDITIVE-A. Two binders, 70 penetration grade (70#) asphalt and 90 penetration grade (90#) asphalt were applied as the base binder to produce the WMA in this study. A portable workability device was presented in this paper to evaluate the torque values of WMAs since the workability is the main property to determine the mixing and compaction temperatures of WMA and a laboratory workability test has yet to be developed. The proper mixing and compaction temperatures were also obtained based on the proposed test. A series of tests, including penetration, softening point, ductility and viscosity of different WMA additive concentrations (0, 0.3, 0.5, 0.7, and 0.9 % by the weight of asphalt binder) were conducted to investigate the mechanisms of the surfactant on asphalt binder. The contact angles of WMA binders were tested to investigate the modification mechanism of surfactant additive on asphalt binder. The laboratory tests indicate that the surfactant additive (ADDITIVE-A) makes the asphalt binder softer, more temperature sensitive, and having better low temperature property. However, the surfactant does not show a significant impact on the high temperature property and viscosity. The addition of the surfactant additive increased the workability of asphalt mixture and decreased the mixing and compaction temperatures of asphalt mixture. Based on the workability test results, the 0.7 % concentrations of the ADDITIVE-A provided a more obvious effect to reduce the production temperature of asphalt mixture

A Bitumen-Based Prototype to Predict the Workability of Asphalt Concrete Mixtures

Having a reliable and repeatable method for measuring the workability of asphalt mixtures for a wide range of asphalt blends is important. The major objective of this paper is to develop a new bitumen-based prototype for the measurement of the workability of different asphalt blends. Correlation and prediction of the mixing temperature with the aid of the developed prototype have been established as a secondary objective of this study. At first, a principle was presented as a basis to develop the workability prototype. The device developed in this study utilized a commercially available motorized Vane Shear Test (VST) apparatus which is mainly used to measure the shear strength of soil. To resemble the aggregate effect while mixing, a specially designed spindle was developed. The VST has been modified to suit the present purpose of the workability test. An accurate torque meter was installed to measure the torque required to rotate the spindle in the blend at a constant revolution. The device was tested with asphalt blends of different ranges of workability. The workabilities of polymer-modified and water-foamed asphalts were evaluated at temperatures of 100, 140 and 180 °C, respectively. It was found that the bitumen-based prototype was able to differentiate the workability in light of the constituents of the studied blends. In addition, the prototype helped in roughly predicting the mixing temperatures of the studied blends based on the concept of Workability Index (WI)