Characterization Of Latex-Foamed Asphalt Binders And Mixtures With Different Foaming Agents

With constantly depressed global economic over the past year,the global exporter market of raw materials is tightening and the prices also goes down.Moreover,the exporter market becomes more dissipated due to the trade war from 2019 year.In this case,Malaysia,as a major exporter for latex,has accumulated a lot of excess capacity.The lowering of the costs of latex globally and its surplus production have interested the Malaysian government in exploiting the ‘resource’ in road construction and maintenance.Introducing latex as a modifier to asphalt binder can maximize the latex utilization rate and enhance the rheological characteristics of the asphalt binder.However,the addition of latex had also resulted in increased asphalt binder viscosity.The high asphalt viscosity is not preferable for the production of asphalt mixtures,and the viscosity should be lowered for optimum workability and better aggregate coating.Traditionally,the asphalt mixture production temperature is elevated for the purpose of reducing the viscosity of latex modified asphalt binder.At the same time,it would lead to excessive energy consumption and emission to the environment.Foaming asphalt as the most widely used technology among WMA(warm asphalt mixture)technologies is utilized to lower the production temperature of asphalt mixtures in this research.Traditional,the production of water foamed asphalt binder is that a designated amount of water is injected into hot asphalt binder under a high air pressure.To develop and evaluate the foaming process using potential physical foaming agent towards enhancing the WMA technology,Methanol as a physical foaming agent will be investigated in this study.This proposed research will-improve the cognition of the foaming process and enhances the performance of WMA to support the sustainable development.Methanol can function in the same manner as water but requires less energy to foam,due to its lower boiling point,65℃.The latent heat of vaporization and boiling point of water are in the region of approximately2260 k J/kg and 100℃,while the latent heat of vaporization and boiling point of methanol are approximately 1100 k J/kg and 65℃.These two criterions show that methanol is able to be an alternative foaming agent in the production of low emission asphalt.WMA pavement has potential to be produced at very low temperatures with methanol,perhaps as low as 80℃.Therefore,it is essential to understanding the effect and foamability of foaming agent a,the asphalt binder behaviour during foaming process and rheological properties of the foamed asphalt binders which is able to contribute on helping control the foam structure and predict the final performance of the foamed WMA.Furthermore,the moisture susceptibility of foaming WMA and HMA(hot asphalt mixture)also will be evaluated and compared in this study.For the purpose of understanding the overall performance of newly foamed WMA,this material will be evaluated for,service characteristics,mechanical performance,and moisture susceptibility during production and construction stages.The findings show that the presence of latex contributed to a higher softening point,viscosity,expansion ratio,elastic property,and rutting resistance ofasphalt binders.Also,the foaming agents(water or diluted methanol)decreased the viscosity and led to better workability and aggregate coating.The application of foaming agent(diluted methanol or water)improved the workability of asphalt mixtures.Moreover,the diluted methanol as a foaming agent illustrates better performance compared to water on foamed asphalt mixtures.