Reduce VOCs and PM emissions of warm-mix asphalt using geopolymer additives

Abstract

Volatile organic compounds (VOCs) and particulate matter (PM) emissions are usually the main concerns of asphalt industry. This study reports the experimental results of the inhibition effect of geopolymer additives when incorporated in bitumen with the intention of reducing VOCs and PM emissions. The pore structure of the geopolymer additives and their adsorption technique were assessed. The effectiveness of two types of geopolymer additives (i.e. original and anhydrous) was evaluated according to their impact on bitumen conventional properties (i.e. softening point, penetration, SARA components analysis, and FTIR spectra), VOCs reduction and PM emissions levels.According to thermogravimetry coupled with mass spectrometry (TG-MS) and particulate matter (PM) tests results, the addition of geopolymer reduced the VOCs and PM emissions during asphalt production, not only for warm mix asphalt (WMA) but also for hot mix asphalt (HMA). Such additives had no significant impact on bitumen’s conventional properties. Based on the nitrogen adsorption-desorption measurements, the adsorption mechanisms of geopolymer additives can be divided into three continuous phases: monolayer adsorption, multilayer adsorption, and capillary condensation. Further, the majority of the pores available in geopolymer additives were smaller than 50 nm (i.e. plate-like pores network with several slit-shaped mesopores) which entitled them with relatively high capability of absorbing the bitumen VOCs and PM Emissions.