The implementation of geopolymer as an additive of warm-mix asphalt to reduce emissions

The vast revolution of highways and roads infrastructures has shaped the high demand for bitumen production which raised several concerns related to its environmental impact. This paper proposes the use of geopolymer as an additive of warm-mix asphalt (WMA) with the aim of reducing harmful emissions companioned with asphalt production. Two types of geopolymer additive were assessed in this study including original geopolymer (G) and anhydrous geopolymer (AG). The effect of geopolymer addition on the conventional properties of bitumen was evaluated through softening point and penetration according to the Chinese standard JTG-E20-2011, besides SARA components (saturates, aromatics, resins, and asphaltenes, i.e. SARA) and fourier transform infrared spectroscopy (FTIR) analyses. The pore structure of geopolymer additive was identified using nitrogen adsorption-desorption measurements. Thermogravimetry coupled with mass spectrometry (TG-MS) and particulate matter (PM) test were conducted to study the inhabitation effect of geopolymer additives on absorbing different volatile products. It was found that the bitumen maintained its conventional properties after the addition of geopolymer at which softening point, penetration, SARA and FTIR results showed no significant changes. The N2 adsorption results revealed that the geopolymer additive is highly pours comprising plate-like pores network with several slit-shaped mesopores since the bulk of pores in the geopolymer was smaller than 50 nm. Such pours microstructure equipped the geopolymer additives with high absorption capacity that could be beneficial in reducing the volatile organic compounds (VOCs) during bitumen production. The TG-MS and PM emissions results confirmed the high capability of geopolymer additives to inhibit toxic emissions during asphalt production. The addition of 6% geopolymer by weight was able to cut the bitumen’s VOCs by up to 50% and delay the escape of PM significantly. Such approach confirms that geopolymer modified WMA exhibits improved performance with lower cost via saving energy and reducing PM & VOCs emissions relative to the conventional production methods.