Greenhouse Gas Emissions from Hot and Warm Mix Asphalt with Cup Lump Rubber and Palm Oil Fuel Ash: Toward Low-Emission Pavement Solutions

The hot mix asphalt (HMA) production consumes a lot of energy, which in turn generates a large carbon footprint. This study examined the environmental impact of warm mix asphalt (WMA) incorporated with Cup Lump Rubber (CLR), Evotherm additive (EVO), and Palm Oil Fuel Ash (POFA), which are all eco-friendly materials. Four asphalt mixtures were studied: (i) Neat Bitumen (NB), (ii) NB + CLR, (iii) NB + CLR + EVO, (iv) NB + CLR + EVO + POFA. The mixtures were prepared in a lab under standard temperature, and real-time gas emissions were measured (O2, CO2, NO2, SO2, NOn) in a 300-s mixing time. The highest CO2 (1.78 kg/ton) and SO2 (0.48 g/ton) emissions were recorded at high temperatures of 180 °C for NB + CLR. NO2 and SO2 emissions were reduced through Evotherm, and when POFA was used for further modification, SO2 was reduced by an additional 33.2%. These improvements are attributed to lower production temperatures and POFA’s pozzolanic interaction, which neutralizes acid gases. The combined use of WMA technology and waste-derived additives provides a practical route to low-emission asphalt production.