Emission reduction effect of eco-friendly asphalt modified with isocyanate-nanoclay composites

The environmental and health issues associated with the generation of fumes during hot mix asphalt used in road construction necessitate the exploration of cleaner production methods. This study investigated the viability of utilizing isocyanate-nanoclay composites as modifiers for eco-friendly modified asphalt. The composite modified asphalt samples were prepared by adding isocyanate (isophorone diisocyanate, IPDI) and nanoclay (organic montmorillonite, OMMT or attapulgite, ATT) to the base asphalt at varying contents. A device for generating and collecting asphalt fumes was developed. The impact of modifier dosage on fume emission reduction was assessed quantitatively and qualitatively using ultraviolet-visible spectrophotometry and gas chromatography-mass spectrometry, yielding the optimal ratio of composite modifiers. The fume emission reduction mechanism of the modifiers was elucidated by analyzing changes in distribution, functional group composition and micromolecular spacing of asphalt using fluorescence microscopy, fourier-transform infrared reflection, and X-ray diffraction. Results revealed that the intercalation effect between nanoclay and asphalt, combined with chemical reactions between isocyanates and functional groups of nanoclay/asphalt components, effectively impeded the escape of fume molecules. Modified asphalt with 3% ATT+3% IPDI achieved an impressive fume emission reduction rate of 44.67% and enhanced basic performance of base asphalt. The findings contribute to the development of cleaner production methods for hot mix asphalt, thus paving the way for sustainable and safer construction practices in the future.