Utilising natural pigments as a filler replacement on the mix design, performance and colorimetric characteristics of the microsurfacing mixture: laboratory evaluation

Coloured pavements enhance road safety and urban aesthetics. This study examined the use of bitumen emulsion and natural pigments as replacements for natural filler in coloured microsurfacing mixtures (CMMs). Coloured powders and natural fillers were analyzed, and seven colour combinations of red, yellow, and blue pigments with titanium dioxide (TiO2) were used to create CMMs. Performance was evaluated according to ASTM D6372, while colour evaluation was assessed using a colorimetric system and a spectrophotometer device. The results revealed that the mixture containing the red pigment exhibited the most appropriate performance, which was based on its particle size and properties among the CMMs. Compared to the control sample, the red combination showed improved cohesion (9.3-9.5% increase), reduced moisture sensitivity (40.1% decrease), and less vertical displacement under traffic (14.5% reduction). TiO2 was beneficial for blue and red compounds at 1-3% content, while 1% TiO2 yielded optimal results for yellow compounds.