Experimental investigation into the thermal augmentation of pigmented asphalt

Asphalt binder is a temperature dependent material and is more susceptible to damage at higher temperatures. During summers, low thermal conduction and high specific heat of conventional asphalt results in extreme pavement surface temperatures and increased vulnerability. The situation demands for use of additives/modifiers that could help reduce pavement surface temperature. Thermal conduction of pigment modified/non-black asphalt mixtures is investigated in this research. Study focuses both on heating and cooling phase w.r.t time. Asphalt mixtures were evaluated for thermal conduction using larger heat sink with internal dimensions of 100×100×50 mm3. However, bituminous mixtures were examined in smaller heat sink with internal dimensions of 60×60×25 mm3. Both heat sinks were subjected to 800, 1000, and 1200 W/m2 heat flux and measurements were recorded accordingly. DC power supply was used as a heating source and silicon heater as a heating surface. Sinks were connected with data logger via calibrated K-type thermocouples. Iron oxide red and Titanium dioxide white pigments are used to decolour the black mixes. 4% by weight of total mix of each pigment is used to colour the black binder. Results have shown that at the end of 3 h of heating phase, pigment modified samples remain 8–10 °C cooler in case of bitumen binder and 4–5 °C cooler in case of asphalt mixtures. At the end of 2 h of cooling phase, a difference of 3–4 °C was noted between pigmented and conventional asphalt. Results also show that pigmented mixtures not only conduct more heat but also cool faster. Quantitatively, pigmented mixtures conduct 10%–15% more heat in comparison to the unmodified/black asphalt mixtures. The reduction in temperature susceptibility of pigmented mixtures may also help improve their high temperature performance.