Analysing the effects of the mesoscopic characteristics of mineral powder fillers on the cohesive strength of asphalt mortars at low temperatures

• The mineral powder fillers have influence on cohesive strength of asphalt mortars.
• Mesoscopic void have direct correlation with cohesive strength of asphalt mortars.
• Mesoscopic void can be tested by using infiltrating free-pressure water.

The mesoscopic characteristics of mineral powder fillers were tested, and their effects on the cohesive strength of asphalt mortars at low temperatures were analysed. The BT-1600 image particle analysis system was employed to test the mesoscopic grading, length-to-diameter ratio and circular degree of mineral powder fillers. Infiltrating free-pressure water was used to test mesoscopic void characteristics. Three kinds of asphalt mortars were prepared with different mineral powder fillers. Their low-temperature cohesive strengths were tested quantitatively according to a technology for testing tensile cohesive strength. Results showed that the differences in the mesoscopic characteristics of the three kinds of mineral powder fillers led to different low-temperature cohesive strengths of the three asphalt mortars, although their preliminary screening results were nearly the same. The mesoscopic void characteristics of mineral powder fillers can result from the combined effects of mesoscopic grading, length-to-diameter ratio, specific surface area and circular degree, among others. And it can also estimate the proportions of fixed and free asphalts. By using the mesoscopic void characteristics of mineral powder fillers as intermediaries based on the proportions of fixed and free asphalts, we can identify the effects of these characteristics on the low-temperature cohesive strength of asphalt mortars.