Applicability of larger particle size aggregate in asphalt concrete used as impervious panel material helps reduce material costs while improving its mechanical properties. This paper presents a method that increases the maximum particle size Dmax of its concrete aggregate from 16 mm to 26.5 mm and 31.5 mm. Optimal mix parameters are obtained through mix proportion tests for three sets of asphalt concrete with different maximum particle sizes; Their splitting

uniaxial compression

tensile

and slope flow tests are conducted. The performances are compared and the influence of aggregate size on mechanical properties is examined. The results demonstrate the maximum particle size has a significant impact on both its mix proportion parameters and properties. With the maximum particle size increasing

the gradation index increases

while the specific surface area of aggregate and the asphalt-aggregate ratio both decreases (from 7.0% to 6.2%)

reducing material costs effectively. Appropriate increase in the maximum particle size helps improve splitting strength (an increase of 4.02%) and compressive strength (an increase of 14.07%) of asphalt concrete

and reduce the slope flow value. However

when the maximum particle size is too large

tensile strength decreases (a reduction of 5.78%)

brittle failure dominates the failure mode

and toughness and deformation adaptability are weakened. This study would lay a theoretical basis for further research on large particle size aggregates used in impermeable layer asphalt concrete to build pumped storage power station panels.