Preparation and Properties of Cold-Mixed Epoxy-Asphalt Mixture Based on Fractal Theory

Cold-mixed epoxy-asphalt mixture (CMEAM) has gradually received increased attention in steel bridge pavement construction due to its excellent road performance and low harmful gas emissions. According to previous studies, EA-05 and EA-10 (epoxy asphalt mixture with nominal maximum particle sizes of 4.75 and 9.5 mm, respectively), are advised to be applied in CMEAM and hot mixed epoxy asphalt mixture (HMEAM), respectively. This only considers the temperature factor and ignores the gradation influence. To make a clear gradation design illustration for CMEAM, fractal theory was introduced to quantitatively distinguish the differences among various gradations from EA-05 and EA-10 using fractal dimension as an index. In addition, to offer more design parameters for CMEMA, the passing percentage on key sieves whose passing percentages have high correlation coefficients with road performance, mixture structure parameters including stone-on-stone contact (SSC) and stability of coarse aggregates (S) are also considered as indexes. According to the requirements in the foregoing specifications, the Marshall stability test, low-temperature indirect tensile strength test (ITS), and freeze-thaw splitting test were carried out on CMEAM. Test results showed that Marshall modulus (MM), tensile strain (εT), and tensile strength ratio (TSR) have a good quadratic relation function with fractal dimensions. When the fractal dimension ranges from 2.4522 to 2.4782, the low-temperature performance and moisture stability of EA-05 are better than those of EA-10, and Marshall stability also meets technical requirements. Meanwhile, the key sieves of EA-05 are confirmed as 0.075 mm, 0.15 mm, and 2.36 mm, and those of EA-10 are 0.075 mm, 1.18 mm, 2.36 mm, and 4.75 mm. Finally, the optimum ranges of SSC for EA-05 and EA-10 are 110.4%–110.6% and 67.5%–72.7%, respectively; and of S are 118.5%–118.7% and 70.2%–73.4%, respectively.