Fracture resistance of asphalt mixtures under mixed-mode I/II loading at low-temperature: Without and with nano SiO2

Abstract

Increasing traffic congestion especially in cold climates has increased the damage caused by low-temperature cracks (LTCs) in the asphalt mix where the constituents are not able to withstand the loads required in these climates lonely and using the modifier is undeniable. In recent years, some research fields have been conducted on the use of nanomaterials as a modifier in asphalt mixtures to improve their properties. In accordance with previous researches, one of the nanomaterials that have appropriate effects on the performance of asphalt mixtures is Nano-SiO2. In this study, the effect of Nano-SiO2 on the incident of low-temperature cracks in asphalt mixtures is experimentally investigated. For this purpose, the semicircular bending test (SCB) under mixed-mode I/II loading is used for investigating the effect of Nano-SiO2 on forming cracks in asphalt (i.e., vertical and angular crack) at different temperatures of −5℃, −15℃, and −25℃. Results show that the maximum stress intensity factor (SIF) of the modified asphalt mixtures is related to specimens which have angular crack under pure opening mode, while the maximum critical SIF is improved when Nano-SiO2 is added to specimens which have vertical cracks under mixed-mode I/II with Me = 0.6 at −25℃. Furthermore, the critical SIF of all specimens having both vertical and angular cracks is significantly improved by adding 1.2% of Nano-SiO2 at all temperatures.