Evaluation of the field-aged performance of foamed warm mix asphalt: Comparisons with hot mix asphalt

The foamed warm mix asphalt (FWMA) has been widely used as a sustainable construction technique in pavement engineering, yet has not yet been fully studied for its aging performance or durability. Here we aim to examine and evaluate the performance variation characteristic of FWMA compared with conventional hot mix asphalt (HMA) under long-term service conditions. The performance evolution of FWMA core samples drilled from four highways was compared to that of ordinary HMA, which was simultaneously constructed. Fourier transform infrared (FTIR), dynamic shear rheology (DSR), and bending beam rheometer (BBR) tests were respectively performed to evaluate the aging degree, high-temperature, and low-temperature rheological characteristics. The results demonstrated that the aging resistance of foamed WMA was slightly diminished under construction conditions with no temperature reduction. With increased service time, the rheological characteristics of FWMA were enhanced at high temperatures, while dete-riorated at low temperatures. The foaming water and service time were primary determinants of the aging as well as high and low-temperature rheological properties of FWMA without tem-perature construction reduction. Additionally, the aging degree of FWMA under short-term and long-term service was smaller than HMA when the construction temperature decreased. The rheological characteristics of FWMA were inferior to those of HMA during both short-term and long-term service stages. Under conditions of temperature reduction, foaming water and mixing temperature exhibited a considerable influence on the aging and rheological properties of FWMA at high and low temperatures. Therefore, the amount of water used for foaming and the tem-perature of production should be strictly control in the foamed warm mix asphalt technology.