developing in-situ permeability and air voids requirements for open-graded friction course pavement: case study

Open-graded friction course (ogfc) is a functional mixture used in high-intensity rainfall areas where there exists a risk of flash flooding. to ensure its functionality, there is a need to specify the minimum volumetric requirements on the ogfc mixture. this study aimed at developing in-situ permeability and interconnected air voids content requirements for an ogfc pavement under various rainfall intensities. seven air voids contents (16%, 17%, 18%, 19%, 20%, 21%, and 22%) of ogfc slab specimens were prepared in the laboratory, and volumetric properties (interconnected air voids and total air voids content) and hydraulic conductivities (permeability coefficient) were characterized. a rainfall simulator was developed to quantify the ultimate drainage capacities of ogfc mixtures under simulated rainfall events. it was found that the ogfc mixture with a higher designed air voids content exhibited a higher permeability coefficient and ultimate drainage capacity. however, the in-situ drainage capacity of an ogfc pavement was affected by the number and width of lanes. based on a field project that was two-way eight-lane, 2% cross slope, 20% air voids content, and 5-cm thick ogfc, the minimum in-situ permeability coefficient was determined as 825 ml/15 s. it was recommended to integrate design factors such as number and width lanes, and local rainfall intensity into the ogfc pavement design process to achieve desirable in-situ drainage functionality. © 2021, iran university of science and technology.