Experimental Investigation on the Clogging and De-clogging Behaviour of Open Graded Friction Course Mixes

Open graded friction course (OGFC) mixes have highly permeable structure, facilitating effective drainage. However, the performance and durability of these surfaces can be adversely affected when the voids get clogged. This paper presents the findings of an experimental study focused on the clogging behaviour of OGFC mixes when subjected to three different clogging materials (CM) intended to block the pores of the mix. Falling head permeability tests were conducted on OGFC samples prepared with Natural Rubber Modified Bitumen (NRMB 70) and cellulose fiber. The study evaluated the performance of these mixes in terms of stone-on-stone contact condition, air voids and permeability. To determine the clogged and de-clogged permeability of the mix, clogging materials collected from various road surfaces, including the median of a newly developed National Highway (NH-66) section, a tared parking lot, and the roadside, were used. These clogging materials were classified based on their index properties. To retrieve the permeability of clogged specimens, a de-clogging technique involving sweeping and vacuum suction (SV) was adopted. The effect of these clogging materials on the percentage recoverable permeability loss is also investigated. The study also investigated the combined effects of used engine oil and dirt on the permeability of the OGFC mix to bring out the clogging caused by the absorption of engine oil into the pavement surface over a period of time. The study emphasized the need to investigate the nature and properties of soil surrounding open graded surfaces to prevent excessive clogging of voids. Furthermore, the study also highlights the importance of managing clogging in OGFC mixes and offers valuable insights into the impact of different clogging materials on the mix's permeability and regained permeability and emphasize that the particles finer than 75 microns are the major clogging material which should be avoided near OGFC pavements to minimize the clogging.