Definition

High Friction Surfacing (HFS), commonly termed Anti-skid, refers to a surface treatment approximately 3-5mm thick which provides enhanced surface skid resistance for drivers to brake under emergency conditions at hazardous locations. HFS is defined by Industry as having a minimum skid resistance value (SRV) of 65 measured using the portable Skid-Resistance Pendulum Tester as defined in TRL Report 176, Appendix E. The aggregate used is Calcined Bauxite (normally buff or grey), which is usually imported from either China or India. Typical locations for HFS installation include approaches to roundabouts, pedestrian crossings, junctions, sites with steep gradients and dangerous bends.

Why is Calcined Bauxite Used for HFS?

Calcined Bauxite is the perfect aggregate for HFS in that it has a high PSV and low AAV typically between 1 & 3. It has a typical relative density >3 and a Moh’s hardness of 9, compared to diamond being the hardest with a Moh’s value of 10. It is a very hard wearing and abrasion resistant aggregate. The aggregate should be cubical (block) shape, very clean with a 1-3mm grading as recommended by the RSTA HFS Code of Practice document.

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