High Friction Roads | Education

High Friction Surfacing (HFS), commonly referred to as anti-skid surfaces, involves specialized pavement treatments that integrate durable, polish-resistant aggregates bonded to roads using a resin. While both hot and cold application methods exist globally, the U.S. predominantly utilizes cold applied high friction systems.

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Importance of Aggregate Characteristics

The selection of aggregates is crucial for ensuring the skid-resistance of the HFS system. The surface texture of the aggregate is vital as it directly influences skid resistance. Key aggregate characteristics for HFS include polish resistance and abrasion resistance, typically evaluated through polished stone value (PSV) and aggregate abrasion value (AAV) or Los Angeles (LA) Abrasion Value. The PSV measures an aggregate's ability to resist polishing due to traffic, with higher values indicating better retention of microtexture. Conversely, abrasion resistance reflects an aggregate’s resilience against wear under traffic loads. Generally, aggregates selected for HFS are sized at 3-4 mm, following specifications that mandate at least 95 percent to pass through a No. 6 sieve and a maximum of 5 percent through a No. 16 sieve.

Traditionally, calcined bauxite is the primary aggregate material utilized for HFS. Alternatives such as flint, granite, and steel slag have also been applied.

Binder Characteristics

Various resin binders are employed in HFS systems, including epoxy, rosin-ester, polyurethane, polyester, and methyl methacrylate. Below is a brief overview of common binders:

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Epoxy-resin: This two-component binder system consists of a resin mixed with oil to enhance fluidity, and a curing agent combined with bitumen, oil, and accelerators, prepared on-site.
Rosin-ester: This binder comes premixed, where the resin and aggregates are packaged as dry powder. At the work site, this powder is heated and spread.

Polyurethane-resin: This binder comprises two liquid components and one powder and cures through a chemical process, typically applied by hand, with aggregates added afterward. These binders facilitate faster curing in cold weather conditions.

Acrylic-resin: Similar to epoxy-resin but offers a quicker curing time.

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