OGFC

Two of the more recent innovations for using sulfur modified binders are in conjunction with recycling old asphalt pavements and the construction of open graded friction courses (OGFC). 

SEA-OGFC mixes over conventional mixtures is reflected in their higher coefficients of permeability, Ky, and flooding rainfall intensity, If shown in Table 3 [50]. 

The influence of highway pavement surface type on tire/pavement noise was studied (Bennert et al., 2006). It was found that the open-graded friction course (OGFC) with the hot mix GRT-modified asphalts attained the lowest noise levels. Also, the GRT-modified OGFC mixes exhibited finer aggregate gradations than the traditionally used OGFC. 

OGFCs may also be placed to reduce the tyre-pavement interface noise and may also be placed to reduce the occurrence and severity of reflective cracking. 

According to ASTM D 6932 (2008), the binder content of an OGFC mixture typically ranges from 5% to 7% when paving grade bitumen is used, from 6% to 8% when modified bitumen is used or from 8% to 10.5% when bitumen-rubber is used. 

The binder should be selected on the basis of ambient temperature, traffic and the expected functional performance of the OGFC mixture. The selected bituminous (asphalt) binder should satisfy the requirements of ASTM D 6373 (2007) (performance-graded asphalt binder). However, other grades of asphalt binders, such as penetration grade (ASTM D 946 2009) or viscosity grade (ASTM D 3381 2012), may be suitable. 

Source Reprinted from ASTM D 7064, Standard practice for open-graded friction courses (OGFC) mix design. West Conshohocken, Pennsylvania. US ASTM International, 2008. With permission ( ASTM International). 

The mix design of the OGFC mixture, in accordance to ASTM D 7064 (2008), after selecting the constituent materials consists of the following stages ... 

For a better performance of the OGFC mixture, there should be stone-on-stone contact in the coarse aggregate skeleton (all coarse aggregate is retained on the 4.75 mm sieve). 

The condition for stone-on-stone contact within an OGFC mixture is defined as the point at which the per cent of voids of the compacted mixture is less than the voids in the coarse aggregate (VGA) in the dry-rodded test. The dry-rodded test is carried out in accordance to ASTM C 29/C 29M (2009) from which the VCAo, ( is determined using the following equation ... 

The OGFC mixture meeting all the above requirements is the one that determines the optimum binder content. 

The production and placement of OGFC, as well as sampling and testing during construction, and the construction procedure are carried out in accordance to ASTM D 6932 (2008). 

As it was mentioned, PA or OGFC is used in surfacing airport pavements. FAA standards call this type of mixture porous friction course (PFC) mixture. 

For the surface layer, in particular, the asphalts most commonly used nowadays are (a) asphalt concrete for very thin layers (AC-VTL), (b) porous asphalt (PA), (c) open-graded friction course mixture (OGFC), (d) stone mastic asphalt (SMA), (e) single or double surface dressing (S-SD or D-SD) and (f) micro-surfacing (MS). Table 10.17 gives the comparative properties/characteristics for all the abovementioned surfacing materials. 

OgFC H], Benzoic acid, 3-fluoro-, rhodium complex, 27 292... 

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