Highways Agency specification

The soundness test adopted in BS 812 [8.4] uses magnesium sulfate. The Highways Agency Specification [8.7] gives soundness limits for coarse and fine aggregate of 65 and 75 % respectively. 

Highways Agency, Specification for Highway Works, HMSO, London, 1991. 

The UK Highways Agency s specification [8.7] refers to unbound material for subbase and road-base (Table 8.4). A CEN specification is in preparation (see section 8.8.1). Specifications for use in tropical and sub-tropical countries are described in [8.16]. 

The Highways Agency s Specification 1991 [8.7] identifies strength, durability and cleanliness as being important factors, but places the responsibility on the specifying engineer to assess the requirements for a particular application. A CEN Standard is in preparation (section 8.8.1). 

Dense limestones weather well and easily meet the requirement in the Highways Agency s Specification [8.7] of a magnesium sulfate soundness value [8.4] greater than 75 %. 

Concrete Overlays (used on North American highway bridges according to specifications developed by highway agencies). 

Highways Agency. 2009a. The Manual of Contract Documents for Highway Works (MCHW), Volume 1 Specification for Highway Works, Series 600 Earthworks. London Department for Transport, Highways Agency. 

When reclaimed materials are to used in the Type I mixture, such as asphalt (Class R ) or other materials (Class X), the maximum permitted content recommended by the British specifications is less than 10% and 1%, respectively (% by mass) (Highways Agency 2009b). 

The maximum permissible thickness of a compacted single layer, according to British specifications (Highways Agency 2009b), is 225 mm. If the thickness of the base/sub-base is more than 225 mm, compaction should be conducted in more than one layer. In the same specification, the minimum thickness of compacted layer is required to be 110 mm. 

According to British specifications (Highways Agency 2009b), the compaction requirements for sufficient compaction of base/sub-base unbound mixtures using various types of compaction equipment (plant), when the compacted layer thickness is 110, 150 or 225 mm, are given in Table 10.8. 

Table 10.10 provides the minimum percentages required when cement is used as a hydraulic binder, together with the minimum values for all binders or binder constituents used today, as specified by British specifications (Highways Agency 2006). 

Table 10.11 gives the aggregate property requirements of all the HBMs proposed by British specifications (Highways Agency 2009b). 

Highway agencies are encouraged to perform a periodic assessment of the potential for systemwide, route, or route section safety upgrading design in connection with or in addition to programs to identify and correct specific hazardous locations. 

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