Asphalt and asphalt products

These materials have traditionally been used for surfacing motorways and trunk roads. During the laying process pre-coated chippings are added with a Polished Stone Value (PSV) suitable for the traffic condition on the site concerned. Previous requirements included stiffness values such as 2 – 8Kn, 4 – 8kn etc, however these have largely been superseded by the new European Standards and PD 6691 which simply require Design Hot Rolled Asphalt. The performances of such materials are designed by the manufacturer through a programme of type testing and factory production control. However, the customer must always specify whether Type F (sand fines) or Type C (crushed rock fines) are required.

These materials can be used for the surfacing of a wide variety of sites, Trunk Roads, Minor roads, Estates roads, Heavy vehicle parking areas, Stress sites etc. The material does not require the addition of pre-coated chippings, therefore the (PSV) Polished Stone Value of the coarse aggregate within the mix should reflect the values required on each site. This group of material is produced using either sand fines (Type F) or crushed rock (Type C), they are all design mixtures, although mix stability is not normally specified. The normal grade of bitumen 100/150, however other grades are available.

These groups of materials are used as a base/binder course combination and may be laid up to 150mm thick. Available sizes are 10mm, 14mm and 20mm and often replace as a single layer a traditional base and binder course construction. These are very dense materials with a thick binder film which offers high durability and stability within the lower surface layers of road construction. Their use is normally restricted to motorways and other trunk roads and requires an experienced contractor to achieve the required high in situ densities. All such mixes are designed by the manufacturer and should not be considered for use in small works

These materials are dual purpose and can be used either as a Dense Base (Roadbase) or Binder Course layer. Such materials are generally employed as support layers on highly trafficked sites such as motorways and trunk roads due to their ability to withstand greater traffic loading. They are specified in the Specification for Highway Works Cl 929 and PD 6691, and are always design mixtures. Unlike recipe mixtures, these are designed in accordance with European Standards and have to comply to a number of fundamental tests such as wheel tracking, voids etc. They are not intermixed within a single pavement structure, and are considered inappropriate for use on other sites. A design is undertaken for each aggregate type.

Hot Rolled Asphalt Base (Roadbase) materials are the first layer over the sub grade or sub strata and the primary layer to provide the strength of the overall surfaced road. Depending on the design characteristics of the road they may be laid in one or more layers. This group of materials is produced in sand fines (Type F) and crushed rock fines (Type C).

Binder Course materials act as a support layer prior to the finished Surface Course and are applied over the Asphalt Base (Roadbase) layer - a sort of filling within an Asphalt Base (Roadbase)/Surface Course sandwich. Asphalt and dense macadam materials are usually never intermixed in the road structure. Regulating Course materials are used to "make up" surfaces and even out any unwanted undulations within road surfacing layers. This group of materials are produced in sand fines (type F) and crushed rock fines (Type C).

Both Design Dense Base (Roadbase) and Binder Course materials are specified in the Specification for Highway Works Cl 929 and PD 6691 of the contract documents. As with other design materials, they have to comply to a number of fundamental minimum values to ensure durability. Such materials are generally employed as support layers on highly trafficked sites such as motorways and trunk roads. Heavy duty and Dense Macadams are not generally intermixed within a single pavement structure. Unless otherwise required in Appendix 7/1 of the Contract Documents, Design materials are required by default.

The following materials are Dense Base (Roadbase) layers i.e. they are the first layer over the sub grade or sub strata and the primary layer to provide the strength of the overall surfaced road. Depending on the design characteristics of the road, Dense Base (Roadbase) materials may be laid in one or more layers. Heavy Duty Dense Base (Roadbase) is often laid where high traffic densities are likely, such as motorways and major trunk roads and offers greater durability and resistance to cracking than traditional Macadam, Heavy duty and Dense Macadams are not generally intermixed within a single pavement structure. Recipe mixtures are no longer standardised (ie one grading and binder content fits all) and each asphalt manufacturer will offer their own recipe mixtures based on previous performance. General guidelines for the composition of recipe mixtures are given by BS EN 13108-1 and the UK guidance document PD 6691

Binder Course materials act as a support layer prior to the finished Surface Course and are applied over the Dense Base (Roadbase) layer - a sort of filling within a Dense Base (Roadbase)/Surface Course sandwich. Occasionally, construction is halted at the Binder Course layer prior to receiving the surfacing surface, or the latter is delayed for economic reasons. In these circumstances, the Binder Course layer is required to act (albeit temporarily) as the running surface and a minimum Polished Stone Value of the aggregate may be required to enhance the skid resistance of this layer. We are also occasionally asked for Binder Course materials to be "enriched" to suit customer requirements. This means that the Binder Course has an increased binder content over and above that required PD 6691. We would always recommend using an enriched binder course when being used as a temporary running surface.

All of the following materials employ binder modified by varying degrees of flux oil to delay the setting properties of the bitumen. Flux oil is similar to household creosote (a wood preservative often applied to fencing) and is a by-product of the petroleum industry. Flux oils are added during mixing (i.e. at the asphalt plant) and the setting properties of the bitumen are delayed in an approximate proportion to the volume of flux oil added. Delayed set materials are particularly useful to Local Authorities who only require small tonnages for reinstatement works. Such stored materials need to be well sheeted to prevent premature setting resulting from inclement weather conditions. They should always be viewed as a second best alternative to materials produced in penetration grade bitumen. The oil added to the mix may take some time to fully evaporate, which in turn may result in a reduction in early life performance of these materials and potential softening in warm weather. We only recommend such materials for use in temporary works.

Macadam Surface Courses are offered in a size range from 4mm Fine Graded to 14mm Open or Close graded. As the term implies, these materials are used as the final running surface of a construction. Typical applications include the final finish to minor roads, estate roads, factory or other large car parks and indeed private house driveways. However, care should be taken when selecting the paving grade binder to be used with such materials and we recommend a minimum of 100/150 paving grade bitumen for the above and preferably (where possible) the use of 40/60 paving grade bitumen. Although we offer the softer 160/220 paving grade bitumen we only recommend its use for temporary works only given its low durability particularly in warmer weather.

MaxiDrive and MaxiDrive+ have been designed by MQP to satisfy the increasing demands being placed on domestic driveways by climate changes and power steering.  These products utilise innovative combinations of material plus a modifier and have been designed to withstand stresses caused by increases in temperatures and the action of power steering. Please refer to our technical department for further information on these products.

MQP era® 140 incorporates a specialist bitumen that allows asphalt to be produced at a reduced temperature (up to 30 degrees lower), when compared to conventional hot mix asphalt. This in turn leads to a fall in the level of embodied CO₂.

All of these materials are used for the same applications as those without pigment. Coloured materials are used for either aesthetic appeal or to emphasise a particular road hazard (e.g. a sudden reduction in speed limit on the approach to a built up area or to junctions with a history of accidents). They are generally produced using pigmented conventional penetration grade bitumen with the local coarse aggregate.

These materials have traditionally been used for surfacing trunk roads, minor roads, estate roads, car/lorry parks. When laid on the highway during the laying process pre-coated chippings are added with a (PSV) Polished Stone Value suitable for the traffic condition on the site concerned. On off highway sites pre-coated chipping may or may not be used depending on the conditions prevailing on each individual site. Asphalt with lower stone contents is normally employed as regulating courses or temporary surfacings.

These materials are used in a variety of surfacing applications from footpaths to major car and lorry parking areas. They are produced to satisfy the industry demand for a range of Asphalt surfacing material with either different sized aggregate or stone contents to those specified within European Standards. In addition, some of the mixes are used as regulating materials.

Similar in many ways to the design mixtures, these materials generally reflect the industry need to use products with sizes or stone contents not specified in current EN Standards. These mixtures are also produced in either sand fines (Type F) or crushed rock (Type C), with a range of bitumen grades. They are suitable for estate roads, car / lorry parks, and areas of stress. The material does not require the addition of pre-coated chippings, therefore the (PSV) Polished Stone Value of the coarse aggregate within the mix should reflect the values required on each site, although PSV is only an issue on sites where traffic is of a reasonable high speed.

These materials differ significantly from traditional Dense Macadams in as much as they are gap-graded and have low fines content. Often used as a cost effective or temporary alternative to Dense Macadams, primarily within areas of low trafficking; e.g. Footpaths. We would not recommend such materials for use within car parks or driveways given the high stresses caused by modern power steered vehicles.

Stone Mastic Asphalt (SMA) is a high strength material that produces a surface that in many instances out-performs that of traditional Hot Rolled Asphalt (and pre-coated chippings where required). These materials are particularly suited to sites of high stress, such as lorry parks, industrial areas, Motorways, Trunk Roads etc. They provide a reduction in surface noise through negative texture, and often provide benefits during the laying process, as there is less laying equipment required and can generally be trafficked earlier than conventional asphalt without the risk of premature surface failure. On many road sites the Skid Properties (PSV) of the surfacing material is important and SMA is produced with a variety of aggregates with PSV ranging from 56 to 68. In addition to using traditional binders, SMA can be manufactured using a fuel resistant binder which makes it particularly suitable for areas at risk from fuel spillage (bus stops, lorry parks etc). 6mm SMA is particularly suited to House Drives and Car Parks where it is more resistant to the scuffing action of vehicles turning in confined spaces.

Contractors wishing to register for approval to lay Durafalt should initially contact MQP technical services.