Wykeham Farrance International (WFi) of the UK has launched a new catalogue of high-specification industry products for the asphalt materials-testing market.

The product range - all of which are said to meet international quality standards - include viscometers, penetrometers, ductilometers, rheometers, compactors and the new non-nuclear Pavement Density Meter (PDM).

Wykeham Farrance, renowned for its high quality materials-testing products for the soils-testing market, has for many years catered for the asphalt market in a small way. This latest initiative marks a determination to bring the same quality and scope to products for the pavement construction industry.

Wykeham Farrance also provides an advisory service to distributors and end-users in test methods, laboratory set-up and equipment maintenance.

''WFi has introduced an integrated range of products which will help civil engineers to predict the effective service life of a material,'' Joe Charlesworth, managing director, says. ''Called the Durable Pavement Design (DPD) system, it allows evaluation of a paving material's resistance to plastic deformation and cracking - the two main causes of premature failure in asphalt pavements and runways.

''By measuring these parameters in bitumen and asphalt mixes, it is possible to evaluate which materials will provide a durable asphalt pavement. The objective of the DPD system is to reduce road-building costs and optimise the use of natural resources.

As the DPD philosophy is based on end-product testing - as recommended by the Strategic Highways Research Programme (SHRP) - the engineer can experiment with traditional, recycled and other materials to produce asphalt which meets lifetime service requirements.

He continues: ''As road-builders are aware, bitumen - when used as a cement to hold together aggregates - gives the resultant mix its visco-elastic characteristics, which make asphalt such a suitable material for pavement construction. By determining a bitumen's physical properties, it is possible to identify how it will perform under particular loading and climatic conditions.

''The chart (Figure 1) shows how both modified and conventional bitumens can be classified, using the latest laboratory techniques and SHRP testing methodology.

''In asphalt design, by evaluating resistance to deformation, shearing and creep, it is possible to determine how an asphalt matrix will perform under various loading and climatic conditions (Figure 2). Such information is vital to determining the potential life of an asphalt pavement. Latest testing techniques make it possible to replicate long-term traffic conditions.

''By following the 'end-product specification' philosophy promoted by the SHRP, alternative and recycled materials can be tested for suitability in the design stage. The philosophy has advantages for both client and contractor, as it should ensure that pavement design life is achieved and that the most economical mix is supplied to meet the design criteria.''

Commenting on the new Pavement Density Meter, Charlesworth says: ''What makes it interesting is that, not only does it not depend on a nuclear source, but it allows for density measurement while the asphalt is still 'hot.

''The PDM eliminates the need for special certification or licences for operator use. It is lightweight and gives immediate readings at up to 500 per hour.''

The PDM gives instant density measurements in asphalt layers. This is extremely useful to civil engineering companies which need to monitor asphalt compaction levels achieved on highways, he points out.

''The PDM compares readings to the maximum design density, which is programmed into the unit before readings are taken. Readings are instant and this allows rapid testing of large areas. Readings can also be given continuously which is very useful when investigating potentially troublesome areas such as joints and pavement edges,'' Charlesworth adds.

The meter was tested in the US on State Route 33, a $4 million project being handled by Eastern Industries Construction (EIC), where it proved fast and accurate.

Highlighting the simplicity of ownership of the PDM, EIC vie-president Rich Frank says: "Because the PDM technology is non-nuclear, we don't have to worry about special certification for our technicians. All of the regulatory costs and concerns just go away.''

Comparisons were drawn with conventional nuclear-based meters where it is said to be proving consistently more accurate by 4 to 5 percentage points.

''The cost implications for contractors and their clients are significant. The ability to test pavement density the instant it is laid means that suspect newly-laid areas can be rolled again before the asphalt has set,'' he explains. ''The potential cost savings here are enormous, as it will dramatically reduce instances of lifting and relaying, and increase pavement life.''

In providing a full range of equipment, backed by an advisory service, Wykeham Farrance is now offering a total solution to laboratories and construction companies wishing to establish a comprehensive asphalt test capability, he adds.