A new industry Code of Practice for Grouted Macadam Surfacing has been published by the Road Surface Treatments Association (RSTA). It forwards industry best practice and has been peer reviewed and endorsed by ADEPT, the Association of Directors of Environment, Economy, Planning & Transport.
Grouted Macadam surfacing is used to re-profile and strengthen the road surface – thereby providing improved texture, skid resistance and prevention of water ingress. It offers an alternative to standard asphalt and macadam surface courses.
There are two main types of Grouted Macadam surfacing – those grouted with an asphaltic grout and those with a cementitious grout. Both provide impervious finishes with an extended service life.
Asphaltic Grouted Macadam consists of a hot, paver laid, open-graded asphalt, purposefully designed receiving course, laid to a depth of between 30mm and 50mm, which is then sealed with an asphaltic grout. It provides an impervious surface course, combatting water ingress with the flexibility to withstand underlying movement. The sealing of the surface course also prevents fretting, reduces the speed of binder oxidation and reinforces the strength and elastic stiffness of the surface course. The material is ideally suited to the resurfacing of flexible or concrete rural and residential highways.
Cementitious Grouted Macadam consists of a hot, paver laid, open-graded asphaltic, purposefully designed receiving course, typically laid to a nominal depth of between 35mm and 50mm with a controlled void content which is subsequently filled with a resin cementitious grout. This provides a hybrid between asphalt and concrete with fast installation, minimal downtime and a resulting stiffness that falls between concrete and conventional bituminous surfacing materials. It has a high heat resistance and is therefore less temperature susceptible than traditional bituminous materials. A flexible, jointless, heavy-duty surface course, it is capable of withstanding intense traffic loadings and fuel / leachate contamination to minimise rutting or deformation. This material is ideally suited to the surfacing of high-stress areas.
The new code underlines the need for careful consideration of a wide range of details, to plan and design the work carefully and to use only HAPAS (or equivalent) approved installers certificated to BS EN ISO 9001:2008 / 9001:2015 and National Highways Sector Scheme 16. As there is no British Standard design criteria for Grouted Macadams it is important for the client to satisfy himself that the contractor has sufficient knowledge and experience, that the product is suitably established and has been adequately tested and approved to perform as expected, and that it has demonstrated the durability required to meet the necessary service life.
The health and safety, environment, training and quality assurance responsibilities of client and contractor are set out by the code. It also provides guidance on site planning, programming, co-ordination and traffic management. A useful inclusion is the pre-contract, on-site and post-contract check-lists.
Copies of the Code of Practice for Grouted Macadam Surfacing may be downloaded from the RSTA website: www.rsta-uk.org/publications