Retread and Regen: recycling a road in place

A plain English summary of REA Technical Data Sheet No.10, revised by the Association’s Technical Committee in August 2025. The datasheet is the authority; this page exists so the guidance can be read, searched and quoted without opening a PDF.

The problem these processes solve

Plenty of coated macadam, grouted and surface dressed roads have sound foundations but a cracked, crazed and deformed surface. The conventional answers are to overlay with new macadam or to replace the surfacing. Both are costly, and an overlay brings the further expense of raising footway and kerb levels.

Retread and Regen take the other route. The existing aggregate has normally suffered negligible deterioration, so it can be recoated to reshape the road and restore a skid resistant surface. Both are established forms of recycling road pavements, and unlike many newer ideas they need no heat. They work on water bound, dry bound, bitumen bound and tar bound surfaces alike.

One caution. The processing may uncover tar bound material, which has to be dealt with appropriately and with the health and safety implications in mind.

How the process runs

In outline: scarify the old road to a suitable depth, break the scarified material down to the required size, reshape it, mix it with a selected class of emulsion by spraying, then harrow and roll. Additives such as Portland cement to BS EN 197-1 can be introduced to improve stiffness and curing times. The road is then normally surface dressed. BS 9228 gives the specific guidance for both processes.

1. Break up. The existing surface is broken to a depth of up to 150mm, then harrowed and rolled until it is reduced to a suitable grading. The surface is reshaped to the required profile with an approved grader.
2. Emulsion. Depending on the grading and the type of surface, bitumen emulsion to BS EN 13808 is applied by bulk distributor. After every application except the last, harrows are traversed to turn the stone and spread the emulsion evenly.
3. Reshape and roll. If necessary the road is regraded, then rolled, preferably with an 8 to 10 tonne deadweight roller. Surface voids are filled with 6/14mm chippings at an appropriate rate and rolled.
4. Seal. Bitumen emulsion to BS EN 13808 class C60B3 or C69B3, or a similar polymer modified grade, at 0.9 to 1.2 litres per square metre, blinded according to the texture with 2/6mm or 4/10mm chippings, then rolled.
5. Surface dress. After a period that may run from a few days to three months depending on the weather and the traffic, the treated surface is dressed with class C60B3 or C69B3 or a similar polymer modified emulsion, using 2/6mm or 4/10mm chippings. Depending on the road category, the rate of emulsion should be increased by about 0.2 litres per square metre over the recommendation for hard surfaces in TRL Road Note 39. A slurry surfacing or a bituminous wearing course may be applied instead.

UKCA and CE marking

Construction products covered by a harmonised European standard have had to be CE marked to be placed on the European market since the Construction Products Regulation was fully implemented in June 2013. The UK introduced the UKCA mark in January 2021, and the transition period has been extended indefinitely, so both marks can continue to be used.

Download Technical Data Sheet No.10 (PDF)Retread and Regen. Revised August 2025.

References

BS 9228:2021, Recycling of roads and other paved areas using bitumen emulsion, foamed bitumen or hydraulic material. BS EN 197-1, cement. BS EN 13808, cationic bituminous emulsions. TRL Road Note 39, Design Guide for Road Surface Dressing.