Cement Bound Granular Mixture

A11 Fiveways to Thetford, CBGM in a new road base layer

A11 Fiveways to Thetford



Highways Agency


Tarmac Contracting

Location type

A11 Fiveways to Thetford


May 2014

The challenge

Tarmac Pavement Solutions were appointed as key supplier to this £100m Highways Agency project to upgrade the last remaining single carriageway section of the strategic A11 route to Norwich, between Fiveways and Thetford. The client was keen to encourage more sustainable solutions that would minimise the impact on the environment and on local communities during construction. During the construction there was a substantial amount of tar contaminated arisings to deal with and the challenge was to re-encorporate this back into the contract eliminating the need for it to be sent to landfill.

Our solution

After discussions with the main contractor and investigation of the site, Tarmac Pavement Solutions were asked to supply and install approximately 150,000m2 of CBGM, in a single 175mm layer to form the base of the new road and circa 4,000 tonnes of CRBM in side roads. The CBGM was designed and manufactured incorporating 25% of the tar arisings and the CRBM, 88% of the tar arisings. They were then laid using a modified, GPS controlled paving machine to form a highly consistent base layer. At all times Tarmac Pavement Solutions worked within strict limits on noise and airborne dust set by the client and main contractor. Over 84 thousand tonnes of CBGM were processed and laid on site starting in May 2013.

Results and benefits

Using site-processed CBGM supplied by Tarmac Pavement Solutions, provided a number of benefits for the client. It reduced inbound and outbound haulage and disposal for this contaminated material excavated from site. As a result it saved significant time and cost for the client and reduced disruption from site traffic for local road users. Replacing a portion of the aggregate with site won granular material also helped to reduce the carbon footprint of the contract. In addition to the CBGM and CRBM, Tarmac also supplied and installed several Roller Compacted Concrete trials on the main carriageway.

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