Tarmac Toproc Ready-Mix Concrete- Brockworth Bypass, Gloucestershire

Toproc SS has proved to be most successful on a whole range of fast track construction projects, one being in this bridge stitching example for Wimpey Construction.

The Brockworth Bypass involved the construction of a new interchange on the M5 and new bridge deck alongside the existing one. The old and new decks were then ‘stitched together’ with concrete, the motorway being completely closed during the pour and not opened until the concrete in-situ achieved a strength of 10 MPa. This strength was required to ensure that the vibration generated by the moving traffic did not affect the bond between the rebar and the concrete.


On this type of bridge stitching, it is very difficult to get any concrete to develop its strength quickly as any heat generated by the mix is rapidly conducted away by the rebar which passes through the stitch into the adjacent concrete and by the heat sink effect of the adjacent concrete. Also the very nature of these pours requires them to be carried out at night when the ambient temperature is very low, in this case 5-9°C. Nevertheless, the Toproc SS delivered to this site developed by 20MPa in 6 hours, which enabled the motorway to be opened only 6 hours after pouring the concrete.

The success of such a complex pour is dependent upon a whole range of factors, not just the performance of the concrete. Effective liaison between engineer, contractor and Topmix, logistic planning, trial pours and choice of placing and curing methods all combine to ensure that the job is a success.

Product Used: Toproc SS ready-mix concrete

Beneficial Features: Ultra rapid strength development, confidence, easy placement

Compressive Strength: 20 MPa in 6 hours, 92 MPa in 28 days

This information has been sourced, reviewed and adapted from materials provided by Tarmac Ltd.

For more information on this source, please visit Tarmac Ltd.


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