Cement bound sand

Cement bound sand (CBS) is a weak mix primarily used as a bedding and infill material to protect underground cable installations.

It has a low thermal resistance to conduct the heat produced during electricity transmission away from low and high voltage cables and, as it is a weak 14:1 sand to cement ratio, it is relatively easy to remove if maintenance or removal of cables is required.

Our CBS is compliant with Energy Network Association Technical Specification (ENA TS) 97-1 and National Grid Technical Specification (NGTS) 3.05.07. Certificates are available on request.

Compliant CBS is used to ensure that the thermal conductivity around the cables is of a known value and will remain consistant for the length of the cable being installed.  This allows the rating of the cable – its ability to carry the required current – to be maintained at the designed capacity.

All backfill materials used around power cables (such as CBS or unbound cable sand) must be fully compacted around the cables to ensure any trapped air is removed. If the materials are not compacted correctly, the trapped air will act as an insulator and adversly affect the carrying capacity of the cable. This could cause hot spots and result in premature failure or a reduced rating for the cable system installed. Regular tests should be carried out to ensure the correct level of compaction and thermal resistivity is achieved.


Do you offer CBS available nationally?

Yes, Heidelberg Materials offers national coverage and our CBS complies with the requirements of ENA TS 97-1 and NGTS 3.05.07, so you can be assured of its quality. Please contact our technical sales team for more information on telephone 0330 123 4535 or email marketing@uk.heidelbergmaterials.com

Will any 14:1 sand cement mix be suitable?

No, as not all materials have the required thermal conductivity. Please ensure that any material used has current UKAS acredited test results, which take approximately four weeks to carry out,  to provide assurance that the material is fit for purpose.

How quickly does CBS ‘go off’?

CBS has a low moisture content and its performance will be significantly reduced if it is allowed to dry out too quickly. We would recomend that it is placed and compacted within 2 hours, although this could be extended provided the material is covered in polythene sheeting to prevent moisture loss. 


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