Concrete @ your Fingertips

Remedial repair of cracks in floors

Cracks that are considered to be non-structural but may affect the serviceability of a floor may need remediation. The remedial works to cracks should be regarded as being required for serviceability purposes only and not as full ‘structural’ repairs.

Once crack edge damage occurs and a linear zone of damage produces ‘islands’ or loss of concrete it becomes extremely difficult to determine the actual underlying crack width. The decision to undertake remedial works should be based upon the extent of the crack edge damage, not solely on the original crack width. However, it would be prudent to fill cracks over about 1mm wide (assessed on unspalled area) when they are trafficked by small hard wheels.

Ideally cracks should just be filled to protect the edges from damage. Routing out along the joint line is preferably avoided, except where the crack edge damage or ‘fretting’ has already produced a notch or groove or a narrow zone of badly fragmented surface mortar. Some of the cracks may be ‘live’, in that movement across them might continue due to variations in slab loading, temperature and moisture content. There is a risk that fine cracks could occur at previously filled cracks. The cracks could be filled with proprietary low viscosity crack filling materials, the installation of the materials being in accordance with the suppliers’ instructions. Different materials and methods may be required for different crack widths and/or degrees of edge damage. Filling of cracks should only be undertaken where necessary to protect crack edges, as filling and repairing cracks tends to make them more visually apparent. The cracks that require filling should be determined by an inspection of the floor.

Acknowledgement: The Concrete Society

Concrete Bookshop - Members receive 40% discount on Concrete Society publications

Concrete industrial ground floors – user expectations

Crack width measurement

Maintenance and repair of industrial concrete floors - GCG10