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Find out more1 February 2023
It should be read in conjunction with previous articles ‘Suspended beam and block concrete floors – guidance on selection of products and materials’ TE15, October 2014 and ‘Structural reinforced in-situ concrete toppings for use with beam and block suspended ground floors in residential construction’ TE20, April 2016. Further reference should also be made to the MPA British Precast Flooring Federation ‘Application Guide for the Specification and Installation of Concrete Toppings to Beam & EPS Block Suspended Floors’, September 2017.
Structural fibre reinforcements (be it steel fibres to BS EN 14889-1 or Class II polymer macro fibres to BS EN 14889-2, with both needing to be certified for structural uses in concrete mortar or grout) have different properties and structural characteristics. They are also applied at different dosage rates in in-situ concrete toppings to beam and block suspended ground floors, as identified on relevant flooring system or fibre independent technical approval body assessments accepted by NHBC.
These assessments will also identify relevant concrete mix design requirements appropriate to the assessment, however there is still potential for variability of mix constituents.
Because of the permutations and varied magnitudes of reinforcement provided by the different structural fibres, it is difficult to predict performance with respect to mitigating cracks occurring in relatively young structural fibre reinforced concrete due to plastic or drying shrinkage.
If not properly considered, cracks or cracking could still develop to an extent whereby structural remedial work is required to reinstate the toppings integrity.
It is possible to mitigate potential for this occurring by not only referring to published industry guidance and guidance provided on assessments relative to the practical aspects and bearing in mind pour layouts, sizes, joints, curing techniques, etc., but also by seeking advice from fibre and concrete producers and suppliers as well as Chartered Engineers.
Technical and construction directors and managers, architects, designers, fibre and concrete producers, specifiers and purchasers and site managers.
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