Following on from the review of publication S.R. 21:2014 to deal with the issues arising from Pyrite and the properties of aggregates for use in unbound and hydraulically bound materials, there has been revisions to Annex E and the recommendations for procedures for production of unbound granular fill (commonly known as hardcore) for use under concrete floors and footpaths.
The main changes to S.R. 21:2014 Annex E are in the following areas:
- Material Properties
- Geological description
- Total Sulfur
- Geological and petrographic assessment. More explicit guidance is given on the geological and petrographic assessment to limit the risk of swelling due to the potential presence of a reactive form of pyrite.
- Factory Production Control. The minimum test frequencies as specified in Annex C of I.S. EN 13242:2002+A1:2007 for some properties are increased in order to improve confidence within the supply chain.
- The System of assessment and verification of constancy of performance (AVCP) has changed from system 4 to system 2+ for this particular end use aggregates.
- Documentation. The intended use of this aggregate should be clearly stated on the Declaration of Performance, and other documentation.
4 Types of Hardcore/Grading (under concrete)
- T0 Structural – 0-125mm for use >900 below damp proof membrane (DPM);
- T1 Structural – 0-32mm crushed rock or 0-40mm crushed gravel for use beneath DPM and as far below DPM as required (unless T0 preferred lower down);
- T2 Permerable – 4-40mm gas permeable material of which a 200mm layer must be used where a radon sump is used (greater depth allowable if preferred to mixing gradings with T1 Struc): and
- T3 Blinding – a 0-4mm blinding for immediately under the DPM regardless of what hardcore choice has been made to that point.