Sampling and testing decoiled material
A significant proportion of the reinforcing steel manufactured by steel mills and processed by reinforcement fabricators, both in the UK and worldwide, is in the form of coiled product. This is particularly so for diameters between 6mm to 16mm. This product is then ‘decoiled’ on automatic cutting and bending machines, which decoil, straighten and cut or bend and cut depending on the particular shape required. Such decoiling, dependent upon the process route that the steel mills used in its manufacture and the type of decoiling machine used by the reinforcement fabricator, may alter the geometrical and mechanical properties of the material to a greater or lesser extent. CARES certification deals with this possibility, in order to ensure that the risk of non-complying steel reaching the construction site is reduced.
This information sheet provides guidance on the requirement for the sampling and testing of decoiled material. The European Standard for Reinforcing Steel, EN10080, and hence the associated British Standard BS4449, place the responsibility for compliance with the properties of decoiled material with the processor of that material. The CARES Steel for the Reinforcement of Concrete Scheme manual takes this into account. It is addressed in Appendix 2 – 2.4 vi which states that ‘the processor shall operate a documented procedure which assures that all decoiled material continues to meet the dimensional and standard mechanical property requirements of the relevant British Standard’. Mechanical testing, which forms part of this procedure, shall be performed in a UKAS (NAMAS) approved laboratory or a CARES approved company.
Bearing in mind the requirements of EN 10080, CARES has adopted a pragmatic approach to the sampling and testing of decoiled material. Each fabricator shall be responsible for developing and implementing a procedure that identifies and addresses the key variables of the process. There are two generic decoiling processes, ‘spinner’ and ‘roller’ straightening, for the decoiling of reinforcing bar, in the size range 6 to 16 mm. Other variables that should be considered are the manufacturing process of the steel, i.e. quench and self-tempered, micro alloyed or cold stretched, the diameter of the steel and the machine settings. The procedure shall include mechanical testing at an appropriate frequency to ensure that all decoiled material continues to meet the dimensional and standard mechanical property requirements of the relevant British Standard.
For your information the requirements of BS 4449: 2005 are as follows:
The processor of products produced from coils shall ensure that the decoiled material continues to meet the specified property requirements (mechanical and geometrical) of the appropriate grade of steel.
As a result of the requirements of BS4449 and those of CARES certification the reinforcement fabricator shall operate a documented procedure which shall include the following:
- visual inspection of every coil processed
- for ribbed steel, a surface geometry measurement (rib height or indentation depth) on at least one sample per day and produced size
- Tensile testing at a frequency of at least one sample per machine type (roller or spinner) per week from each of two processed sizes. The sampling shall ensure that all of the machines of the fabricator and all diameters processed are covered in a six month period
Test results shall be evaluated for compliance according to BS4449. For CARES certification, tests shall be performed on the samples at the frequency defined in Table 1. Wherever possible, the CARES tests will coincide with those of the reinforcement fabricator to keep the amount of testing to a minimum, whilst complying with the standard and the CARES rules.
Table 1: Type and number of tests for initial testing and continuous surveillance
|Initial Assessment||Smallest and largest of the diameter range||3 casts per diameter from each coil processing route|
|Surveillance Inspection||One diameter||3 casts per diameter from one coil processing route|
The standard properties defined in Table 2 shall be determined.
Table 2: Testing schedule for standard properties
Number of tests per coil (rod, wire)
|Cross sectional area and mass|
|A5 and Agt|
|Chemistry (inc. CEV)|
|Visual rib inspection|
Further guidance on tensile properties of reinforcing steels is given in Part 3 of the CARES Guide to Reinforcing Steels, which may also be found on this web site.