Ready-mix Concrete
Concrete Quality Policy
Scribante Concrete supplies concrete in accordance to the requirements set out in SANS 878:2003. This specification covers all aspects of the production of Readymix concrete and encompasses the requirements of SANS 1083. In addition, Scribante Concrete is SARMA accredited and guarantees the attainment of the 28-day specified strength of all concrete supplied. This is provided the contractor follows all the correct work methods and testing whilst receiving, placing, compacting and finishing the concrete.
To define the processes of sampling and testing of raw materials and concrete products:
Process control testing:Â Slump and compressive strength tests carried out in accordance with relevant SANS Standard Test Methods on randomly selected loads of concrete in order to validate product quality, in accordance with the sampling protocol.
Sampling protocol:Â This defines the frequency for taking samples of fresh concrete for slump testing (as set out in this procedure) and for the preparation of cubes for compressive strength testing.
Sample: This is defined by SANS 878:2004.
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Our Protocol for sampling for testing
Samples are linked to a plant but are largely taken at site so that each day, the site sampling frequency conforms to the requirements shown in Table 1.
Table 1: Sampling protocol
Total daily production | No. of samples to be taken and tested |
|---|---|
0 to 50 m3/day | One sample per 50 m3 of total concrete production for that plant and 1 sample for every 100m3 thereafter. |
The Quality team checks actual number of samples taken and recorded against the above sampling rate, and follows up with appropriate corrective/preventive action when the sampling frequency requirements given above are not met.
Sampling concrete
Fresh concrete for slump tests and for making concrete cubes is sampled in accordance with SANS 5861-2:1994.Â
Samples are protected from drying out, and transported, if necessary, in such a way that segregation is avoided, ie. in closed buckets on rubber matting in the back of the vehicle.
TESTS
Slump Test
Slump tests are carried out in accordance with SANS 5862:1994 in accordance with sampling frequency as given in para above. In addition, slump tests may be carried out on site where required by the customer.
Prior to sampling, the concrete is thoroughly mixed, typically at 12 to 15 revolutions per minute (at least) using the stop/start method.
Results of these tests are recorded on a Cube Data Sheet
The results are immediately reported by the sampler to:
- The Batcher for adjustment of the load if required.
- The responsible quality staff member who follows-up all non conformance.
Cube Tests
Samples are taken from loads in accordance with sampling frequency given in para above.
Making, curing and storage of cubes is in accordance with SANS 5861-3:1994.
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Raw materials (technical requirements)
General
The Quality department sets limits for the properties of different raw materials, and is responsible for assessing raw materials for compliance with technical and quality requirements.
Cementitious materials and admixtures
Cements, cementitious materials and admixtures are tested by the supplier, using a standard concrete mix. Test results or Certificates of Compliance are supplied to the Quality Managers when supplier production processes may affect material properties. Results are assessed by the Quality Manager/or relevant technical Staff member for compliance.
Aggregates
Coarse aggregate (stone) and fine aggregate (sand) for stockpiles/bins at Concrete plants are tested every week by Scribante Concrete in accordance with SANS Standard Test Methods 197, 201 and 5847:1994 for compliance with SANS 1083:2002 and Scribante Concrete specifications.
Non-conformances
Where raw materials are tested as above and found to be non-compliant with specification or other requirements, the tester reports the non-conformance to the Quality department.
Analysis of raw material properties
The Quality Manager/or relevant Quality Staff member:
- Checks the databases/programmes regularly for non-conformities or deviances
- Reports these directly to the supplier.
- Agrees on preventive action with the supplier.
- Follows up on agreed action.
If changes to the properties of raw materials continue for an indefinite period:
- The Quality Manager modifies mix designs for the affected plant to accommodate the changes.
