By John Hambling
President, NZ Ready Mixed Concrete Association
Building quality is topical. The leaky homes debacle has cost homeowners greatly. Indeed cost-effective quality formed a very significant part of the Department of Building and Housing’s (DBH) recent Building Act Review discussion document. Furthermore, product certification has been on DBH’s agenda for sometime.
In terms of product certification, New Zealand consumers of ready mixed concrete can take comfort in the knowledge that concrete produced and supplied by a plant certified under the world-class New Zealand Ready Mixed Concrete Association (NZRMCA) Plant Audit Scheme (PAS) meets high quality standards.
The NZRMCA was formed nearly half a century ago in 1963, and continues to grow in size. Today, 46 companies now control around 185 ready mixed concrete plants throughout New Zealand. Quality control was the prime reason for the formation of the NZRMCA, and in turn the creation of the PAS.
The PAS is available to NZRMCA members, and most avail themselves of the opportunity. Independent of the NZRMCA, the PAS is audited to ISO 9001 by Bureau Veritas Quality International. Full details of the scheme are set up on an independent website: www.cca.org.nz/RMCA/rmca/default.htm.
PAS operates to audit NZRMCA members’ ready mixed concrete plants as defined in the standard, NZS3104 Concrete Production.
The PAS is of great convenience to the specifiers and purchasers of concrete. It provides an independent and rigorous audit of the quality systems in place at a ready mixed concrete plant. Without the scheme, purchasers and specifiers would be faced with a costly and time-consuming audit of concrete quality for each construction project.
When using concrete from non-PAS audited plants, the purchaser is responsible for the implementation of the audit process required by NZS3104 to ensure compliance with NZ Building Code.
PAS operates independently from the management of the NZRMCA both in respect of membership of the plant audit committee and financial matters. Ready mixed concrete plants using the scheme are charged separate fees from any NZRMCA subscriptions. The plant audit committee comprises five or more professional engineers with extensive experience in concrete production.
The establishment and monitoring of the production of a ready mixed plant are requirements for the supply of structural concrete for compliance with NZS3109 Concrete Construction and NZS3104, and in turn the Building Code.
NZS3104 is the standard used by the plant audit committee to audit a ready mixed plant. Compliance with NZS3104 also requires compliance with a number of other Standards, such as NZS3112 Methods of Test for Concrete.
Plants report quality performance data to the committee annually and are subject to a detailed annual review of data, together with an on-site audit every second year. Site audits may also be carried out at any time.
Among performance criteria audited are:
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Mean concrete strengths and coefficients of variation;
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Aggregate quality by testing and monitoring;
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Weigh scale calibration and accuracy;
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Mixer efficiency tests;
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Laboratory equipment calibration;
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Production and testing record keeping;
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Technician training;
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Plant operator performance;
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Effectiveness of plant engineer’s monitoring of quality controls.
In addition to the above, the frequency of testing within each quarter must be submitted to the plant audit committee. Failure to maintain testing requirements can result in the withdrawal of an audit certificate. Performance standards of all plants in the scheme are under regular review. Certificates of audit are issued for a period not exceeding 12 months.
The current status of plants is updated on the PAS website.
Where plants fail to meet the criteria, their audit certificate is removed and noted on the plant list. It is necessary for such plants to resubmit to an initial reassessment with at least 30 results indicating compliance with NZS3104.
Members of the NZRMCA are free to elect to use another authority to classify their plants, and award an audit certificate. Other such authorities work outside the jurisdiction and ISO Certification of the NZRMCA PAS.
The benefits of concrete are well documented. It doesn’t rot for example, is inherently fireproof, is largely maintenance free, extremely durable and in passive solar design affords a significant degree of thermal comfort. So when concrete’s special attributes are coupled with a world-class product assurance scheme, such as the PAS, consumers of ready mixed concrete can take great confidence in their building material.
Contractor Vol.34 No.5 June 2010
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