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Contractor (June 2015) Strong Standards For A Strong Industry

01 Jun 2015
Rob Gaimster
Cement & Concrete Association (CCANZ)

The effective functioning of the concrete industry and wider construction sector is based to a huge degree on robust New Zealand Standards.

These are developed through industry accord to create documents that instruct best practice, describe performance boundaries and offer compliance guidance through the construction regulatory framework.

Although the monitoring of Standards for currency is an ongoing undertaking, the concrete industry is busier than usual at the moment, updating a range of important documents across both Industry Standards and New Zealand Standards.

INDUSTRY STANDARDS

There are a number of industry best practice documents which by being referenced in the New Zealand Building Code (NZBC) become Industry Standards.

For instance, the recently revised CCANZ publication Code of Practice for Weathertight Concrete and Concrete Masonry Construction (CP 01:2014) is cited as Acceptable Solution 3 of the NZBC Clause E2 External Moisture.

Similarly, the NZBC cited CCANZ Technical Report 3 Alkali Silica Reaction: Minimising the Risk of Damage to Concrete - Guidance Notes and Recommended Practice is being considered for review.

NZ CEMENT STANDARD

New Zealand’s cement Standard, NZS 3122 Specification for Portland and Blended Cements (General and Special Purpose) was amended in December 2014.

The amendments reinforce the requirements for cement through (i) a provision to restrict the total alkali content and (ii) new requirements for sampling and testing. 

In terms of controlling the total alkali content NZS 3122 includes a requirement expressed as sodium (Na2O) equivalent for type GP (General Purpose) and HE (High Early strength) cement. 

Aggregates susceptible to the potentially deleterious effects of Alkali Silica Reaction (ASR) exist in certain parts of New Zealand. Provisions for minimising the risk of ASR are given in the CCANZ publication TR3, one of which is limiting the maximum total concrete alkali content when potentially reactive aggregates are used. NZS 3122 now sets a limit of 0.6% or less.

Interestingly, where there is specific prior agreement and notification of the purchaser or cement user, the cement manufacturer or supplier may supply cement which exceeds this maximum alkali limit. It should be remembered that where aggregates which are deemed to be non-reactive are used, no precautions are necessary in terms of ASR. 

Sampling and testing frequencies are now in NZS 3122. There were no provisions in the previous version, although it should be stressed that the two cement companies, Golden Bay Cement and Holcim (NZ) Ltd, which have historically supplied the lion’s share of New Zealand cement, have always tested and reported routinely.

Furthermore, it is a new requirement that all cement sampling be undertaken at the point of entry prior to distribution. This ensures complete traceability between the cement consignment and its certification. It is also a requirement that any cement supplied out of sample date shall be subject to re-sample and re-test by the supplier.

NZS 3122 now also gives minimum sampling and testing frequencies for ‘proven’ and ‘unproven’ sources. A source is proven where there is at least six months of data obtained in accordance with NZS 3122. All testing has to be undertaken by a laboratory independently accredited by a member of the International Laboratory Accreditation Cooperation.

As in previous versions of NZS 3122, cement properties are classified as ‘specified’ or ‘reportable’. Of the eight reportable properties, the supplier will report test results as nominated by the purchaser or user. The supplier does not have to provide the reportable properties unless requested.

OTHER NZ CONCRETE STANDARDS

Another important Standard under review is NZS 3121 Specification for Water and Aggregate for Concrete, which gives essential requirements for water and aggregates, other than lightweight aggregates, suitable for use as materials for making concrete to meet normal structural and durability requirements.

NZS 3101 Concrete Structures Standard is also under review. Part One, The Design of Concrete Structures, specifies minimum requirements for the design of reinforced and pre-stressed concrete structures. Part Two, Commentary on The Design of Concrete Structures, explains the provisions of Part One, summarises technical background and suggests approaches which satisfy the intent of the Standard.

Progressing alongside NZS 3101 is the review of NZS 1170.5 Structural Design Actions - Part 5: Earthquake Actions - New Zealand, which provides procedures for the determination of earthquake actions on structures in New Zealand. It gives the requirements for verification procedures, site hazard determination, the evaluation of structural characteristics, structural analysis for earthquake action effects, the determination and limits for deformations and the seismic design of parts of structures.

FUTURE STANDARDS MODEL

Standards development is currently under going change in New Zealand, with the Ministry of Business, Innovation and Employment’s (MBIE) Standards & Conformance Review and subsequent Standards Bill driving through a number of governance, administration and funding modifications.

Regardless of the eventual model, Standards will remain a vitally important tool in ensuring quality construction, one which the wider concrete industry remains firmly committed to.

Article appeared in Contractor magazine.