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Concrete masonry – the silent workhorse

ROB GAIMSTER, CEMENT & CONCRETE ASSOCIATION (CCANZ)

NEW ZEALAND READY MIXED CONCRETE ASSOCIATION (NZRMCA)

I’LL GET STRAIGHT to the point, concrete masonry doesn’t receive the recognition it deserves.

Yet it is a staple material of our construction industry; a silent workhorse that encompasses reinforced concrete block and concrete block veneer, along with concrete block paving and flagstone paving for pedestrian walkways.

The quintessential prefabricated product, it offers designers and builders flexible, robust and affordable solutions across residential, commercial and civil applications.

Let’s take a quick look at the benefits available through the use of concrete masonry, and some of the key resources that enable its uptake.

What’s on offer?

The extended fire protection offered by concrete masonry remains key in fire regulation for various reasons, not least of which is providing a fire barrier that does not contribute to the fire load.

Ironically, the reduction in fire requirements for inter-tenancy walls has led to a growth in sound transmission problems. Despite various competing systems, masonry remains tried and proven.

The weathertight credentials of masonry are enhanced by the fact that it doesn’t rot. Also, industry has moved on from recommending weatherproofing, to providing weathertight details.

While certain concrete masonry applications require assistance to achieve the stipulated R-values, its ability within a passive solar design to trap, store and release the sun’s heat is unquestioned.

The structural environment for concrete masonry has been one of adaptation as and when new structural information, particularly relating to seismic actions, has come to the fore and been expressed in revised regulation.

NZ Concrete Masonry Association (NZCMA)

The development of concrete masonry across New Zealand can be linked to the activities of the NZ Concrete Masonry Association (NZCMA). With its beginnings in 1956, the NZCMA has promoted and offered technical support.

To keep concrete masonry information up to date, the NZCMA works closely with the Cement & Concrete Association of NZ (CCANZ) and with the National Concrete Masonry Association in the USA and the Concrete Masonry Association of Australia.

While the future of the NZCMA forms part of the wider debate about rationalisation across concrete industry associations, its website (www.nzcma.org.nz) offers a range of resources for download.

Concrete Masonry Manual

One such resource is the Concrete Masonry Manual, which was created in the late 1970s as a guide to the design and construction of concrete masonry. Periodically reviewed over the decades as Standards change, the content was last updated in 2013.

Weathertight code of practice

Another resource, one cited by the NZ Building Code as AS3 for Clause E2 External Moisture, CCANZ’s CP 01:2014 – Code of Practice for Weathertight Concrete and Concrete Masonry Construction covers concrete slabs, walls and associated methods of insulation, concrete flat roofs and decks, and concrete to timber construction junctions. A new section has recently been added for masonry veneer.

New Zealand standards

As outlined on the Standards New Zealand website, NZS 4229:2013 Concrete Masonry Buildings Not Requiring Specific Engineering Design provides prescribed methods for the design and construction of reinforced concrete masonry buildings up to 10 metres in height, including domestic dwellings and most other residential buildings, and some commercial buildings.

NZS 4230:2004 Design of Reinforced Concrete Masonry Structures provides information for the design of reinforced concrete masonry structures.

This version recognises the predominant use of reinforced concrete masonry for structural applications, and incorporates research findings specifically pertaining to the performance of reinforced and pre-stressed concrete masonry.

NZS 3116:2002 Concrete Segmental and Flagstone Paving sets out provisions for the non-specific engineering design and construction of pavements using segmental and flagstone pavers. It also provides variations to paver manufacture and tests in relation to Australian cited Standards.

Moving forward

One recent exciting development in concrete masonry has been permeable paving systems, in which slotted blocks allow water to pass between and be processed (ie, self drain) by the base sand and sub-base depending on requirements.

In summary, the New Zealand concrete masonry industry remains focused in its efforts to confront the changes in focus demanded by regulators and customers, and continue to provide resilient solutions.

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