CCANZ News

Cement Update

26 Jan 2015

Integrity of Cement and Concrete Standard Upheld

CCANZ continues to work with cement and concrete industry players to ensure that cement and concrete with elevated alkali levels is not distributed in New Zealand for uses where it would breach standards.

Rob Gaimster, chief executive of the Cement and Concrete Association of New Zealand (CCANZ) says that “a series of investigations into some specific allegations of high alkali cement have determined that there are no reasonable grounds to believe that cement was supplied into the market which did not meet New Zealand standards.”

“Publicity arose this year suggesting that some imports of cement had excessive levels of alkali and therefore had affected concrete manufactured using the cement. The allegation was that this cement put buildings using that concrete at risk of what is sometimes referred to as “concrete cancer” (Alkali Silica Reaction or ASR).”

“The Plant Audit Committee, an independent group of concrete professional specialists, which oversees 170 ready mix concrete plants in New Zealand, determined that concrete manufactured using the cement in question complied with the requirements of the standard for minimising ASR (CCANZ TR 3).”

“An independent consultant’s report into the supply of the imported cement in question concluded that the cement did not have excessive alkali levels and that the series of tests which showed elevated levels and created the initial confusion arose because of deficiencies in sampling techniques. The cement manufacturer’s official tests were covered by international third party accreditation and demonstrated that cement in question had alkali levels within the normal range.”

“It confirms our belief that any risks associated with high alkali cement have been thoroughly understood by the industry for decades, and are managed appropriately at the concrete manufacturing end of the industry. Concrete is manufactured to rigorous standards to ensure alkali levels are managed, and concrete plants are subjected to an audit process for compliance with the NZ Standard 3104 Specification for Concrete Production.”

“A key role of CCANZ is to deliver successful industry solutions based on technical expertise. In this instance the technical expertise of the industry has been shown to be rigorous and protects all stakeholders including the public who use the buildings constructed with concrete. Concrete is a leading sustainable material of choice for the built environment.”

“We are vitally concerned when there is any suggestion that the integrity of the industry could be brought into question and pleased that the independent reports have upheld the integrity of our industry. Throughout this process we have been updating MBIE, the regulator, on the information we have had at hand while the independent experts were researching and producing their reports,” said Chief Executive Rob Gaimster.

Prior to this issue, a review of the Standard for cement (NZS 3122) recommended the inclusion of a specific clause for alkali levels and sampling which will have to be undertaken in New Zealand in future. If the new Standard had been in force at the time, the sampling for the tests would have been done differently, thus preventing the confusion. 

Contact – Rob Gaimster, 021 928 651

Reports
The report of the Plant Audit Committee including the consultant’s report is available upon request from CCANZ - email admin@ccanz.org.nz 

About Alkali Silica Reaction
Under specific circumstances, concrete made with high alkali cement can create a problem called Alkali Silica Reaction (ASR) when used in conjunction with some aggregates containing reactive silica.

The reaction that occurs can cause concrete to expand and crack.  This occurs over a long period of time.

In order for ASR to occur, a range of factors need to co-exist which include the use of reactive aggregates, sufficiently high reactive alkali hydroxide concentrations and a sufficient source of regularly present moisture.

ASR has been a very well understood and managed matter in the cement and concrete industry internationally and in New Zealand for many years.

Download this Update as a pdf.