USE OF MINERAL IN CONCRETE

Press, Volume LXXXIX, Issue 27010, 9 April 1953, Page 11

USE OF MINERAL IN CONCRETE

FURTHER TESTING FAVOURED (New Zealand Press Association) AUCKLAND, April 8. Further testing would be required before the advantages of pozzolanic mineral in the local manufacture of concrete could be determined, said Mr H. W. Cormack, of Auckland, chairman of the cement and concrete committee of the New Zealand Standards Institute, in a statement today. “Pozzolanas have been known for many years,” said Mr Cormack, ‘‘and were in fact used by the early Romans. Without doubt they offer many advantages in concrete, mostly in the form of lower evolution of heat upon setting, a great virtue in dam construction. ‘‘However, it is characteristic of pozzolanas in concrete that they give a much lower strength at early ages—say, up to two months—than does conventional concrete. As it is strength at early ages that mostly determines the use of concrete in building construction, it is doubtful whether the use of pozzolanas in that particular direction will be of great benefit. On the other hand, it might be quite different in heavy construction, such as dams.” Mr T. N. Arnold, of Auckland, con-sulting-engineer to Engineering Minerals (N.Z.), Ltd., said that New Zealand materials were as good as any in the world and should be used, and that pozzolana make a better quality cement. He agreed with Mr E. Leese, of Wilsons Portland Cement, Ltd., that caution should be used in incorporating pozzolanas in major concrete structures, but disagreed that pozzolanas were unpredictable, injurious to concrete, complicated to use, or that they were all slow hardening, as Mr Leese asserted. He pointed to Hitler’s autobahns and to major concrete structures in. America as examples of the successful use of pozzolanic materials in major works.