THE CEMENT AGE

Taranaki Daily News, 6 September 1929, Page 15

THE CEMENT AGE

GROWTH OF OUTPUTS.

NEW ZEALAND STANDARD HIGH,

(From Our Own Correspondent.) Wellington, Sept.' 3. Professor C. H. Reilly, who has occupied the Chair of Architectureat the University of Liverpool since 1904, considers that we are at the dawn of a new era so far as building construction is concerned, ferro-concrete being employed for all types of building work through the world, irrespective of climatic conditions. The constant use of ferro-concrete has had the result of increasing the world demand for, cement enormously. In England many cement works have had to increase their oiitput within recent years. A typical mstapV is tho Tunnel Cement Works on the Thames, near Tilbury, whose output at the present time is approximately 2ol),000 tons per annum, double the output of four years ago. This, is said to be due largely to the increasing demand tor British cement in Empire markets.where uniform high quality is essential. . The professor states that great strides have been made in recent years towards improving the quality and hastening the hardening properties of Portland cement. Not many years ago the British engineering standard specification for Portland cement allowed a residue of 14 per cent, on a sieve 32,400 meshes to the square inch. In 1925 this specification was revised, and only 10 per cent, residue is now permissible on thesame small sieve. Most British brands of cement are well within this limit. Tunnelite rapid hardening cement, for instance, Shows a residue of only 1 per cent. It - is the extreme fineness of this brand which contributes very largely towards its rapid hardening qualities. Concrete made with tunnelite possesses the same strength after two days as ordinary Portland cement concrete does after seven days. The quick hardening enables building operations to be carried out expeditiously, and thereby costs are reduced.

It is distinctly encouraging to find that the . .cement manufactured in New Zealand is up to the world standard; as a matter of fact in recent years Nevj Zealand has progressed similarly- with England in regard to cement quality. The British standard specification is used as the standard of guarantee in this Dominion, whereas in Australia - a local specification, which includes the mechanical ramming of test pieces, is .in force.

There are three cement companies operating in New Zealand, two in the South Island and one in the North.'Both wet and dry systems are in use; the latest machinery and methods are adopt-; ed, and the projects manufactured are very ’well thought of. The capacity of the existing plants is said to be greater' th :i the demand. Portland cement, rapid • hardening Portland cement and hydraulic lime are the products manufactured and supplied, the latter being made continuously in rotary kilns, concurrently with tho production of cement clinker.

Ordinary Portland cement of to-day has improved in quality enormously.: Since 1927 all the cement made in New Zealand is of a quality which at- 24 hours is as hard as that produced in 1919 was at seven days. Similarly the three-day Hardness old cement manufactured from 1927 onwards is greater than the hardness in 28 days of the' cement ~ produced in 1919. Rapid hardening / Portland cements, introduced locally some years ago, give strength and hardness in three days as great, if not greater than, present day Portland < cements attain in 28 days. This type of cement has received favourable sup- ; .< port for speedy work, and reinforced : concrete piles have been • successfully driven in live and seven days after mixmg on important and large structures. Independent tests carried out overseas of New Zealand made rapid hardening , cement have demonstrated that it is ' equal to the best grades of similar hydraulic cements manufactured in Europe and America. . '