REINFORCED CONCRETE.

Dominion, Volume 1, Issue 155, 25 March 1908, Page 4

REINFORCED CONCRETE.

ITS USE IN HARBOUR WORKS. Sir, —Being, interested in your description of reinforced concrete in this day's issue, I would liko to call, the l attention of cement users for concrete piles or other cemont work used in • sea water.- Tho quantity of magnesium iu sea,water present- as chloride and sulphate amounts to 0.06 per cent, by weight. In a mass, of eonereto a precipitation of the salts: of magnesia' takes place, some of tho lime 111 tho cemont being dissolved, and these salts of magnesia from the sea water, filling tho interstices of tho concrete, undergo a change' in, volume, producing disintegration and, disruption of tho work. All cemont containing over 5 per cent, of magnesia ought to bo rejected. Care should bo taken that the cement is sound, well burned, and finely ground, gauged with fresh water, especially for piles, and not subjected to tho pressure of a column of sea water for thxoo months aftor gauging." An excess of lime or. magnesia causes disintegration by expansion duo to hydration, and, being soluble, theso substances may bo washed out, leaving the concrete in. a honeycombed state. ' With • regard to tho Destructor chimney, this ought to be allowed to stand unused as long as possible, or the heat mil evaporate the moisture in the cement, and tho hydrogen (which combines with the silica, alumina, and -lime)'will bo gone, and the chemical action wiU'ceaso. —I am, etc., ; . RICHARD HOWLAND. Analyst, and'C-oment Maker. ■ March 23.

CREAT LOSS TO OUR SHiPPIMC TRADE. ' ; Sir, —For ages past England lias spent vast sums of inonoy and lost. thousands of lives in her determination to protect her shipping trado and commorco from loss and destruction by pirates iii 'tho China and other seas. Only recently the German Government has had to pay large sums of money to Burns, Philp, and Co., shipowners of the Commonwealth, for vexatious losses' and delays | incurred by' tho illegal proceedings of officials.in some of the South Sea Islands,''belonging,- to "Germany.As one, deeply interested in tho trado of this port,am.-lUixionSi .to know if tlio strong and up-to-date ..Government now .in office iu the Dominion' will' mako emphatic and • earnest'.'representations to both ; the State Government of New .South' -Wales, arid tho Federal Government 111 Melbourne with reference, .to the vexatious delays'and'serious losses inflicted on. Now Zealand trade and shipping by tho action' of a mere handful of labour trust agitators who "live oil tlio game," in bringing about nud promoting strikes during , tlio last twelve months among the coal miners and wharf hands in Newcastle and Sydney. One of'tho main outlets for our- export and import trades 1 is through Sydnoy and the Commonwealth, and there is every prospect in tho near future that unless very strong representations aro made, by the Dominion Government, our trade and' shipping with and through tho Commonwealth will ..receivo a set-back and shock : that will tako many years to retriove. .

The days of strikes and the power of tho agitator in Wellington and other New .Zealand ports were brought to an end by our Government about ,17 years {ago, and it is high time that, tho, camo .protection was given to our commcrc<?- in- tho ports-of ; tho Commonwealth as tlioy ; 'enjoy in ours, and it is one of th'o most important duties of our Government'to seo that wo get it.' All' tho water frontages, wharves, etc, at, Newcastle belong to tho State Government, and many of tho Sydney wharves and frontages as well, and they are under their , direct control aad management, and should bo held responsible for. all loss and delays incurred. —I am, otc., CITIZEN. Wellington, March 17, 1908.