Durability of Cement.

Gisborne Standard and Cook County Gazette, Volume I, Issue 44, 22 September 1887, Page 4

Durability of Cement.

Tax following letter appears in the New Zealand Herald •' —Sir, —The following disclosure,{which I came across it a Scotch paper recently received, may prove somewhat interesting to your reader* in connection with Auckland’* lateat, and I may say, greatest triumph, the Calliope Dock i —“ A ; matter of the highest possible importance and interest to all connected with the construction and management of harbour* has been brought to light at Aberbeen Two year* since the Aberdeen Harbour Commissioners opened a graving dock. The dock was formed of Portland cement concrete, ’he step* being lined with granite a*hA few month* ago it was noticed ‘ tha "oncrete entrance walls, which tnattne , w j tll g ran j te be Cotne to the cause wa* at once • Smith, the harbour engineer, suL’Pecting that chemical action was inducing >ne mischief, conferred with Professor Brazier, of Aberdeen University, who analysed briquettes of the Portland cement used in the construction of the ■raving dock, and also sample* of the concrete taken from the entrance walls of the dock. From the analysis made it appeared that the action of the ■eawater on the Portland cement

itself, as well as on the cement in the concrete, caused an expansion and softening of the cement in consequence of the deposit of magnesia from the seawater, and also led to the formation of carbonate of lime by the union of the carbonic acid contained in the seawater with the lime in the cement. The somewhat startling discovery must necessarily receive great attention. Within the past quarter of a century a great number of sea work* have been formed of Portland cement concrete. At Aberdeen itself there i* a breakwater of nearly a thousand JtcetJJsntirely of concrete. In various ways ithas required patching since its construction fifteen year* ago, but the idea that it* defects were due to chemical action did not occur to the harbour engineer till last year. Now that science has been called in, and has made the discovery that concrete must give way before the sea, it will be the task of chemists to look out for some counteravailing substance which shall prevent the decay that seems to be inevitable.” We may congratulate ourselves on the fact that Auckland’s dock is well provided with granite entrance walls; and the concrete in the interior, not being continually in contact witn the sea water, should be able to withstand the chemical action for a long time. If decay should make its appearance, however, it would be well to pay attention to the foregoing discovery and find out whether a preventative chemical has come to light.—l am, &c. J. Gosjon Lo&Ak. Auckland, September 15,1887.