THE TRUTH ABOUT CONCRETE.

Auckland Star, Volume XXXIX, Issue 234, 30 September 1908, Page 8

THE TRUTH ABOUT CONCRETE.

(To the Editor.) • Sir, —I noticed a letter in last Wednesday's "Star" on concrete, signed Jno. Guiniven, which gives a wrong impression about concrete. The writer says "that if a chip is broken off a pile, a dab of cement will make it as good as ever." And again, "One point 1 would put emphasis on, and that is in concrete work any defect can be easily repaired." I cannot allow this statement to go I forth to the world unchallenged, because ii believe Mr Guiniven is mistaken; and | that, as a matter of fact, there is nothI ing more difficult to repair than broken l concrete, and it is practically impossible to get any strength at the joining, for. when concrete gets old, there is no suction in it, and consequently the new work will not grip or unite to the old. To give an instance—l watched men the other day taking up part of Queen-street to effect repairs. The original formation was cement concrete, and upon that about two inches of fine stuff had been added, no doubt to get a regular sirr- , face to receive the asphalte, and this two inches of stuff came away in one flake; it was quite loose, and plainly had never been attached to the concrete below at all, yet that work could not have been very old or dry. It has been affirmed that 1§ inch of concrete, made 4 to 1, would be impervious to water, and. if that is so, how could there be suction sufficient to cause the nevr concrete to set to the old, or to unite with it? And as to that "dab of cement," Mr Powell reported to the board that repairs effected two months only were breaking out again. That shows the value of the dab of cement; it also proves my statement of the case. For there is no doubt in my mind that the defects showing at the junctions of braces, etc., and the failure of repairs to stand, is due or owing to, that inherent defect which I have mentioned in the nature of concrete itself; and not to the action of rust at all. I do not mean by this that the rust will not break off the concrete, but only that I think it would take more time. It is no doubt the same with regard to the cracks showing in the piles. I suspect the thin part has been shaken in the driving, and the rust stains are running through the cracks, but I doubt if the' rust has caused the cracks, although I may be herein mistaken. I think, as T have said before, it would take more time to operate. However that may be, the rust is a very powerful thing, and the proposal to scrape it off and effect repairs would be laughable were it not so serious. Let anyone interested in this matter (which should include everyone) take a walk down and look at the mass of steel rods and wires exposed on i

the east side of the new Queen-street wharf. They are covered with rust; and it is obvious that the steel must of necessity be always exposed during the progress of the work. It is not pleasant to have to write in this manner, and. I may be thought to be a "Job's comforter," but I believe that I have written nothing but the truth; that truth is best always, and the sooner it is recognised the better, in this instance, for all concerned.—l am, etc., Win. PHILCOX.