FERRO-CONCRETE WHARVES.

Auckland Star, Volume XXXIX, Issue 233, 29 September 1908, Page 5

FERRO-CONCRETE WHARVES.

LETTER FROM MR HAMER. At 2.30 o'clock this afternoon the members of the Harbour Board assembled on the wharf for the purpose of personally inspecting some ferro-concrete piles .that have been drawn, and which were reported to be a good test of durability, as they were amongst some of the first put in. - In connection with the question of the stability of ferro-concrete structures and dangers of oxidisation, an interesting letter has been received by the Board from Mr Hamer (Ekigineer to the Board), at present on a trip to the old cdhntry. It is in answer to communications forwarded regarding signs of rust on the railway wharf, and reads as follows-.— "I received your cable of Ist on August 6, as London offices were closed from Friday to Tuesday over the August Bank Holiday. I was then leaving with Mr Andrews for Glasgow re new tug, and to inspect the Northern ports. The en- ' gineer at Southampton was away, and I bad to change date of visit there. I visited all Canadian and American East Cost ports, and arrived in London on July 23. I have since visited Bristol, Glasgow, Aberdeen, Dundee, Newcastle-on-Tyne, North and ith Shields, Hull, Immingham new dock, and Grimsby, in addition to some London docks. I visit the South Wales, German, and Dutch ports later. Together with Mr Andrews and our agents, I have gone into the question of tenders received for capstans, stationary dredger, bucket dredger, floating crane, which has involved many days' careful work and enquiry. I have to-day asked agents to cable in reply to yours. I desire to see other works before replying, but will report on those later. I only found one case of oxidisation, and that only local on the underside corners of the deck beams, five feet above high water. It was caused by rather larger stones than usual getting under the lower bars in the framing, and not being properly filled in between. These defects were easily remedied. . I have not been able to discover any trouble in the great length of quays I have seen below the high-water mark. It all looked clean, and sound, and good. There have been three cases of large vessels running end-on into jetties, and repairs were easily and satisfactorily effected. I find extensions in this work being carried on, and recommended everywhere. Where I noticed small rust marks, I carefully inspected, and mostly they were nails from the timber framing; in any case, they were considered quite immaterial, and small patches were In places cut out and repointed. . In America and Canada I found concrete ; piles being substituted for timber. In New York all decking is reinforced con- ' crote, on wooden piles. There is no teredo there, hut the engineer has suggested that the authorities must now consider concrete piles, and says that no more timber will be put in. I regret that ' you should find anything to be unsatis- ' factory in our pile work, but it would ' astonish mc if in such large areas there ' were not some defects to attend to. It is hardly possible to construct such - areas by human means without some ' defects, but I cannot think they are serious or more than local, and they can be easily adjusted. The cause is either a few larger stones collecting in the j framing, near rods, or compressed air forming hubbies when ramming. Such ' places should be cut_ out, cleaned, and : pointed with .rich cement mortar. Rust , marks here and there that I have chipped were certainly never dangerous or ' serious. I want you to have the best, ' and wish you could afford solid walls, but it seems out of the question, and ' would certainly be difficult. As I have : said before, and it is obvious, that it is ' not material to mc if you prefer timber, but I think you are right now, and will < always recommend solid permanent work ' where it can be economically applied." The pile under examination this afternoon was one of the fiiat made by the company, and bad been in use 4_ years. It was placed in a situation where it ' was bumped by logs, and as a result ■ the corners bad been knocked off to a certain extent; but all the same, when the men set to work with sledge hammers ' to knock away the concrete and expose the iron rods, it was found that there i was comparatively little oxidisation excepting nt ope or two points, where, on the surface, it showed that there had been a small hole which had admitted the water. Mr. Moore, engineer to the company, said that it was impossible for a human being make anything absolutely perfect, but still he contended that the example shown the Board proved that good work had been done. He also said that he had calculated it out, and found that if . .all the steel rusted away there wonld ' still remain a permanent structure of ferro-concrete. "You are getting," said Mr. Moore, "a . .good wharf that can be easily repaired, 'and it is costing you less than a wooden structure." Mr. Powell, engineer, ex- ■ pressed himself that the test was a •thoroughly satisfactory one. He also showed to the members the natural cement formation on the rods, which, when the work is properly done, should preserve it against any danger of oxidisation in the future.