Rules for Concrete Construction.

Progress, Volume II, Issue 2, 1 December 1906, Page 46

Rules for Concrete Construction.

The National Board of Fire Underwriters in America have prepared, through their Committee ort Construction of Buildings, a building code, designed to secure uniform building laws throughout the country. In the course of the Committee's report relating to this code some remarks are made about concrete construction which are likely to be of interest to the building trade in this country as well as in America. Numerous inquiries regarding concrete construe-

in the process of hardening, or setting, as it is called ; the disintegration being due to the expansive force of ice. In the use of concrete constructed walls a variety of constructions have to be considered , solid concrete, hollow blocks of concrete, where the voids or spaces are as great or greater than the solid material, concrete combined with wire cloth or bars, commonly termed reinforced concrete, many of such devices being patented, and involving serious questions as to the proper allowance of strength to be given to the iron and to the concrete when the two are united. It will be seen therefore that the task of formulating exact regulations for concrete construction is very difficult if not impossible. The National Board Code provides for the proper use of cement combined with other materials as far as the same are known or have been tested by authorities, although such tests have not included the supreme test of time, long outdoor exposure or fire or water — or all of these combined. Nature's verdict is often different from man's. The quality of cement that shall be used in the construction of buildings the mixture and kind of materials m making mortar and concrete, its use and thickness for various purposes, including the filling of spaces between floor beams, are fully and properly set forth. For reinforced concrete or concrete steel constructed buildings the code contains elaborate requirements believed to correctly embody the best known practice of to-day for this branch of the art of building. The entire code needs to be carefully and con-

tion (says the committee) by members of the Board and others lead the committee to attempt a word by way of explanation .—. — Cement is recognised all over the civilised world as one of the most valuable adjuncts in building operations. Its manufacture has assumed vast proproportions in New Zealand within a comparatively few years. In the construction of buildings, from cement and sand mixed being used for mortar in laying up stone and brick walls, or cement and sand and broken stone mixed being used as concrete for footings of walls and piers, the use of cement with other aggregates has enormously increased within the past fifteen or twenty years for floor filling between steel beams, for partitions, and still more recently for outer walls, The great danger to be apprehended from the use of cement combined with other materials is its commercial mixture, and its use in freezing weather. With the best materials, good cement, clean, sharp sand of proper size sand grains, and small, clean, broken stone or gravel, become the careless or improper mixture of the several parts, in the hurry of building operations, the mixing being done more frequently by unskilled labour than by machinery In cases where the mixture includes cement, ashes, cinders, and clinkers, or other partially carbonised material, with possibly some sand, the ashes frequently contain refuse vegetable matter, and these aggregates often being carelessly mixed, the result is an utterly unreliable product. Good and poor cement mixtures are alike affected in very cold weather by the free water in the mixture freezing before it becomes combined by crystallisation

stantly watched and bettered as future experience may, and undoubtedly will, teach, but in perhaps no particular is more care and attention demanded than m matters relating to concrete construction and artificial mixtures. The committee is of the opinion that until the merits of concrete construction are more firmly established, it will be unwise to make any change in the code.