BUILDING

Evening Post, Volume CXVIII, Issue 96, 20 October 1934, Page 9

BUILDING

THE AID OF SCIENCE

RECENT DISCOVERIES

EXHIBITS AT OLYMPIA.

(From "The Post's" Representative.) LONDON, September 14.

A very interesting section of the Building Exhibition now in progress is that arranged by the Department of Scientific and Industrial Research. Most ■useful work has been carried on for a number of years at tho Building Research Station at Garston, near Watford, and also at tho Forest Products Research Laboratory at Princes Risborough. How extensive the work has been may be seen from a list of about 150 pamphlets published on the widest possible range of subjects. The exhibit covers work on structural stool, plain and reinforced concrete, cement, and cement' products, natural stone limetp and plasters, brick and timber, codes of practice for the use of certain of theso materials in construction, and aspects of construction, heating, and lighting involved in securing comfortable conditions in a building. Borne of the less technical demonstrations are especially interesting to the home builder and the genera] public. Experimental double roofs, for instance, showing that while such a roof, without reflecting surfacos of any kind, allows a heat of 140dog.F. to pass through, the same roof with tho proper reflecting surfaces allows only 70dcg. F. to pass through. While, tho co-eili-cient of a doublo wall without reflecting surfaces is 0.50, tho co-cfticiont for a doublo wall with an aluminium foil midway in the air spaeo is only 0.18. A SIMPLE REMEDY. Then the question of sunlight is being carefully considered. The heliodon is an instrument which enables an architect to predetermine the incidence of sunlight in any room at any hour of the day or time of the year. An electric light acts as the sun, and a model of the house or other building is placed on a scaled platform, which can be moved into any position to represent the position of the house in relation to tho sun at any hour of the day or time of the year. In short, instead of the sun apparently moving round the house, tho house moves round the sun. The occurrence of great blisters on bituminous material laid on flat concrete roofs has been inquired into. It has been found that a spot of watei between the adhesive substance and the concrete roof is enough to raise these blisters. The remedy is a simple one— to lay a sheet of brown paper between the substance and the roof and so break the adhesion altogether. Dust streaks often appear on ceilings, following the course of tho beams and laths beneath them. It has been found that these streaks occur when there is a cold room above. Dust has a habit of bombarding tho colder parts of a surface more intensely than tho warmor parts, and as the particles settle preferentially on tho cooler surfaces of the plaster the pattorns reproduce the areas differing in temperature. A wholly effective mothod of obviating this fault has not yet been found, but the research workers have gone so far as to change the markings into a honeycomb pattern instead of a streaky pattern. PROPERTIES OP BRICKS. The mechanical properties of the clay bricks normally used in building construction are usually more than adequate for -the service required of thorn. The physico-chemical properties of the clay product, however, may influence tho appearance and even tho durability of the masonry in which they aro incorporated. Soluble salts, either produced in the brick during the liring, or derived from the mortar bonding, may lead to the appearance of unsightly efflorescences, and under certain extrouio conditions may cause disruption of the brick'and dislodgement of attached renderings and plasters. In connection with exploratory work in this field, a study is being made at tho Building Research Station of the effect of variation of firing conditions on the soluble salt content and other properties of typical clays. As a general rule, it is found that the higher temperature the firing tho less the efflorescences. London stone buildings always turn black in time owing to the sulphur in tho air from the coal smoke. In some cases the stone is broken away by the chemical action. The research station has a simple but effective remedy which is followed by several owners of stone buildings. It -employs tho fire brigado to hose the building down twice a year. Once the stone ia cleaned up—probably with a steam plant—tho hosing is enough to keep, it clean. THE DRIVING OF PILES. The stresses set up during the driving of a reinforced concrete pile are probably the highest encountered during its life, and tho possibility of failure at some point along its length has often to be faced. At tho instance and with the support of tho Federation of Civil Engineering Contractors, research is in progress to ascertain the conditions of driving undor Which such failure is likely to occur. For this work a piezo-elec-trie (quartz) stress recorder has been developed which, with gauges cast in tho pile at selected points, enables complete records to bo obtained of tho trimsitory impact stresses sot up by the blow. The modol pile-driver may bo seen in action, and when the blow is struck tho oscillation of the Cathode ray may be seen. In serious work this zig-zagging spark is'photographed and the danger point of the oscillation is known. Another interesting instrument is the oupatheoseope, a vessel which reacts to temperatures just liko a clothed human being. "With this instrument one may measure the temperatures as they affect human beings in a room, and thus make rearrangements for comfort. Finally, tho apparatus for measuring stresses and strains on buildings and bridges is most ingenious. A little instrument contains a wire stretched over two knife edgos. The instrument is clamped tight to any part of tho steel structure, or many instruments may bo used. By an electric devico tho wire is made to sound a note, and this note is carried by telephono to tho ear of thfi observer. When tho strain is put on the structure the noto rises in pitch. A note on an instrument in the enginoer Js room is made to harmonise exactly with the note sent in by message, and then tho instrument records tho amount of stress endured. _______________