IMPROVING CONCRETE.

Hauraki Plains Gazette, Volume XXXVI, Issue 4873, 4 September 1925, Page 1

IMPROVING CONCRETE.

SILICATE OF SODA PROCESS. ■ VALUE TO FARMERS. The great increase in the use concrete is due largely to 'mprpvements in the technique of the whole process, and one of the most striking examples of this is the simple and inexpensive silicate of soda process for hardening and decreasing the permeability to liquids. The method is of value in almost every one of the multitudinous, uses of concerte, and patricularly in the farming industry, because of the reduction in the permeability to water. It its the object of this article to give the essential factp relating to silicate of soda and concrete, and for further information we should recommend that, application be made to Messrs Brunner Mofld and Co., Ltd., the well-known chemical manufacturers of Northwich, Cheshire, England, for the new and enlarged edition of the publication, "Silicate Of Soda and Concrete," which gives a clear and concise account of the whole matter. Silicate of soda is manufactured by fusing together a good grade of sand (Silica, Sioy 2 ) with soda ash, and the glasslike product obtained is then generally dissolved in water under special conditions and sold as a colotuless liquid.

When a sufficienty diluted solution of this is applied to .a clean and dry concrete surface the result is the formation of a dense and hard outward layer, which is much mor-e resiistant than .the untreated concrete to abrasion, impact, cutting, scraping and slicing actions, and every other factor that may be included under the general term “wear and tear,” whilst at the same time, as already indicated, the permeability to water is reduced in a very pronounced manner, and the same applies to oil. In the new publication there will be found in the first place a very clear description of the method of applying the treatment, which is quite simple, consisting merely in dissolving one part of the commercial' Bblution in four parts of water, spraying or painting this over the surface, and then allowing it to lie for 24 hours.. The process is carried out three times in succession, and in addition to simplicity has. the merit of cheapness, costing less than %d per square yard for the three coats, whilst the appearance and texture of the concrete is not altered nor is the surface rendered slippery, an important point for roads and floors. Also, the effect lasts at least twelve months, and it is an easy matter to renew the treatment.

It is only fair to state that the great success now being obtained with the process is largely due to the extensive research work Messrs Brunner, Mond and C 0.., Ltd., have devoted to. the whole question ~of the manufacture ■ and application of silicate of soda. As a result it is now clearly established, as already indicated, that for the best results it is necessary to use in a state of sufficient dilution silicate of soda of the correct “ratio,” that is the figure which expresses the number of molecules of silica (SiOi%) combined with one molecule of soda The promiscuous use of any grade of silicate of, soda, such as for example “water glass,” as generally used for egg preserving, .will not give the best results, and there is supplied for the purpose a grade known as P. 84, which has a ratio of 3.3 and is found afs a result of research and experience to be extremely satisfactory. The chemical reactions which are the.cause of the beneficial effect appear somewhat complicated, but essentially the silicate of soda solution "penetrates the pores, present in even the best concrete, to a depth of onequarter to half an inch, and combines with the free hydrated lime present (originally liberated .in the setting of the cement) to give calcium silicates. Also free silica (SiO%) is separated, and in addition tne carbon dioxide of the atmosphere combines with the lime to give, calcium carbonate. The nett result is to fill up completely all the pores with-'an intensely hard silicons mortal' or binding material, and ample evidence as to the practical value of the process is. available from many different users, whilst an actual demonstration was given by Mesprs Brunner Mond as part of! their exhibit in the chemical section in the Palace of Industry at the British Empire Exhibition, Wembley,.with the aid of a motor-driven abrasion machine, showing that concrete blocks sb treated are very much more resistant than ordinary concrete blocks.—Dairyfarmer.