Cement Notes

Progress, Volume IX, Issue 12, 1 August 1914, Page 1205

Cement Notes

By PETER ELLIS

EXCESSIVE RE-INFORCEMENT OF CONCRETE

The cohesion of the constituent particles of concrete is one of its most valuable features; it is therefore very unwise to insert too much iron or steel in the body of the concrete because it cuts up the mass into small portions, thereby lessening its cohesion and destroying its compressive strength. Just enough and no more should be the rule for reinforcement, were it not that concrete lacks tensile strength it would be better probably without reinforcement altogether. Heavy thick reinforcement members should also be avoided, four |in. bars are often better than one |in. and these should only be inserted where the material is subject totension, woven wire of fine mesh should never be used and as a rule round rods and thick plain wire is better than mesh work or punched plating, and

suchlike round rods give the maximum sectional area of metal with the minimum of interference with the cohesive strength of the concrete. IMPERVIOUS WASHES FOR CONCRETE, BRICK, AND STONE WALLS Three-quarters of a pound of Castile soap to one gallon of water laid on boiling hot with flat brush (avoid frothing). Then apply half a pound of alum to four gallons of water perfectly dissolved. WHITE LIME-WASH Slack fresh quick-lime, use enough water to cover it, immediately add boiled linseed oil one pint to a gallon of wash or use common refuse fat for coarser work; Russian tallow is frequently used. STONE COLOUR LIME-WASH Half a bushel (.64 cub. ft.) white lime, one bushel (1.28 cub. ft.) hydraulic cement; slake the lime, add the cement, stir well, add 31bs. sulphate of zinc, previously dissolved in water. The whole should be of the consistency of paint. MONOLITHIC FLOOR SURFACES One of Portland cement, one of clean sharp coarse sand, one of Jin. hard stone passed through Jin. sieve. Novel Bracing for Concrete Wall When a concrete retaining wall, 34ft. high, was to built in San Diego, California, the problem

of bracing it strongly without interfering with traffic was solved by an ingenious scheme. The braces are made of 2in. by Gin. clear Oregon pine,

which are sunk in the ground at the street level and fastened at the top to planks, one end of which is secured to stakes driven in the ground above the cut. Ordinary bracing could not be considered in this case, owing to the narrow space allotted. The wall when completed will be 700 ft. long.