A Treatise On The Principles And Practice Of Harbour Engineering

STONE: NATURAL AND ARTIFICIAL. 105 which the test briquettes are submerged being renewed every seven days and the temperature thereof maintained between 58 and 64 degrees Fahrenheit. “ Briquettes of neat cement of the shape and dimensions shown in fig. 88, having a minimum section of 1 inch square, shall be gauged for breaking at 7 and 28 days respectively, six briquettes for each period. The average tensile strength of the six briquettes shall be taken as the accepted tensile strength for each period. For breaking, the briquettes shall be held in strong, metal jaws of the shape shown in fig. 89, the briquettes being slightly greased where gripped by the jaws. The load must then be steadily PLAN. Fig. 89. —Standard Jaws for Briquette. and uniformly applied, starting from zero and inereasing at the rate of 100 Ibs. in twelve seconds. The briquettes shall bear, on the average, not less than the following tensile stresses before breaking :— 7 days from gauging, 400 Ibs. 28 „ „ 500 ,, The increase from 7 to 28 days shall not be less than : — 25 per cent, when the 7 days’ test falls between 400 to 450 Ibs. 20 ,, ,, „ „ 450 to 500 „ 15 „ „ „ „ 500 to 550 „ 10 „ „ „ „ 550 to 600 „ 5 „ ,, ,, is 600 Ibs. or upwards.