WASHING AND GRADING SAND FOR CONCRETE. I, 
WASHING and GRADING SAND ror CONCRETH. 
By W. EH. Cook, M.C.E., M. Inst. C.E. 
[Read before the Engineering Section of the Royal Society of N. 8. Wales, 
June 20, 1906. } 
In specifications for concrete the various proportions by 
measure are generally given, the second item being clean 
sharp sand, and sometimes the word “ coarse” is used also. 
The object is to produce a mortar sufficient in quantity to 
fill the voids and leave some excess. Olean sharp sand, 
whether coarse or fine, may not be the best material for 
forming a solid mass, or for giving the greatest tensile and 
crushing strength, and the author has collected some infor- 
mation on the subject to place before the Hngineering 
Section. 
In 1900 Professor Sherman, of Ohio University, was 
building a viaduct in Yellowstone Park, when it was 
found that clean sand and water for washing were not 
readily available. After some tests it was decided to use, 
without washing, asand containing from 3 to 7% by volume 
of alkaline earth, organic matter, etc. Upon completion 
of the work some briquettes, made of cement and this 
unwashed sand, showed a higher tensile strength than 
briquettes made of same material after washing. 
To test the matter further a series of tests, extending 
over 12 months, was made. Two kinds of cement were 
used and three kinds of sand, with mixtures of clay and 
loam, viz., 0, 2, 4,6, 8, 10 and 15% by volume of total sand. 
The proportion was 1 part of cement to 3 parts of mixture 
of sand and clay, or loam. The three kinds of sand used 
were crushed quartz (reduced to standard), lake sand 
washed, and bank sand. The clay was first dried and 
ground in a ball mill. The loam was common soil obtained 
1—June 20, 1906. 
