TENTATIVE TESTS. 



39. PROPOSED SOUNDNESS TEST FOR COARSE AGGREGATE. 



Immerse 10 small pieces of the rock in a saturated solution of sodium sulphate 

 (Na 2 S0 4 ), for 20 hours, after which place for four hours in a drying oven maintained at 

 100° C. Repeat the treatment five times. The condition of the rock as to soundness 

 is noted at the end of the test. 



Samples which exhibit marked checking, cracking or disintegration shall be con- 

 sidered to have failed in this test. 



40. TENTATIVE TEST FOR ABSORPTION OF CONCRETE. 



It is recommended that the method of making the absorption test prescribed for 

 cement drain tile in the Standard Specification for Drain Tile, American Society for 

 Testing Materials, Serial Designation C 4-16, be employed for making the absorption 

 test of concrete until a different method is developed. 



41. PROPOSED TEST FOR PERCENTAGE OF SHALE IN GRAVEL. 



It is suggested that for the separation of shale and other pieces having low specific 

 gravity from concrete aggregates, a solution of zinc chloride (ZnCl 2 ) or some other 

 satisfactory liquid having a specific gravity of approximately 1.95 be used. A sample 

 of the pebbles should be first dried to constant weight at not over 110° C, then placed 

 in a container partially filled with the solution. Agitate for five minutes, skim off 

 the lighter materials and then pour the solution through a sieve which will retain the 

 pebbles. Repeat the operation until the entire sample has been separated. Dry to 

 constant weight, measure the volume of retained material and compute the percent- 

 age by volume of shale or other soft material. 



42. PROPOSED MODIFICATION OF THE ABRASION TEST FOR BROKEN 



STONE AND SLAG. 



It is recommended that in order to secure data for a revision of the standard abrasion 

 test for stone, abrasion tests on broken stone and slag be run parallel with the regular 

 test (described on page 3) but with a charge of stone made up in the manner pre- 

 scribed for the charge of gravel for the abrasion test. The purpose is to determine 

 whether it is possible to secure consistent results with a charge for the abrasion test 

 made up from the product of the crusher as it is delivered to the job. 



43. PROPOSED ABRASION TEST FOR FINE AGGREGATE. 



The following is a tentative method for determining the resistance of the fine aggre- 

 gate to abrasion. The fine aggregate is washed and dried at a temperature not 

 exceeding 110° C. All material retained on the 1-inch sieve, and all material passing 

 a standard 50-mesh sieve is discarded. Five hundred grams of the portion passing a 

 }-inch screen and retained on a 50-mesh sieve are placed in a Deval abrasion cyl- 

 inder with a charge of 250 grams of ^-inch commercial steel bearing balls which shall 

 weigh within 1 per cent of the required 250 grams. The charge in the Deval abrasion 

 cylinder is rotated for 2,000 revolutions at the rate of 33 revolutions per minute. The 

 sample of sand is removed and sieved over a 100-mesh sieve. The sample is prefer- 

 62 



