SAMPLING AND TESTING HIGHWAY MATERIALS. 19 



(13) Cement shall not be rejected on account of failure to meet the fineness require- 

 ment if upon retest after drying at 100° C. for one hour it meets this requirement. 



(14) Cement failing to meet the test for soundness in steam may be accepted if it 

 passes a retest using a new sample at any time within 28 days thereafter. 



(15) Packages varying more than 5 per cent from the specified weight may be 

 rejected; and if the average weight of packages in any shipment as shown by weighing 

 50 packages taken at random is less than that specified, the entire shipment maybe 

 rejected. 



TESTS. 



Sampling. 



(16) Tests may be made on individual or composite samples as may be ordered. 

 Each test sample should weigh at least 8 pounds. 



(17) (a) If sampled in cars one test sample shall be taken from each 50 barrels or 

 fraction thereof. If sampled in bins one sample shall be taken from each 100 barrels. 



(6) If sampled in cars one sample shall be taken from one sack in each 40 sacks 

 (or .1 barrel in each 10 barrels) and combined to form one test sample. If sampled 

 in bins or warehouses one test sample shall represent not more than 200 barrels. 



(18) Cement maybe sampled at the mill by any of the following methods that may 

 be practicable as ordered: 



(a) From the conveyor delivering to the bin at least 8 pounds of cement shall be 

 taken from approximately each 100 barrels passing over the conveyor. 



(b) Proper sampling tubes inserted vertically may be used for sampling cement in 

 filled bins to a maximum depth of 10 feet. Tubes inserted horizontally may be used 

 where the construction of the bin permits. Samples shall be taken from points 

 well distributed over the face of the bin. 



(c) Sufficient cement shall be drawn from the discharge openings in filled bins to 

 obtain samples representative of the cement contained in the bin, as determined by 

 the appearance at the discharge openings of indicators placed on the surface of the 

 cement directly above these openings before drawing of the cement is started. 



(19) Samples preferably shall be shipped and stored in air-tight containers. Sam- 

 ples shall be passed through a sieve having 20 meshes per linear inch in order to 

 thoroughly mix the sample; break up lumps and remove foreign materials. 



Chemical Analysis, 

 loss on ignition. 



(20) One gram of cement shall be heated in a weighed covered platinum crucible, 

 of 20 to 25 c. c. capacity, as follows, using either method (a) or (6) as ordered: 



(a) The crucible shall be placed in a hole in an asbestos board, clamped horizontally 

 so that about three-fifths of the crucible projects below, and blasted at a full red heat 

 for 15 minutes with an inclined flame ; the loss in weight shall be checked by a second 

 blasting for 5 minutes. Care shall be taken to wipe off particles of asbestos that may 

 adhere to the crucible when withdrawn from the hole in the board. Greater neatness 

 and shortening of the time of heating are secured by making a hole to fit the crucible 

 in a circular disk of sheet platinum and placing this disk over a somewhat larger hole 

 in an asbestos board. 



(6) The crucible shall be placed in a muffle at any temperature between 900° and 

 1,000° C. for 15 minutes and the loss in weight shall be checked by a second heating 

 for 5 minutes. 



(21) A permissible variation of 0.25 will be allowed, and all results in excess of the 

 specified limit but within this permissible variation shall be reported as 4 per cent. 



