SPECIFICATIONS FOR NONBITUMINOUS L'OAD MATEEIALS. 13 



SPECIFICATION RC-1. 



Broken Stone and Sand for One-course Portland Cement Concrete 

 Pavement. 



BROKEN STONE FOR COARSE AGGREGATE. 



The broken stone shall consist of fragments of clean durable crushed General. 



rock, free from soft, thin, elongated or laminated pieces, disintegrated 



stone, vegetable, or other deleterious matter. 



The stone shall meet the following requirements : Physical 



French coefficient of wear not less than 8 I'roP«'"W«s- 



Toughness, not less than 8 



When tested by means of laboratory screens the broken stone for coarse Grading. 



aggregate shall meet the following requirements : 



Per cent. 



Passing 2-lnch screen, not less than 95 



Total passing 1-inch screen 40 to 75 



Retained on J-inch screen, not less than 85 



SAND FOR FINE AGGREGATE. 



The sand shall consist of clean, hard, durable, uncoated stone particles. General. 

 preferably siliceous, free from lumps of clay, soft or flakey particles, loam, 

 and all organic matter. 



It shall be well graded from coarse to fine, and when tested by means Grading. 

 of laboratory screens and sieves shall meet the following requirements : 



Per cent. 



Passing J-inch screen 100 



Total passing 20-mesh sieve 50 to 80 



Total passing 50-mesh sieve, not more than 20 



Passing 100-mesh sieve, not more than 5 



Not more than 3 per cent by weight shall be removed by the elutriation 

 test. 



When the sand is mixed with Portland cement in the proportion of 1 ^•'^t^'^ Strength 

 part of cement to 3 parts of sand, by weight, according to standard meth- ®* ' 

 ods of making 1 :3 mortar briquets, the resulting mortar at the age of 7 

 and 28 days shall have a tensile strength of at least 100 per cent of that 

 developed in the same time by mortar of the same proportions and con- 

 sistency, made of the same cement and Ottawa sand. 



Preliminary acceptance samples shall be subjected to both 7 and 28 day 

 tests, and acceptance based thereupon. Samples tested during the progress 

 of the work will be accepted on the basis of the 7-day test. 



Tests of the physical properties of the rock, the grading or mechanical Methods of 

 analysis of broken stone and sand, and of the mortar tensile strength of Testing, 

 sand shall be made in accordance with the following methods : 



1. Toughness : TJ. S. Department of Agriculture Bulletin 347, page 15. 



2. Grading of Broken Stone : U. S. Department of Agriculture Bulletin 



555, page 32. 



3. Mechanical Analysis of Sand : U. S. Department of Agriculture Bul- 



letin 555, page 33. 



4. Elutriation Test for Sand : U. S. Department of Agriculture Bulletin 



555, page 32. 



5. Mortar Tensile Strength Test for Sand : A. S. T. M. Standard Test 



C9-17. 



This specification provides for coarse and fine aggregate to be 

 used in tlie construction of a one-course Portland cement concrete 

 pavement. While a coefiicient of hardness of not less than 16 for 

 the stone for coarse aggregate might well be included under physi- 

 cal properties, a requirement for French coefficient of wear has 

 been used instead, owing to the fact that few laboratories are 

 equipped with a Dorry hardness machine. 



The 15 per cent of coarse aggregate passing the i-inch screen, 

 which is allowed, is permissible only upon the assumption that 



