32 BULLETIN 401^ U. S. DEPARTMENT OF AGEICULTUKE. 



Table 32. — Unit and total costs. 



Items. 



Unit 

 cost. 



Total 

 cost. 



Clearing and grubbiag, lump sum 



Excavation, 793 cubic yards 



Subdrains, 3,646 feet 4-irich tile 



Scarifying, 5,316 square yards 



Shaping shoulders and subgrade, 4,064 square yards 



Foundation stone, 146,775 tons in place, . . , 



Wearing course, penetration method, 6,421 square yards. 

 Wearing course, sand-oU grout, 367 square yards 



$0. 4704 

 .2145 

 .0304 

 .0371 

 2.196 

 .3284 

 .3942 



$79. 61 

 373. 03 

 782. 07 

 161. 61 

 150. 87 

 322. 32 

 2, 108. 66 

 144. 66 



Total. 



4, 122. 8& 



Sand-Oil Grout (Penetration Method). 



Location: Station 19+00 to station 21+00. 

 Area: 366.7 square yards. 



This section includes two experiments m tlie use of oil asphalt 

 mixed with sand for constructing a bituminous macadam surface 

 according to the penetration method. The first experiment extends 

 from station 19 + 00 to station 19 + 55, and was constructed in a 

 manner exactly similar to that described above for the straight pene- 

 tration work, except that 50 per cent by volume of sand was used 

 with the bitinninous material. The second experiment extends 

 from station 19 + 55 to station 21+00 and was constructed in a 

 similar manner to the preceding, except that only 33 per cent by 

 volume of sand was used with the bituminous material. 



A total of 672 gallons of oil asphalt were used in the two experi- 

 ments, which is at the rate of about 1.83 gallons per square yard. 

 It appears, therefore, that the saving in bituminous material which 

 was effected by employing this method is only about 0.2 gallon per 

 square yard; and if the cost of heating the sand and mixing the 

 oil-sand grout is considered, the cost was greater with this method 

 than with the ordinary penetration method by about 2 cents per 

 square yard. It is very questionable, therefore, if the experiment 

 will prove of value. It wiU be kept under close observation, however, 

 with a view to ascertainiag any possible superiority which this section 

 may possess over the ordinary penetration sections. 



EXPERIMENTS AT WASfflNGTON. D. C. 



BITUMINOUS CONCRETE. 



The bituminous concrete experiments at Washington, D. C, con- 

 sisted in the construction of two wing drives leading from the sheet- 

 asphalt pavement in front of the main building of the United States 

 Department of Agriculture to the sheet-asphalt plaza in the rear, and 

 was completed on December 7, 1915. Each of the drives is approxi- 

 mately 140 feet long and 18 feet wide. The type of construction was 

 bituminous concrete upon a 6-inch foundation of Portland cement 



