38 BULLETIN 407, U. S. DEiPARTMENT OF AGRICULTURE. 



This pavement was completed in May, 1915. When inspected in 

 December, 1915, it showed no evidence of failm-e or appreciable 

 wear. The normal amount of traffic to which the road will be sub- 

 jected is not yet developed, and another year will be required to test 

 the wearing quahties of this pavement. 



EXPERIMENTS AT JUPITER, PALM BEACH COUNTY, FLA. 



OIL-ASPHALT-SAND. 



The purpose of this experiment was to demonstrate a simple and 

 inexpensive method of treating the deep sand roads of Florida which 

 are subjected to light traffic. The demonstration section is on West 

 Lateral Road, 1.8 miles north of Jupiter, Fla. The bitumenized 

 portion is 152 feet long and 9 feet wide, skirted on both sides by 

 untreated sand shoulders 5h feet wide. 



The mineral aggregate used was the native sand found in and along 

 the roadway, in which was incorporated asphaltic materials, the prop- 

 erties of which are given in Table 41. The sandbed was prepared 

 for treatment by removing with hand rakes all twigs, sod, and similar 

 undesirable matter from a width 10 feet on each side of the center 

 hne of the road. The sand in this area was then smoothed down to 

 a uniform grade, while the cross section was shaped to a total crown 

 of about 5 inches over the 20-foot width. 



The bituminous material was heated in 1-barrel kettles and was 

 spread by means of hand-pouring pots in a series of applications, 

 according to what is commonly known as the layer method. Four 

 such apphcations were made. Each was covered with a layer of 

 sand after the bituminous material had been partly absorbed. The 

 sand for this purpose was obtained from the shoulders. Each layer 

 of sand was thoroughly rolled with a 3- ton horse roller before the 

 succeeding apphcation of bitumen was made. The quantity of bitu- 

 minous material and the thickness of the sand cushions in the various 

 layers are stated below : 



(1) One-third gallon of bitumen A per square yard, over which 

 was spread one-half inch of sand; (2) two-thirds gallon of bituminous 

 material A per square yard which was covered with 1 inch of sand; (3) 

 two-thirds gallon of bituminous material A per square yard, followed 

 by a layer of 1 inch of sand; (4) one-third gallon of a combination of 

 equal parts of A and B per square yard, to which was appHed enough 

 sand to absorb the bituminous material. 



The resulting cushion of bitumenized sand is approximately 3 

 inches thick. The original plan involved the use of three layers only, 

 but because of the damp condition of the sand on which the first 

 apphcation of oil was made, the hot asphalt foamed freely and the 

 quantity poured was reduced by one-half. It was necessary, there- 

 fore, to add another thin layer to give the desired depth. 



