DUST PREVENTION AND ROAD PRESERVATION, 1915. 



41 



The cost of construoting this section was disproportionately high 

 andean not be fairly compared with that of producing the other sections 

 of the series. Neither is it a just criterion of the cost of building a 

 sand-asphalt pavement. Hence the cost data are not given. 



Table 42. — Mechanical analyses of sands used in experiment No. 8, West Palm Beach, 



Fla. 





No.l. 



No. 2. 



Mixed. 



Retained on 10-mesh sieve 



Per cent. 



0.0 



.3 



4.2 



23.9 



31.2 



36.9 



2.4 



1.0 



.1 



Per cent. 



0.1 



.4 



1.2 



3.5 



5.2 



36.9 



21.5 



29.5 



1.6 



Per cent. 

 0.1 



Retained on 20-mesh sieve 



.2 



Retained on 30-mesh sieve 



2.3 



Retained on 40-mesh sieve 



11.4 



Retained on 50-mesh sieve 



16.4 





36.4 



Retained on lOO-mesh sieve. 



15.4 





17.2 



Passing 200-niesh sieve 



.6 







Total 



100.0 



100.0 



100.0 







COST DATA. 



This pavement was inspected in December, 1915. It had grown 

 slightly wavy under traffic, but had not failed in any other respect. 

 No difference in behavior or surface appearance was noticeable in 

 the three subdivisions of the section. 



EXPERIMENTS AT OCALA, FLA. 



OIL-LIMESTONE, SAND-ASPHALT. 



Among the road materials locally available in Marion County are 

 sand-clay, a fairly well-graded sand, and easily crumbled oolitic 

 limestone, which hardens somewhat on exposure to the air. It is 

 apparently similar in character to but much softer than the coralline 

 rock used in the Miami and West Pahn Beach experiments. In 

 1915 an object-lesson road was constructed of sand-clay near Ocala, 

 and on completion of this it was decided to construct experimental 

 sections adjacent to the sand-clay road, utihzing the hmestone and 

 sand with bituminous materials. The series was installed in the 

 spring of 1915 on the Ocala-Blichton road, about 3^ miles west of 

 Ocala. Limestone for the oil-limestone experiment was obtained 

 from a deposit which outcropped about 1 mile from the road. It 

 was quarried with the use of dynamite and heavy sledges and in this 

 way was easily broken to the desired size. For the surface course 

 of the oil-limestone experiment the limestone was screened at the 

 quarry over a ^-inch screen, yielding approximately 50 per cent 

 retained on a ^-inch screen and passing a 3-inch screen. A suitable 

 quality of sand for the sand-asphalt experiment was located about 

 two-fifths of a mile from the road. 



The equipment consisted of 2 sirup-heating kettles of 200 and 

 80 gallons capacity, which were set in a stone furnace and heated 



