2 BULLETIN 407^ U. S. DEPARTMENT OF AGEICULTTJRE. 



plain macadam with bituminous surface treatments, and bituminous 

 concrete. Supplementary reports, describing the progress of experi- 

 ments previously reported, follow the reports of the new experiments. 



EXPERIMENTS ON MOUNT VERNON AVENUE ROAD, ALEXANDRIA 

 COUNTY, VIRGINIA. 



BITDMINOUS MACADAM (PENETRATION AND MIXING METHOD), BITUMINOUS GRAVEL 



CONCRETE. 



This experimental project is located in general upon the Mount 

 Vernon Avenue Road, in Alexandria County, Va. The entire project 

 deals with the bituminous type of road construction. It begins at the 

 Military, Road, near the Arlington Cemetery, and extends on a new 

 location to McKinley Street. Passing through McKinley Street to 

 Columbia Pike, the road then follows a new location to the top of the 

 hill near station 37 + 00, where it joins Mount Vernon Avenue. The 

 old location of Mount Vernon Avenue is left again at station 85 +00, 

 and a new location is followed across Four Mile Run to Mount Vernon 

 Avenue at approximately station 131+00. From there the road 

 continues along Mount Vernon Avenue to Washington Avenue, 

 thence through Washington Avenue and Washington Street to the 

 city line of Alexandria. The total length of the project is 23,711 

 feet, or approximately 4.5 miles, and is divided into 20 experiments, 

 as shown in Table 1. The experiments are numbered consecutively 

 from the north end of the project toward Alexandria, and the experi- 

 ments numbered 9 and 12 are identical in the construction methods 

 employed. 



The project naturally falls into three sections, according to the 

 nature of the construction of the road base. Section I extends from 

 the north end of the project (station — 1+61) to station 153+00 at 

 Hume, where the road crosses the tracks of the Washington-Virginia 

 Railroad. A gravel base was laid throughout this entire section, 

 both on the new location and on the old road, which was of earth and 

 badly-worn gravel. Section II extends from station 153+50 to 

 station 192+00. The base on this section is an old bituminous- 

 macadam surface scarified and reshaped. Section III extends from 

 station 192 + 00 to station 235+50, and the base is an old water- 

 bound macadam surface, scarified and reshaped. 



