DUST PREVENTION AND ROAD PRESERVATION, 1914. 27 



the west half of the section, and there are a number of small worn 

 areas in the east half. 



(D) Fluxed native asphalt No. 2 over water-gas tar preparation 

 No. 1. — The surface treatment is almost intact on the north half of 

 this section, and the bitumen is still pliable. Over the south half, 

 which includes the intersection with Thornapple Street, the surface 

 treatment is in general worn off. 



(E) Fluxed native asphalt over native asphalt emulsion. — The surface 

 treatment is about two-thirds worn off this section, and the mat 

 appears to be rather brittle. 



(F) Oil asphalt No. 1 over water-gas tar preparation No. 1. — The 

 surface treatment is almost entirely gone from this section. 



(G) Refined coal tar. — The surface treatment is worn off to a great 

 extent over the entire section. 



(H) Water-gas tar preparation No. 2. — The surface treatment is 

 still largely intact, although there are quite a number of small areas 

 ranging in size from one-half square foot to 1 square foot where it is 

 worn off. The majority of these are west of the center line of the 

 roadway. 



(I) Fluxed native asplialt No. 2. — On the east half of the roadway 

 the surface treatment remains in fairly good condition, but the 

 bitumen has become hard, and the surface treatment has disappeared 

 from more than half of the area west of the center line of the roadway. 



(J) Oil asphalt No. 2. — On the west third of this section, adjacent 

 to the gutter, the surface treatment is about one-fourth gone, while 

 over the remainder it is practically intact, excepting for one worn 

 place about 1 square foot in area. Apparently the bitumen still 

 possesses life. 



Experiment No. 4 (Oil-Cement Concrete) and Experiment No. 5 (Cement 



Concrete). 



Xo particular difference was noted in the relative wear on the two 

 classes of concrete. It is, however, interesting to note the difference 

 in wear on the section constructed with trap rock on the grade adja- 

 cent to the vitrified brick experiment. The west half of the road, 

 which e;trries the heavy traffic coming up the hill, is worn to an 

 appreciably greater extent than the east half. The mortar appears 

 to have abraded from around the particles of rock, thus yielding a 

 much roughened surface. Over the remainder of the concrete ex- 

 periment, extending south from the brow of the hill, the wear has 

 been quite uniform over the entire surface. The table following 

 shows tli'' distance between cracks when measured on March io, 1915. 



