DUST PREVENTION AND ROAD PRESERVATION, 1916. 63 
was rebuilt with Topeka asphaltic concrete. The surface on the 
easterly 100 feet was in fair condition, except along the sides and the 
center from station 13+25 to station 13 + 40, where the seal coat 
had worn through and several potholes had formed. 
Experiment No. 6— Oil-asphalt, penetration method. — In the spring 
of 1916 two small potholes about 7 feet north of the center at stations 
13 + 97 and 14 + 13, and two small potholes at the junction of experi- 
ments Nos. 6 and 7 were patched with broken stone and asphaltic 
cement. No other repairs were made on the section during the year. 
The seal coat was worn through in a number of places and potholes 
were developing on the north side at stations 15 + 40 and 15 + 45, 
where the foundation had been poor. From station 13 + 94 to station 
14 + 38 the surface was disintegrated slightly. 
Experiment No. 7 — Refined coal tar, penetration method. — Potholes 
have formed in the surface from station 15 + 57 to station 16 + 95. 
The south edge from station 16 to station 17 was in poor condition. 
The seal coat was becoming very thin. This section was less wavy 
than any of the other sections and, on the whole, was in good condition. 
Experiment No. 8 — Fluxed native asphalt, penetration method. — The 
slight waviness of the surface was a little more pronounced than at 
the previous inspection. The small pothole at station 17 + 60 had 
disappeared but a depression still was noticeable. On the whole 
this section was in very good condition. 
Experiment No. 9 — Oil asphalt, penetration method. — The surface 
was raveled to a depth of about one-half inch or more in a number of 
places scattered throughout the section. At the easterly end the 
surface abutting the wood-block pavement was particularly bad in 
this respect. This probably was due to a slight difference in grade 
elevation for the two surfaces. 
RfiSUMfi OF PREVIOUS REPORTS. 
Oil-cement concrete, oil asphalt, tar, and fluxed native asphalt. 
This experimental road, 25 feet wide, was built in August and 
September, 1911. The work consisted in resurfacing a 2,000-foot 
length of badly worn, water-bound macadam pavement on Hillside 
Avenue. Before the experimental work was begun the old macadam 
surface was scarified and rebuilt to a crown of three-eighths inch per 
foot by addition of material and rolling. On this macadam as foun- 
dation nine experimental surfaces were laid — one oil-cement concrete 
pavement, four bituminous concrete pavements, and four bituminous 
macadam pavements. The aggregates used in all the experiments 
was clean, crushed trap rock, screened according to the following 
grades, 
