DUST PREVENTION" AND ROAD PRESERVATION. 7 



The hrick. — Fourteen varieties of paving block were laid, and 

 Table 7 shows their different descriptions and locations. 



Table 7. — Brick used in experiment No. 6. 



Section. 



Location (stations). 



Description. 



From — 



To— 



A 



52+00 



52+51.5 



53 + 19.0 



54+27.7 



55+32.7 



56+44.1 



57 + 13.5 



57+74.0 



58+41.9 



58+91.9 



59+53.2 



60+ 7.9 



60+66.7 



61+26.8 



52+51.5 

 53 + 19.0 

 54+27.7 

 55+32.7 

 56+44.1 

 57+13.5 

 57+74.0 

 58+41.9 

 58+91.9 

 59+53.2 

 60+ 7.9 

 60+66.7 

 61+26.8 

 61+78.1 



Shale (wire-cut lug). 



B 



Do. 



C 



Shale, repressed. 



D 



Do. 



E 



Do. 



F 



Do. 



G 



Do. 



H 



Do. 



I 



Do. 



J 



Fire clay, repressed. 



K 



Do. 



L 



Shale, repressed. 



M 



Fire clay, repressed. 



N 



Fire clay (wire-cut lug). 







The report of tests on samples of these brick is given in Table 8. 



Table 8. — Rattler, sand-blast, and absorption tests on vitrified brick used at Chevy 



Chase, Md. 



Brick. 



Rattler 

 loss. 1 



Sand- 

 blast 

 loss. 1 



Per cent. 



Grams. 



21.12 



27.0 



16.36 



23.3 



25.57 



27.1 



17.67 



32.1 



22.04 



20.6 



18.80 



41.5 



27.92 



35.1 



22.68 



35.8 



22.59 



32.5 



19.11 



37.1 



37.68 



50.5 



38.89 



84.5 



24.31 



44.0 



31.19 



28.5 



Water of 

 absorp- 

 tion — 5 

 brick. 



A.. 



B.. 



C. 



D.. 



E.. 



F.. 



G.. 



H.. 



I... 



J... 



K.. 



L.. 



M. 



N.. 



Shale (wire-cut lug) 2 



do. 3 



Shale, repressed i 



......do.5 



do.s 



do.' 



do.s 



do. 9 



do. 1 " 



Fire clay, repressed u 



dO. 12 



Shale, repressed 13 



Fire clay, repressed u 



Fireclay (wire-cut lug) 16 . 



Per cent. 

 1.39 

 1.31 

 .88 

 1.65 

 1.10 

 1.81 

 2.29 

 3.74 

 2.86 

 1.56 

 2.38 

 4.04 

 3.73 

 3.68 



i Average of three tests. 



2 Hard-burned brick having a good structure. 



3 Medium hard-burned brick having a very good structure. 



4 Brick well vitrified; losses hi rattler mainly due to chipping. 



6 Brick molded from coarsely ground shale; had a fairly good structure and was hard burned. 



6 Brick very hard burned; losses in rattler due to chipping. 



7 Brick molded from coarsely ground clay; had a good structure. 



8 Medium hard-burned brick which wear evenly, though excessively, in the rattler test. 



9 Medium hard-burned brick made from finely ground clay and having a fairly good structure. 



10 Medium hard brick made from coarsely ground clay and wearing down uniformly in rattler. 



11 Brick made from coarsely ground lire clay; had an excellent structure, free from laminations; not 

 burned very hard. 



12 Comparatively soft-burned brick made from coarsely ground fire clay; wear in rattler excessive though 

 uniform. 



13 Comparatively soft-burned brick made from coarsely ground clay; wear in rattler excessive though 

 uniform. 



14 Fairly soft-burned brick made from medium finely ground clay; worn down evenly by rattler. 



15 Losses in rattler due mainly to open laminations; brick hard burned. 



Laying and grouting hrick. — The brick were laid in straight courses 

 at right angles to the curb. No driving was permitted to straighten 

 the courses. After the brick were laid and all the spalls and imper- 

 fect bricks removed, the brick were rolled with a 5-ton tandem roller 



