EXPANSION AND CONTRACTION OF CONCRETE. 21 



on the road for two weeks and was kept wet. At the end of that 

 time it was removed and the road opened. 



LOCATION OF EXPERIMENTAL SECTIONS. 



The three 300-foot experimental sections referred to above were 

 located on the road as follows : 



Section I, in Licking County, one-half mile east of National Road 

 Station. This section comprised the last 300 feet at the bottom of 

 a 4 per cent grade 2,000 feet long. The coarse aggregate was lime- 

 stone, and the section was laid July 6, 1914. The distances between 

 expansion joints varied from 100 to 20 feet, as noted above, with the 

 100-foot section at the bottom of the grade. At the time of laying 

 bronze plugs, similar to "those used in the Chevy Chase experiments, 

 were cast 10 feet apart along the center of the road. Readings on this 

 section were taken on July 7, 8, and 22, on October 31, 1914, on March 

 4 and June 19, 1915, and on February 25, 1916. 



Section II, in Licking County, about 500 feet east of Moscow 

 Bridge, on a 0.4 per cent grade. Limestone was used as the coarse 

 aggregate, and the spacing of the joints and placing of the measuring 

 plugs was the same as on Section I. The first 180 feet of this section 

 was laid on July 29 and the last 120 feet on July 30. This break was 

 caused by an accident to the mixer. Readings were taken on August 

 1, November 2, 1914, on March 3 and June IT, 1915, and on Febru- 

 ary 25, 1916. 



Section III, in Muskingum County, at Mount Sterling. This sec- 

 tion was laid at the bottom of a vertical curve with a 6 per cent grade 

 400 feet long rising eastward and a ,6 per cent grade 600 feet long 

 rising westward. Gravel was used as a coarse aggregate. The sec- 

 tion was laid on November 5, 1914, and readings were taken Novem- 

 ber 6 and 7, 1914, March 6 and June 15, 1915, and February 22, 1916. 



Measurements on Section I. 



The initial readings on Section I were taken on July 7, 1914, one 

 day after the concrete was laid. The temperature of the concrete 

 was determined by means of a thermometer inserted in a small brass 

 tube cast in the top of the pavement, the thermometer bulb being 

 about 4 inches below the surface of the pavement. The hole was 

 packed with putty and covered with a box to protect it from the sun, 

 and here the thermometer was allowed to remain until a uniform 

 temperature was obtained. On July 8, one day after making the 

 initial readings, or two days after the concrete was laid, the second 

 set of readings was taken and is shown graphically on the curve. If 

 a crack is included within the 10-foot gage length, the reading is in- 

 dicated by a dotted line; if a construction joint is included it is 

 shown by a dash and dot line. Almost all the readings taken over 



