EXPANSION AND CONTRACTION OF CONCRETE. 17 



them from closing when the expansion of the adjacent concrete took 

 place. The section of road read on July 3 was adjacent to a stretch 

 of bituminous concrete laid on a concrete base. On the very hot 

 day preceding these readings there was an upheaval at the junction 

 of the concrete section with the bituminous concrete section, and the 

 concrete base of the bituminous pavement was sheared off to some 

 extent. Note that one of the cracks had opened more than one-eighth 

 of an inch when the readings were taken. 



Measurements made on August 19 are very little different from 

 those of the preceding February, notwithstanding the high tempera- 

 ture existing during the August readings. The September 5 and 

 June 17 readings also are peculiar in that they show very little change 

 from those of the preceding winter, and, moreover, the June 17 read- 

 ings still show .contraction, notwithstanding the hot weather. On 

 June 18, with the temperature not greatly different from that of the 

 preceding clay, a slight expansion was shown. No definite conclu- 

 sions can be drawn from the remaining readings of the third set. 

 Some of the cracks which had opened in the preceding winter re- 

 mained open during the summer, and others became smaller. 



In April, 1914, an incomplete set of readings was taken and the 

 concrete in general showed decided contraction compared with the 

 preceding summer. The contraction of the concrete was accom- 

 panied by an opening of the cracks. The low temperature here seems 

 to have played an important part in influencing the length of the 

 concrete. 



The fifth set of readings, taken in the spring and summer of 1914, 

 on the whole shows the same characteristics as the third set. In the 

 previous July (1913) the section of road which had buckled was cut 

 out and filled with three double courses of vitrified paving brick 

 with tarred joints. In the spring of 1914 buckling again took place 

 at the same spot, and the bricks were removed and the space filled 

 with concrete. 



Note that at the fifth set of readings some of the cracks showed 

 by actual measurement an opening of nearly one-quarter of an inch 

 at the section where maximum expansion took place. The crack 

 openings were even wider than during the preceding summer. Un- 

 fortunately, no measurements were made over this section during 

 the winter of 1914. It is probable, however, that such readings would 

 have shown that the cracks had opened very wide at this season and 

 then were prevented from closing again because of becoming filled 

 with loose material. It will be seen that at other sections of the road 

 cracks which were indicated as quite small by some of the previous 

 readings had opened wide. Note the large expansion in the crack 

 which opened in the plain-cement gravel-aggregate section, read on 



