194 



ANNALS NEW YORK ACADEMY OF SCIENCES 



was four inches, and the concrete used was somewhat leaner. Test No. 4 

 represents the direct qualitative effect of the addition of an excess quan- 

 tity of mixing water without subsequent handling. All specimens were 

 cylinders six inches in diameter and 12 inches high. The remainder of 

 the batch of concrete in each case was poured directly into molds, and the 

 specimens were broken at 28 days. The amount of cement lost was 

 roughly ascertained where possible by filtering the siphoned water and 

 weighing the amount retained on the filter. 



Table 6 



Effect of Excess of Mixing Water on Strength of Concrete 



Test No. 



No. of 

 specimens 



Proportions 



Per cent 

 of water 



Strength at 28 



days, pounds 



per sq. in. 



Per cent of 

 cement lost 



1 

 l 5 



2 



2 5 



3 

 3 5 



4 



4 



3 



2 



3 



2 



3 

 3 



3 

 3 



1:2:4 

 1:2:4 



1:2:4 

 1:2:4 



1 : 2.33 : 5 

 1 : 2.33 : 5 



1:2:4 

 1:2:4 



8.2 

 8.2 



8.2 

 8.2 



8.2 

 8.2 



8.2 

 10.3 



1240 

 760 



1485 

 770 



1490 

 315 



1385 

 1155 ' 



10 

 12 



^Specimens shoveled into water as described. 



Evidently, then, the mere presence of an excess of water is sufficient to 

 produce the weakening effect, independently of any actual removal of 

 cement from the concrete. As may be seen from Nos. 1 to 3, the leaner 

 mixes suffer the greater deterioration in strength. 



Effect of excess of mixing water on permeability of concrete. — A par- 

 allel series of tests upon the permeability of concrete treated with an 

 excess of water was made, in which the correspondingly numbered speci- 

 mens were treated in the same manner. The cylinders cast from these 

 batches were eight inches in diameter and six inches in length, and were 

 cased in the standard manner for permeability tests. Three specimens 

 were made for each test, and at the age of 28 days were submitted first to 

 40 pounds pressure for one hour, then to 80 pounds for one hour, without 

 interruption. The flow recorded is in grams passing during the last ten 

 minutes of test. 



