concrete curing

[jejoames]

This question was put to me from a colleague who watched a special on the hoover dam that concrete was still fluid in the center of that large monolithic pour. I said didn't believe this was the case because curing would still take place regardless of its location or quantity. Comments?

 

[JedClampett]

You're right. The concrete cures no matter where it is once the cement and water combine. Concrete will cure underwater. As a matter of fact, the pours for Hoover Dam were so large that that the heat created from the curing process had to be removed with a cooling system of pipes.

 

[MotorCity]

jejoames,

Your colleague was partially correct in his statement. While it is true that portions of the dam are still in the curing process, none of the concrete is still in the fluid state. It is still curing, meaning that it has not completely achieved its full design strength.

 

[SlideRuleEra]

jejoames - I agree totally with JedClampett. MotorCity is technically correct also, but it is highly likely that after about 70 years, the concrete has reached - say 99.99% of its ultimate strength.

 

[BigH]

Just an aside - my first university faculty advisor worked on the design of the water intake system (the late Dean Solomon Hollister of Cornell).

 

[jheidt2543]

Another aside - the University of Wisconsin Civil Engineering Department did an extended study of concrete strength gain over time, using standard test cylinders. At the 50 year point, the concrete was still gaining strength. I believe the study is still in progress and comming up on year 75 pretty soon. I'll see if I can find out any more about it and the location of the publications and post it.

This confirms the conventional "field wisdom" of our laborers when they had to jackhammer out old concrete for demolition jobs. The older it was the harder it was.