Maximum Water-Reducer Ratio's for Mass Concrete Pour 1

[RangeRock]

Good Morning All,

Looking for some experiential wisdom specifying concrete mix proportions for a mass concrete job. We have a medical-grade facility and are designing a concrete "vault" sitting on a mat footing with 9' thick walls in some areas to limit radiation to the rest of the building.

A previous project similar to ours by another engineer had complaints from the owner that the concrete was "sweating" and creating latent humidity due to the massive heat of hydration during hardening. This is obviously not ideal for the highly sensitive equipment within the vault.

We have schematically included doweled construction-joints to limit the massive volume of adjacent pours but are curious what the maximum ratio of water-cement reducer are or applicable code to limit the latent hydration to give the owner a dry & smooth finish surface on the vault walls that does not crack and sweat months after final pours are complete. Thanks in advance!

V/r,

RangeRock484

 

[dik]

9'... mix with chopped ice.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[STrctPono]

RangeRock 484 EIT.

A few thoughts.

Get ahold of ACI 207.2R and read it.
Download ConcreteWorks from TXDOT and run a trial mix to make sure that you don't have a problem.
Control the amount of cementitious material in the mix.
You are correct, incorporation of SCM's will help.
Your concern should not only be differential temperature but max temperature as well that could lead to delayed ettringite formation.
If you feel comfortable that it is achievable but that there is still a concern if not handled by someone competent then you should include a mass concrete spec with your project.
Mass concrete spec should require the contractor to provide a thermal control plan when they submit the mix design. In all honesty, the ready mix supplier, not the EOR is the expert when it comes to concrete and will have a much better idea of how to control the temperature of the concrete.
You may have a hard time specifying this directly, but in your Mass Concrete spec it should tell the Contractor that they may consider iced water, or liquid nitrogen dosing systems. This really depends on how the ready mix company is set up, however.
When all else fails, construction joints (as you alluded to) are the other option.

 

[RangeRock]

Thanks for the responses everyone,

I will give ACI 207.2R a look-see for additional info.

I also agree the conc.-sub should be a SME in this type of construction and that we can specify differential temp. parameters/limits and leave them to achieve those parameters in the most practicable way that meets the mix-design criteria. Will definitely keep a look-out for a thermal control plan during the submittal phase.

Thanks again.

V/r,

RangeRock_484_EIT