Super-Plasticizer for high-rise concrete structure
Super-Plasticizer for high-rise concrete structure
(OP)
I am a structural estimator and have priced many higrise concrete structures from 20 stories up to 50+ stories and just run into a debate of Super-P use.
After spent time digging out these old project data, I found out that every project is different in specifying super-p, even the same structural engineer would specify no super-p on this job but specified super-p on shearwall & columns with more than 10,000psi on similar project a few months later.
Do you know if there is specific ACI requirements about the use of Super-P on highrise concrete?
Thanks
After spent time digging out these old project data, I found out that every project is different in specifying super-p, even the same structural engineer would specify no super-p on this job but specified super-p on shearwall & columns with more than 10,000psi on similar project a few months later.
Do you know if there is specific ACI requirements about the use of Super-P on highrise concrete?
Thanks






RE: Super-Plasticizer for high-rise concrete structure
Super P is a constructability aid or a crutch for contractors, depending on who you ask. It can be touchy to use. It doesn't affect the strength or other structural properties of the concrete and that's what ACI is interested in.
RE: Super-Plasticizer for high-rise concrete structure
RE: Super-Plasticizer for high-rise concrete structure
RE: Super-Plasticizer for high-rise concrete structure
1. highrise with 10,000psi or higher strength of concrete in shearwall and/or col (with pearock, set retarder, etc.)
2. if developers have no objection, use pearock and super-p everywhere, which makes concrete pumping easy and smoot, but cost more money
Any thought?
RE: Super-Plasticizer for high-rise concrete structure
RE: Super-Plasticizer for high-rise concrete structure
You will need a low water cement ratio, to do this you decrease the water and increase the cement. But at increased levels of cement the heat of hydration will reach an unacceptable level.
To counteract this you reduce the water cement ratio not by adding additional cement but by using a superplastiser to enable the water content to be reduced.
The other point is about using "pearock". If I assume that this typically refers to a 10mm crushed aggregate then I doubt the effectiveness unless really necessary due to congested rebar. 20mm aggregate has a lower surface area per weight than 10mm aggregate. It then follows that if you can use the 20mm aggregate you need less cement "paste" to coat it, this has benefits for the water cement ratio.
The other issue with high strength concretes - say in the range 70 - 100 N/mm2 - is heat generation and cracking.
RE: Super-Plasticizer for high-rise concrete structure
RE: Super-Plasticizer for high-rise concrete structure
You were questioning why a structural engineer would specify Super P or SCC on some jobs and not on others. -
Here is one possible reason.- It may depend on the contracting method and the type of structure.
I have many associates that will gladly spec more sophisticated concrete materials if it is a project with known contractors, subcontractors and supliers going in. This provies a level of confidence and reliability and more of a "team" approach.
On other jobs, with the "old Boy Scout" method of design, bid, low bidder and heavier/more intense site controls and testing, they may often go with materials that are more suited toward a more varied "cast of characters". Frequently, these types of publically funded projects can get high visability if there is a hint of a real or perceived problem.
Dick
RE: Super-Plasticizer for high-rise concrete structure
One job, completed by our firm six years ago, as I tracked it out, was on design-built basis, had super-p and pearock mix on entire tower 54 stories. I found out that the Owner, A/E and concrete contractor agreed to do that.