×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

high strength masonry

high strength masonry

high strength masonry

(OP)
I'm considering using some high strength masonry on a job. My initial calcs suggest an f'm of 4000 psi would be required.

What I can't seem to find is the required net strength of the CMU units to get me there. All the tables I've found only go up to f'm=3000 psi, but I've found plenty of information on the net that says 4000 psi is possible.

Anyone have any ideas?

RE: high strength masonry

ARKeng,

Assuming the design is in accordance with IBC and not UBC, compliance with f'm for new engineered masonry construction is usually verified by one of two methods:

1. Unit strength method IBC Sec 2105.2.2.1, or

2. Prism test method IBC Sec 2105.2.2.2

The f'm max value of 3000 psi for CMUs is when the unit strength method is used for complaince with f'm. IBC Table 2105.2.2.1.2 or MSJC Spec Table 1, page S-10

IMO, you'll have to go with the prism testing method wherein the whole assemblage(blocks, grout and mortar minus the rebar) is tested.



RE: high strength masonry

I would also check with your local cmu manufacturers to see if you can get blocks of the required strength.  I wanted to use f'm=2000 psi on a project once, and this caused a controversy with the local block mfrs because using f'm greater than 1500 psi in my area is almost never done.

RE: high strength masonry

If you actually require this strength of masonry, why not use precast or cip concrete? I've never heard of 4000 psi masonry before.

RE: high strength masonry

(OP)
MotorCity,

Funny you should ask that: This job was originally CIP concrete and working comfortably with 10" walls (at 4500 psi). Contractor has convinced the owner there's time and money to be saved by going to masonry. I've had to go to 12" CMU and the bottom story is 4000 psi.

I suspect (hope) they may change their mind when they see the details.

RE: high strength masonry

ARKeng,

I think you should proceed with your work, with an eye toward demonstrating whether or not, and where any cost savings would be.  From your description, I believe you may find none.  Complex details and hard-to-supply masonry units both should translate to higher than average costs for the masonry option...  You just might find that the concrete is cheaper after all.


Regards,

chichuck

RE: high strength masonry

I had something similar come up where I wanted to use concrete and they had the money saving conversation without me regarding cmu. I would have so much reinforcing and plus those high strength units, that I didn't even go to the effort that you are and just told them no, it wouldn't work and it would be about as much money if I was able to get the cmu wall to work. I am tired of spending all my budget (which is too little to begin with) trying to do something extraordinary to save somebody else 50 cents.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources