×
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

Concrete Mix for Headworks at WWTP

Concrete Mix for Headworks at WWTP

Concrete Mix for Headworks at WWTP

(OP)
This is for all of you WWTP designers out there. What mix design have you been using for Headworks structures, or other structures with relatively high exposure to sulfates? We have generally been using the same mix design we use for all watertight structures (f'c = 4,500 psi, w/c = 0.42, Type II cement, 6% air) as recommended by ACI350-06 Table 4.3.1 for 'moderate' sulfate exposure, and then recommending the Headworks be lined with a protective coating. But I'm wondering if it might be beneficial to jump to the 'severe' sulfate design mix for the headworks (f'c = 5,000 psi, w/c = 0.40, Type V cement, 6% air) instead. My only concern here is that for some of the small municipalities, Type V cement might be hard to come across. Any thoughts?

RE: Concrete Mix for Headworks at WWTP

Not sure of your application (WWTP?), but we have high sulphate soils and usually use w:c <= 0.4 and regular type 10 cement (here, GUb) with 25% flyash... low slump and strength noted is good. 5% to 7% air for exterior exposure for freeze-thaw...

Lean towards fly-ash with type 10 because of chloride issues. Type 50 (here HS) is contraindicated for chloride resistance.

Dik

RE: Concrete Mix for Headworks at WWTP

We've not had problems with sulfate attack, at least on the inside of our headworks. We use a .4 w/c concrete with type II cement and fly ash content of 15 to 18% (amount of fly ash usually at the disgression of the batch plant). We're in Phoenix and we routinely don't add air entrainment.
I'd be much more worried about hydrogen sulfide attack on the inside head space of the channels. And there's no concrete mix known that's going to be resistant to that. You're either going to need to put a liner on the concrete (T-Lok) or coat with a hydrogen sulfide resistant coating like Plasite or Sauereisen.

RE: Concrete Mix for Headworks at WWTP

WWTP=waste water treatment plant. In my limited experience, sulfate attack hasn't been an issue. Actually I haven't seen anyone use epoxied or galvanized rebar on environmental projects.

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