Maximum w/c for concrete used for pavement, sidewalk, and curb

[raydefan]

I am a roadway designer and typically write specifications using the Greenbook. I recently had a construction manager reject a concrete pavement submittal because he thought the w/c of 0.57 was too high (even though the concrete compressive strength and slump was met) and recommended that it be under 0.45. The w/c was adequate based on the aggregate grading, slump and table 201-1.3.3(A) of the Greenbook. I typically don't modify the Greenbook unless I know exactly why I am doing it. Does anyone have an opinion on why a lower w/c ratio is benificial?

Thanks,

 

[Ron]

You can achieve compressive strength requirements at almost any w/c ratio....what you compromise for aggressive applications such as pavements is the durability. Keep the w/c ratio below 0.50 for pavements. 0.45 is great, but more difficult.

A lower w/c ratio will result in a more durable mix, capable of withstanding abrasion and abuse that are common for pavements.

 

[raydefan]

Thanks for the response Ron. As a follow up question I now thinking that I should revise the Greenbook to say something like the w/c ratio needs to be less than 0.50 for PCC pavement, driveways, sidewalks, curbs, etc. My only concern is that this will increase the cost of those items. Do you know if it much more expensive? If not, I guess I could just call a concrete company.

Thanks again.

 

[dik]

Way too high... due to salt and freeze-thaw issues in these environs... w/c = 0.4 max is what I swear by... and easy to obtain.

Dik

 

[Ron]

raydefan....of course it will increase the cost...but the benefit is worth it.

 

[dicksewerrat]

I always asked for .4. Then I would harrass the finishers and tell them I wanted .35 with high/early cement and no water added at the jobsite.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[jgailla]

C'mon dicksewer, that's just wrong.

 

[dicksewerrat]

But the concrete is very good. And when I let it go to .43 they are happy.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bridgebuster]

raydefan, if you're in the US use your state DOT specs. NYSDOT has very detailed specs for pavement, sidewalk etc. They use a .44 w/c ratio for pavement.