What is good concrete?

Submit A Comment | View Comments

For years I’ve tried to answer the question, “What is good concrete?” I’ve written articles on the subject (always a learning opportunity for me), and had come to think I understood what it is and what it isn’t—I probably understand more about what it isn’t.

So when we decided to do a small laboratory research project to see how moisture either moved through concrete or was retained by it, I had already worked out in my mind what the outcome would be. The denser low water-cement 0.35 sample (good concrete) would retain enough water to cure properly in the first 28 days and the sample with the 0.55 would permit moisture to pass through it more easily and wouldn’t attain proper strength. But all four of the mixes we tested maintained moisture levels above 80% relative humidity (RH)—the minimum level for hydration to proceed—during the curing period. They were all good concrete from that standpoint.

We also measured carbonation of the surface of each sample, thinking this would be a way to separate good concrete from bad and we did find differences in the thickness of carbonation between samples. But one of the givens about concrete is that it carbonates, so this doesn’t make it good or bad. In fact, carbonation offers some benefits along with its negatives. The surface carbonation of our samples wasn’t enough to say that one mix might perform better over time than another, though I still have my suspicions.

I hope you’ll enjoy reading the article about the study in the September issue of Concrete Construction, I’m sure you’ll have your own opinions to counter ours about what constitutes good concrete.

— Joe

 
 

Comments

Be the first to add a comment to this post.

Comment on this Post

Post your comment below. If you wish, enter a username and password though they are not required. Please read our Content Guidelines before posting.

 

Enter the code shown in the image

Username is optional

 

Enter a password if you want a username

 
 

About the Blogger

Joe Nasvik

thumbnail image

Joe Nasvik has been senior editor for Concrete Construction (CC) magazine since March 2000, where he writes articles about all segments of the concrete industry and specializes in decorative concrete construction. Nasvik is a member of the American Concrete Institute (ACI) and the American Society of Concrete Contractors, on the board of the Decorative Concrete Council, and represents CC in the Concrete Foundation Association. On the ACI national level, Nasvik is a member of the Construction Liaison Committee, the Aesthetics Committee 124, Decorative Concrete 310, and Decorative Concrete Finisher C601-D. He attends meetings of the 302 Floor Construction committee, 343 Bridge Design committee, 130 Sustainability committee, 117 Tolerances committee, and 363 High-Strength concrete committee.

Considered a leading authority on concrete, Nasvik was a professor in the Applied Behavioral Science Department at a small college until 1974 when he started Chicagoland Concrete Specialists (CCS)—a concrete construction company in the Chicago area. As a Bomanite contractor, his company installed all forms of special pavement. As one of the early stamped concrete contractors, he worked out mix designs for freeze/thaw climate use and performed durability tests in lab testing facilities. CCS also constructed high-strength warehouse floors, installed other general concrete flatwork, and specialized in the installation and waterproofing of landscape features and waterfalls using rock textured panels made with glass fiber reinforced concrete and masonry unit formlined concrete wall construction. Nasvik holds a master's degree in Group Dynamics and a master's degree in Social Work.