September 1996 Table of Contents

Problem Clinic Circular Cracks around Columns

We built a slab on grade in a building with rectangular concrete columns. We isolated the columns from the slab by wrapping them with a compressible material. Roughly circular floor cracks developed around some of the columns. Can shrinkage cause this kin Read more

Problem Clinic Does Water Content Affect Setting Time?

I know that concrete sets due to a chemical reaction between the cement and water. But does water-cement ratio also affect the setting time? Read more

Problem Clinic Can You Broom Texture a Hard-Troweled Surface?

We're working with a specification that calls for final troweling until the trowel makes a ringing sound as it moves over the surface. This is to be followed by scarifying the surface with a soft-bristled broom. I don't think the broom will scarify a hard Read more

Problem Clinic D-Cracking Versus ASR-Cracking

We've got a series of parallel cracks along the joints in our concrete parking lot. An engineer says they're D-cracks. Is this kind of cracking caused by alkali-silica reaction (ASR)? Read more

Problem Clinic Avoiding Scaling and Sheet Scaling

I'm the construction coordinator for a city in a freeze-thaw region. Deicer scaling and sheet scaling of city streets are both a concern to us because either form of this distress can affect pavement aesthetics and cause surface roughness. Read more

Problem Clinic Effect of Absorbed Water on Water-Cement Ratio

How does water that's absorbed by aggregates affect concrete's water-cement ratio? Read more

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