October 1975 Table of Contents

PROBLEM CLINIC
Problem Clinic Air for Workability in Lightweight Aggregate Concrete

Why should a lightweight aggregate concrete mix for an inside wall in a heated building be air-entrained? Read more

Problem Clinic Removing Reshoring

What is the best rule of thumb on when it is safe to remove reshoring? Read more

Problem Clinic Bundling of Rebars

How many rebars can be bundled, and what must be done about splicing within the bundle? Read more

Problem Clinic Pumping High Density Concrete

Is it possible to place high density concrete by pumping? If so, are there any special methods or precautions needed? Read more

Problem Clinic Fire Endurance of Prestressed Beams

What is to prevent the prestressing steel in a beam from losing its prestress during a fire ant causing an early, quick collapse? Read more

Problem Clinic Expansive Cement and Shrinkage-Compensating Cement

What is the difference between shrinkage-compensating cement and expansive cement? Read more

Problem Clinic Curing Within An Enclosure Using Steam

We plan to place concrete during the coming winter and are wondering about steam curing. is there danger of cracking the concrete if we build an enclosure around the beams and introduce live steam? Read more

Problem Clinic Causes of Changes in Air Content

On a recent job we had excessive fluctuations in air content. The mix contained 490 pounds of cement per cubic yard and was made with 1-inch maximum size aggregate. The air was required to be between 3.5 and 6.5 percent, but sometimes it was considerably Read more

Problem Clinic Don't Remix An Old Mix With a New One

Could a mix of concrete that is too old (2 hours or older) be mixed with a fresh load of the same mix design? Read more

Problem Clinic Protect Against Unintentional Deicer Application

We have a sidewalk that has been through one winter. It was built in August. The top has peeled off to a depth of about 1/8 inch in spots, some about the size of a 25-centpiece and some as big as 2 feet square. Our city uses a thrower to salt the streets. Read more

Problem Clinic Thermal Coefficients of Concretes

We've been told that the coefficient of thermal expansion of concrete is about 5.5 millionths per degree F but that it can be higher or lower. There wasn't any explanation of what changes it. What's the story? Read more

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