April 1984 Table of Contents

Features Charts Simplify Design of Vertical Formwork

Formwork can be simple and straightforward when the designer recognizes the fundamental structural requirements of each member making up the forming system. Each part of the formwork must be within the allowable limits for bending, shear, and deflection. Once these requirements are met, a structurally sound forming system can be built. Read more

Features Formwork for Tooled Concrete

The term tooling refers to several kinds of mechanical fracturing used to achieve a particular visual effect by removing part of the concrete surface. Methods of tooling include abrasive blasting, bushhammering, use of scaling hammers or point tools, and grinding and polishing. The process of producing tooled surfaces commences weeks or even months before the casting operation. Read more

Features Forming Machines Precast Miles of Guideway Girders

Rapid, economical production of more than a thousand prestressed and post-tensioned box girders was crucial to the building of a public transportation system in Vancouver for the 1986 World's Fair. Read more

Features Choosing a Form Release Agent

The basic task of a form release agent is to permit clean release of the form from hardened concrete during stripping. Several types of form release agents are available, some better suited to a particular form material than others. Five basic types are described in this article: petroleum oils; emulsions; non-reactive coatings with volatile solvent; waxes; and chemically active agents containing fatty acids. Read more

Features Forms Fly with Wings Folded

Olympia Centre, a multimillion dollar residential and commercial building in Chicago, presented many unique forming challenges. With a 63-story building on his hands, the forming subcontractor naturally wanted to avoid handset forms and take advantage of the efficiency attainable with big form table assemblies that could be moved out of the building and lifted by crane to the next level, all in one piece. Read more

Features Lightning and Concrete: An Explosive Pair

What do you get when lightning strikes a corn-filled, concrete silo? What a Cresco, Iowa, farmer got after his silo was struck by lightning was a silo full of spoiled corn. The spoilage was actually caused by air penetrating the silo, through cracks in the concrete caused, the farmer believed, by a lightning strike. That's where Iowa State University civil engineering professors came in. Read more

Problem Clinic Transfer Load Between New Slab and Old

We must replace some large areas of highway pavements that contain large, irregular cracks that open and close, some of which intersect. If we remove the old concrete how can we be sure the new concrete won't settle independently or tilt to form faulted j Read more

Problem Clinic Protecting Against Acid Rain

What kind of concrete mix would be most resistant to acid rain, which has become a problem in the New England area? Read more

Problem Clinic Protecting Lead in Concrete

Is there any experience with lead embedded in concrete? A lead-sheathed cable is intended to pass through a 10-foot length of concrete slab-on-grade. Will this cause any problems with the concrete? Read more

Problem Clinic Waste the First Pumped Concrete

In several locations on the walls of an office building we have lighter colored concrete than elsewhere. We've determined that it has always been at locations where we began the day's work. The concrete was placed by pump. Did that have anything to do wit Read more

Problem Clinic Algae in the Mix Water

There is no clear-running stream or other good source of mixing water near one of the sites planned for our portable batch plant, though there is a small lake which is more like a big pond. The trouble is that it contains a lot of green stuff that is repo Read more

Problem Clinic Carborundum for Slip Resistance

I need some information about the application of carborundum chips to walks or driveways and the type of company that sells this product. I have a customer who wants this done on a new home he is building. Read more

Problem Clinic Removing Roofing Tar

A considerable area of our parking lot has been messed up with roofing tar--some of it windblown from the roofing operations and some of it dribbled from buckets and kettles. Cleaning with dry ice and scraper would probably be slow and tedious. Is there a Read more

Problem Clinic Thin Slab on Grade Inadequate for Loaded Trailer Trucks

I have a project erecting a metal building on a good-quality 10-year-old 4-inch slab. I foresee no problem with the wear resistance of the slab, but my client wants to use the facility for servicing his tractors and semitrailers, sometimes fully loaded. D Read more

Problem Clinic From the Concrete or the Blast?

Our laboratory is investigating the cause of an explosion. Read more

Problem Clinic Quiet Breakup

I recall seeing an article in Concrete Construction about some kind of grout material you can pour into drilled holes in concrete and cause the concrete to crack apart so it can be easily broken up and taken away. Read more

Problem Clinic Shallow Waves in Suspended Floor

This sketch shows a ripple problem with a floor finish on a large job we have just completed (8 stories totaling 200,000 square feet of floor). Read more

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