October 1997 Table of Contents

Features Using Pan Floats

Using float pans, which are attached to the blades of walk-behind or nonoverlapping ride-on power trowels, offers finishers several advantages, including increased productivity, flatter floors, easier transition from wet to dry areas when floating and superior ability to break open the concrete surface. To obtain the benefits from these advantages, however, finishers must learn how to use the pans properly. Read more

Features Checklist for Selecting a Power Trowel

Article discusses what factors contractors should consider before buying a walk-behind or ride-on power trowel, including design features, productivity, power options, drive mechanisms and ease of control. Read more

Features Vibrating Screed Showcase

Article describes various models of engine-powered vibrating screeds designed to save finishers time, labor and back strain. According to one screed manufacturer, an experienced finisher--with an experienced laborer spreading the concrete--can strike off 20,000 square feet in an eight-hour day when using a vibrating screed. Two men hand screeding with a 2x4--with two men spreading the concrete--would need 10 hours to finish the same area. Read more

Features Concrete Floor Systems in Residential Construction

Used widely in commercial construction for years, concrete floor systems have recently blazed trails into the residential market. The main reason is the growing popularity of stay-in-place insulating concrete form homes. A concrete floor works well with ICFs because concrete walls can carry the floor's greater weight without special provisions. Read more

Features High-Performance Concrete for Wear-Resistant Floors

When high-performance concrete for industrial floors is specified, the concrete must not only perform well in its hardened state, it also must possess certain plastic properties so contractors can properly place and finish it. Read more

Features The Case for a Test Placement

The author, president of a consulting firm that assists in the planning and construction of concrete floors, says that the two most common approaches for judging a floor's surface appearance comparing the final product to a small test panel or evaluating how closely it complies with the project specifications are ineffective. Using small test panels can lead to inaccurate conclusions because the panels often vary from the final product in terms of the amount and uniformity of the concrete used, placing and finishing techniques, and jobsite conditions. Using specifications to judge a floor's appearance can be misleading because the terms used to describe the desired quality are subjective and prescriptive. Read more

Problem Clinic Poor Finish on Parking Structure Slabs

I was called in to advise on problems with a parking structure. The owner is unhappy with the finishing work on all four slab levels. Read more

Problem Clinic Cause of Foundation Cracking

On a hot day in August, we poured 40 lineal feet of concrete foundation wall for a house addition. Read more

Problem Clinic Algae in Concrete Mixing Water

We've got a concrete paving contract in a mountainous region where the only water source is a lake with some algae growth. We've read that water containing algae is unsuitable for making concrete, because the algae reduces strength by interfering with cem Read more

Problem Clinic Rock-Salt Concrete Finish

A client of our New Jersey architectural firm wants to use a rock-salt texture for the concrete deck of her swimming pool. We're not familiar with this process and wondered how the effect is achieved. Read more

Problem Clinic Sources for Rebar Impalement-Protection Devices

Safety inspectors told us that the Occupational Safety and Health Administration now prohibits the use of plastic mushroom caps for protecting workers from impalement on projecting rebar.s? Read more

Problem Clinic Is a 0.44 Water-Cement Ratio Needed For Foundations?

Three different strengths of concrete were specified for one of our jobs in the Midwest: 3000 psi for foundations, 4000 psi for flatwork and 5000 psi for structural members above grade. Specifications give the same maximum water-cement ratio for all three Read more

Problem Clinic Crane Rigging for Tilt-up

What precautions are needed regarding the crane and its rigging? Read more

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