April 1993 Table of Contents

Features Epoxy Injection of Cracked Slabs

Epoxy injection is a proven technique for bonding cracked concrete sections. A successful epoxy injection requires evaluation, preparation, and planning. Before beginning epoxy injection repairs, identify the cause, or causes, of the problem. Also, be sure that epoxy injection is a proper repair method. Epoxy injection is one element of structural repair, but may only be part of the solution. Read more

Features Good Vibrations

Vibrating screeds not only make a job less labor-intensive, they also let you do it faster and more efficiently. Some manufacturers claim that using a vibrating screed can cut finishing costs up to 50%. Savings like that can allow you to do more jobs at greater profit. Read more

Features Placing Flat Floors

Small and mid-size contractors should be aware of floor flatness concepts and some inexpensive ways to improve flatness. Improved flatness can be a marketing advantage, attracting new and repeat customers and providing opportunities for more work. Read more

Features Forms for Circular Tank Walls

Contractors who build circular tanks can choose from a variety of forms - wood or steel, job-built or manufactured, ganged or handset, custom or off-the-shelf. Some forms are adjustable for a wide range of radius dimensions; others can be used for only a single radius. All the methods, properly applied, can produce structurally satisfactory concrete. Which method to use depends on its cost and ability to meet specification requirements - both of which will be influenced by local labor and site conditions. Read more

Features Measuring Air in Fresh and Hardened Concrete

Current methods can measure only the total air content of fresh concrete, not the gradation of air bubbles. Even so, it's important to measure the total air content in fresh concrete for two practical reasons. First, specifications may require a minimum or maximum air content. Testing shows if the concrete meets specified requirements. Second, a consistent air content indicates uniform materials and batching, and is essential to a consistent yield. Read more

Features Shotcrete Application Tolerances

Because of finishing techniques for shotcrete construction, some tolerances must be larger than those achievable with formed construction. This allowance for increased tolerances need not diminish the serviceability, durability, or integrity of a structure. Tolerances provide an indication of the expected finished product and can identify applications where additional effort and cost may be required, or where a particular construction method may be inappropriate. Therefore, knowledge of tolerances that are consistently achievable is needed by owners and specifiers so that project requirements can be stated clearly. Read more

Features Tunnel Forms Speed Construction of Multistory Residence Hall

Using tunnel forms for the first time, Blake Construction Co. Inc., San Diego, built an 11-story, concrete-frame residence hall in 16 months. The hall, completed in September 1992, is located at San Diego State University. Blake completed the structure on schedule, building a 30-room floor every 6 days, on average. Read more

Features Five Barriers to TQM in Construction

Recently, more and more U.S. businesses have turned to Total Quality Management (TQM) to give them a competitive advantage. Gradually, construction firms also have begun to adopt TQM philosophies. Read more

Problem Clinic Detail Calls for Wire Mesh That's Continuous Through a Keyway

We're building a floor for which the plans call for keyed construction joints. The plans also call for wire mesh that runs continuous through the joint. We don't think this is a good detail either for constructibility or for floor performance. How can we Read more

Problem Clinic Building Post-Tensioned Slabs on Grade

We're going to be placing and finishing the concrete for a post-tensioned concrete slab on grade in a warehouse. It's the first time we've done a post-tensioned floor. How does a post-tensioned floor differ from a conventional floor, and where can we get Read more

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