October 1998 Table of Contents

Features Engineered Wood for Form Construction

Dwindling supplies of suitable sawn dimension lumber, as well as the roller-coaster movement of lumber prices, have led some form builders to use other framing materials to support formwork. Structural composite lumber (SCL), a precision-manufactured engineered-wood product, is an alternative that offers some of the same properties of wood along with enhanced strength and reliability. Like ordinary wood, the manufactured beams are workable and easy to handle, but they don't warp or twist, and they're 100% reusable. They reportedly cost less than aluminum and more than sawn lumber. However, they offer a greater return on investment, particularly when you consider that typically 20% or more of sawn lumber is discarded due to defects. Read more

Features Forming Chamfers and Rustications

Rustication grooves, chamfers and drip recesses created to direct rain flow off building surfaces all require carefully detailed formers to achieve satisfactory construction quality. Contractors once had to cut all these pieces from wood, but now an array of ready-made products are available to do the job. Precut wood, elastomeric and rigid plastics, foamed plastics, and metal can be purchased in a variety of sizes and shapes. Some of the plastic strips have attached tails to seal the form joints and internal stiffeners to help maintain accurate dimensions. Read more

Features The True Window of Finishability

Petrographers' reports often cite premature finishing as a major cause for blistering and delamination. And numerous publications tell finishers to avoid floating slabs too soon. But what is premature finishing, and how precise are the methods finishers use to judge the proper time for finishing operations to begin? Read more

Features Using Type K Cement in Waste-Containment Structures

When a concrete containment facility is designed and constructed to be leakproof, cracks are an obvious concern -- especially if the structure is to hold low-level radioactive waste. Read more

Features Controlling Crane Rental Costs

From the time a mobile crane leaves the rental yard until it returns, the rental clock is ticking, costing you money. Rental rates for a crane and operator start at around $100 per hour and can exceed $500 per hour for large cranes. To get the most value for your rental dollar, it's important to select the crane carefully, schedule it efficiently and set it up for maximum performance. Read more

Features Protecting Floors From Chemical Attack

Concrete floors are usually so durable that users pay them scant attention. But when exposed to aggressive chemicals, floors can deteriorate rapidly. If left unprotected, damaged floors can interfere with facility operation and create safety hazards for workers. Read more

Features Choosing an Insulating Concrete Form System

An estimated 8,000 homes in the United States and Canada were built last year with insulating concrete forms -- up nearly 50% from the previous year. Homebuyers cite superior comfort, noise reduction, energy savings, and strength and rigidity as the primary reasons they are opting for concrete rather than wood-frame construction -- and are gladly paying a little more for it. Read more

Problem Clinic Avoid Calcium Chloride in Concrete Placed on Metal Decking

Is it permissible to use concrete with 1% to 2% calcium chloride on an elevated slab that's to be placed on galvanized metal decking? The building is in the Midwest and won't be exposed to any moisture other than the humidity in the air. Read more

Problem Clinic Solution for Settled Approach Slabs

Our state department of transportation is experiencing problems with settlement of bridge approach slabs. Despite its efforts to properly compact the soil beneath the slabs, they soon settle, creating a bump. Are there any solutions to this problem? Read more

Problem Clinic Tie Slab to Wall?

We plan to pour a 4-foot-square slab that's surrounded by a perimeter wall on three sides and an existing slab on the fourth. We plan to match the grade of our new slab with that of the existing slab. Strips of material for isolation (expansion) joints ha Read more

Problem Clinic Premature Pickup Traffic

Someone drove a pickup truck over a concrete driveway my crew had just placed 18 hours earlier. Immediately after the truck was driven off the driveway, a crack appeared in the contraction joint the truck had crossed. What is the possible unseen damage to Read more

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