December 2000 Table of Contents

2000 Pavement Awards

Concrete paving contractors are placing more and more overlays--a repair option once dominated by the asphalt paving industry. Of the record 26 winners and finalists in 12 categories in the 2000 National Awards Program for Excellence in Concrete Pavement, more than one-fourth of the projects involved whitetopping of asphalt or concrete pavements. Sponsored by the American Concrete Pavement Association and Concrete Construction, the awards recognize contractors, engineers, and owners who completed outstanding projects in 1999. Read more

Features Move Over, Round Dowels

Steel dowels, when aligned carefully and debonded from the concrete, help to carry loads across joints in concrete slabs even after the joints have opened too much to prevent load transfer by aggregate interlock. However, traditional round dowels may cause slab cracking by restraining movement along doweled longitudinal joints when workers place large floor slabs in long, alternating strips, with infill strips placed later. When the infill concrete tries to shrink, the dowels prevent slab movement parallel to the longitudinal joint, causing internal stresses. Read more

Features Concrete Streets for Navajo Nation

Late in the fall of 1999, Ft. Defiance, Ariz., became the first town in Navajo Nation to replace potholed asphalt streets with concrete. The project was so successful that several other towns in the reservation are following Ft. Defiance's example. Navajo Nation is the largest Indian reservation in the United States, covering more than 25,000 square miles and encompassing portions of Arizona, New Mexico, and Utah. The Navajo Housing Authority decided to switch from asphalt to concrete after hearing Ft. Defiance residents complain about all the potholes in their existing asphalt roadways. A key reason for NHA's decision was the good performance of concrete pavements installed 13 years earlier in other residential areas on the reservation. Although the pavements had cracked in many places, the wearing surfaces were intact. Read more

Features Concrete Pump Attaches to Loaders

The skid-steer loader is one the workhorses of the concrete construction industry--especially on small jobs. It can maneuver in tight spaces, excavate for slabs on grade, place and fine grade stone subgrade, and haul loads over rough terrain. More recently, it has become a tool carrier for various attachments. One new item in the tool crib is a concrete pump that attaches to the loader and uses its power supply. The attachment is especially useful for concrete placements of less than 100 cubic yards, and it can work from either side of the loader to accommodate site demands. Read more

Features Are You Ready for 2001?

If you are like most contractors, you are probably sprinting to get jobs completed by the end of the year, eager to get expenditures fulfilled and "off the books." But what about next year? Have you set aside time to plan ahead? Unfortunately, many contractors miss out on the opportunity to plan ahead for profitable growth. Here are five steps to help you build a strategic plan for your business. Read more

Features Do Pan Floats Cause Blisters or Delaminations?

Pan floating significantly increases floor flatness and improves finishing productivity, but can it also cause floor imperfections? Read more

Features Troubleshooting: Honeycomb and Voids

Honeycomb forms when mortar fails to fill voids between coarse-aggregate particles. The defect may be purely cosmetic or, depending on the location and extent of honeycombing, may be structural and require repair. Voids form when concrete fails to fill areas in a form, typically those under large blockouts, in very deep placements, or that are heavily reinforced. Voids are almost always structural defects requiring repair. Read more

Decorative Concrete Coloring Concrete Integrally

Integral color--achieved by adding pigments to concrete before placement--is the most common method for coloring concrete. But successfully installing colored concrete requires that you understand and learn how to manage the problems that can arise. The concrete mix design, weather conditions, and efflorescence all can influence color intensity and uniformity. Here are tips for selecting and using integral colors to produce even-colored, consistent finishes. Read more

Problem Clinic Vertical Rebar Placement in Footings

When placing vertical rebar in a residential footing, is it necessary to tie them in place before the concrete pour, or can workers just "stab" them in after the concrete has been placed and struck off? Read more

Problem Clinic Epoxy-Terrazzo Problem

An epoxy-terrazzo coating on a concrete floor we placed is beginning to blister in two locations. The concrete was placed on a 4-inch-thick granular subbase over a 6-mil vapor barrier placed directly on the subgrade. Do you know of anyone who has tried us Read more

Problem Clinic Does Aggregate Size Affect Concrete Shrinkage?

I've heard that pea-gravel concrete shrinks more than concrete made with a larger maximum-size coarse aggregate. Why? Read more

Close X