August 2003 Table of Contents

Features California's First RCC Dam

A remote San Diego County canyon has just witnessed an impressive engineering feat—the construction of California's first major roller-compacted concrete (RCC) dam. At 318 feet high and 2500 feet long, it is North America's tallest RCC dam. It is designed to remain operational during and after a Richter 7.2 earthquake. Read more

Features Better Concrete Practices for Residential Construction

As the least regulated and least sophisticated of all segments of the concrete industry, scaling and spalling problems in residential concrete should come as no surprise. Although both the American Concrete Institute (ACI) and the Building Officials and Code Administrators International (BOCA) have specifications and guidelines for residential concrete, they are seldom read or enforced. It’s rare that cities and villages have anything more than a strength requirement for footings, foundations, and flatwork. Read more

Features Express Air Measurement

Concrete specifications for high-durability concrete may soon take on a new look thanks to an air void analyzer (AVA) being demonstrated by the Federal Highway Administration (FHWA). The device, reminiscent of a lava light with a PC interface, was developed more than a decade ago by the European firm Dansk Beton Teknik (DBT). It gives much more data about air entrained in concrete than the standard pressure pot or roll-a-meter, which give only the total percentage of entrained air. Read more

Decorative Concrete Penetrating Sealers for Decorative Concrete

The two types of sealers for concrete are film-forming and penetrating. Film-forming sealers adhere to the surface of concrete, providing a waterproof barrier so long as the application covers all the voids and there are no cracks. Penetrating sealers move through the voids and capillaries at the surface and penetrate into the subsurface of the concrete. Read more

Problem Clinic Maximum Concrete Temperature

Some concrete specifications contain a maximum temperature for the freshly mixed concrete as delivered. Typical values are between 80° and 95° F as measured by ASTM C 1064-86. Over the years, I have seen very little to support the validity of having a max Read more

Problem Clinic Exposed Aggregate Concrete Doesn't Set

I recently poured an exposed aggregate driveway. The concrete came with retarder in the mix and I also sprayed retarder on top. The next morning some spots were still wet at the surface and the rest of the load was completely set. This was a 90-degree day Read more

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