July 1991 Table of Contents

Features Combating Corrosion in Both New and Existing Parking Garages

There are several ways contractors can build or retrofit concrete parking structures to ward off the effects of chloride-induced corrosion. J. E. Dunn Construction Co., Kansas City, Missouri, demonstrated two of these methods on separate projects: Read more

Features Testing for Chloride Permeability of Concrete

The rapid chloride permeability test (RCPT) determines chloride permeability by measuring the number of coulombs able to pass through a sample. The rapid chloride permeability test consists of two parts:To obtain consistent chloride permeability values for a concrete batch each slice is conditioned to start at the same moisture content. Then the concrete is tested by measuring the charge passed through the slice when one side of the specimen is in contact with a sodium chloride solution and the other side is in contact with a sodium hydroxide solution. Read more

Features Cathodic Protection Also Protects Costs

When Carl Walker Engineers, Kalamazoo, Michigan, was asked to evaluate the spalled parking garage of the Mutual Insurance Co., Providence, Rhode Island, it considered five rehabilitation options. The chosen repair method had to offer a long service life and minimal maintenance. Cathodic protection was decided upon as the best option. Read more

Features Repair and Retrofit Using External Post-Tensioning

Until recently, repair and retrofit options were limited and costly. The usual solution for a sick building is to add steel beams underneath sagging floors and a concrete topping. But while this method may achieve its objective, the cost, disruption to utility services, and unsightly steel work may be unacceptable to building occupants and owners. Rather than face these obstacles, some owners opt to tear down and start from scratch. But now there is an alternative to these methods. External post-tensioning (EPT) has been successfully applied to repair or retrofit about 30 concrete structures in the United States. Read more

Features Protecting Concrete from Exposure to Aggressive Chemicals

Containment areas surrounding chemical process equipment such as tanks, pipes, and valves are often constructed of concrete. This concrete has to be protected from exposure to aggressive chemical environments. Four major factors affect lining or coating product selection: chemical exposure, compatibility with the substrate, application conditions, and type of exposure. Also, the nature of concrete, the frequent requirement for traffic-bearing surfaces, and the aggressiveness of the chemical environment make thick film coatings and linings the best choice. Read more

Bracing for Wall Formwork Features Bracing for Wall Formwork

Bracing for formwork is needed for stability and alignment when storms and strong winds hit. Experience has left some important lessons for contractors working with wall formwork. One lesson is to avoid working in strong winds. Read more

Features Get Tough on Safety Before the Government Gets Tough on You

It is clear that the government is serious about safety. In 1990, 22,578 citations for alleged Hazard Communications Standard (HazCom) violations were issued in the construction industry. The U.S. Bureau of National Affairs, which tracks OSHA activities, listed construction as one of OSHA's prime targets because of the industry's poor record in reducing serious accidents. Another indication of OSHA's interest in construction is the new OSHA Office of Construction and Engineering. Its purpose is to provide technical construction advice to OSHA. Read more

Problem Clinic Condensation Causes Slippery Sidewalk

At a building we built 4 years ago, water appears on the sidewalk near one entrance every morning during the cooler fall months. It usually freezes and is a slipping hazard. The condition is localized and as soon as the temperatures get colder into the wi Read more

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