May 1991 Table of Contents

Features The Eastern Scheldt Storm Surge Barrier

The Netherlands and the North Sea have long struggled over territorial rights. After flood waters ravaged the country around the Zuiderzee, several attempts at controlling the waters were made. The Delta Project was an ambitious 3.2-billion dollar barrier across the Eastern Scheldt estuaries. The first three estuaries are spanned by solid dams and dikes. The fourth estuary, however, is spanned by a structure called a storm surge barrier. It links the banks of the estuary with massive gates mounted between huge prestressed concrete piers. It is designed to remain open unless a surge of tidal or storm-driven water is anticipated. The design allows seawater to cycle normally within the estuary, maintaining the saltwater ecology and providing security for the lowlands. Read more

Features Controlled Low-Strength Material

Controlled low-strength material (CLSM) is a backfill product that flows as easily as thick pancake batter and is self-leveling. Its consistency is like that of a slurry or lean grout, yet several hours after placement the material is hard enough to support traffic loads without settling. Typical 28-day compressive strengths range from 50 to 200 psi. Because CLSM flows and needs no compacting, it is ideal for use in tight or restricted-access areas where placing and compacting soil or granular fill is difficult or impossible. Although CLSM costs more per cubic yard than most soil or granular backfill materials, its many advantages result in lower in-place costs. Read more

Features Plastic Aggregate

It is now possible to produce architectural concrete containing aggregate of any color. Researchers have been working to develop plastic aggregates that can replace conventional mineral aggregates in concrete. They have discovered that an engineering thermoplastic called polybutylene terephthalate (PBT) had the greatest potential. Its high mechanical strength, low moisture absorption, and good dimensional stability contribute to its excellent performance as an aggregate. In laboratory test, concrete containing an aggregate mix of virgin and recycled PBT had a 28-day compressive strength of 5500 psi. Because plastic aggregate absorbs little moisture, the concrete also performed well in freeze-thaw durability tests. Also, almost any color shade is possible. Read more

Features 12-Tank Concrete Water Treatment Plant Answers St. Louis Water Purification Needs

The Bissell Point Waste Water Treatment Plant, St. Loius, completed in the fall of 1990, is helping the city's sewer district meet strict EPA water purification requirements. The new plant has three sludge pump buildings, each surrounded by four cast-in-place concrete clarifier tanks. General contractors McCarthy Bros. Construction Co. had to complete the pump buildings and the twelve 150-foot-diameter tanks in just 19 months. This allowed McCarthy less than a month to pour each tank. McCarthy used special crane-set gang forms made of steel radius beams, aluminum beams, and plywood. Using enough forms for one and one-half tanks allowed reuse of the forms for all 12 tanks without causing delays in form setup and stripping. Read more

Features Tipping Floors Require Tough Toppings

After collection, solid waste is usually dumped on what are called tipping floors at facilities such as transfer stations, balers, and incinerators. Vehicles tip the garbage onto the floor and bulldozers or front end loaders push or scrape the material into pits. All this dumping, pushing, and scraping subjects floors to extreme abrasive forces of impact and attrition. Conventional concrete floors lose the top inch of their surface in a few months under these harsh conditions. Only metallic toppings, installed at 1- to 2-inch thicknesses, can withstand the daily abuse tipping floors receive. Read more

Features Contractors Play Key Roles in Expanding Tilt-Up Construction

The history of tilt-up construction teaches us that it is the contractor who is primarily responsible for the successful introduction of the tilt-up technique into new markets. It wasn't until after World War II, when the country experienced a construction boom, that the tilt-up technique began to take off. The most dramatic boom was in Southern California, where contractors found tilt-up to be a cost-effective means of meeting the demand for new commercial construction. Contractors found they could erect buildings quickly and without skilled labor. Read more

Features Long-Boom Pumps Help Keep Sewage Treatment Plant Construction on Schedule

The Oceanside Water Pollution Control Plant is an immense project requiring 135,000 cubicyards of concrete. The plant is spread out over 12 areas of Pacific Ocean front, making multiple concrete pours necessary for nearly every working day. To achieve the goals of the project's general contractor of getting concrete to each pour location with a minimum of setup time and completing each pour quickly, a pumping subcontractor with long-boom equipment was brought in. Then the general contractor set up its own concrete crew rather than subbing out the work. Read more

Features The Parthenon: an Exact Replica of the Famous Greek Temple

In 1896, Nashville civic leaders planned an exposition that included the buildings of Egyptian, Greek, and Roman styles. A replica of the Parthenon in Athens, Greece, was built to house paintings and other works of art to be shown at the exposition. When the exposition closed, all the buildings were scrapped, with the exception of the Parthenon. But as the plaster facade of the Parthenon replica soon began to deteriorate, planning began for a permanent Parthenon replica. Read more

Problem Clinic Height Limits on Concrete Free Fall

We're placing concrete for a job with 10-foot-high columns, 18x18 inches in cross section. The columns contain four #8 vertical bars. The fastest way to place the column concrete is by direct discharge because there's an unobstructed path to the bottom of Read more

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