January 1991 Table of Contents

Features A Concrete Lotus in India

The lotus flower is a symbol of purity in eastern religions. It is not surprising then that Iranian-born-and-educated architect Fariburz Sahba chose the flower as the design concept for the Baha'i House of Worship near New Delhi, India. The temple was designed in the shape of the newly opened flower. Over the central hall, a double-layered, 112-foot-diameter inner dome composed of 54 concrete ribs with concrete shells between rises 92 feet above white marble floors. The first of three layers of nine petals arches over the dome, 110 feet above the hall, the tips parted to allow natural light to penetrate the interior through glazed roof panels. The bases of the inner petals form nine arched portals leading from a raised entryway created by the second set of petals. Read more

Features Concrete Sphere Houses French Planetarium

A 66-foot-diameter concrete sphere, flanked by a curving wall 26 feet high and 262 feet long, is the architectural focal point for a new technical-vocational school in Montpellier, France. The concrete shell will house the school's planetarium. The segmental wall and adjoining sphere at the Jean Monnet school were built in 4 months, using a standardized proprietary forming system adapted for the project. The entire formwork operation was done by a crew of five with one experienced supervisor. Read more

Features Construction of Elevated Concrete Slabs

To avoid getting burned in a dispute over slab tolerances, engineers and contractors need to know how design and construction decisions affect variations in slab dimensions and locations. Read more

Features Weathering of Concrete

It doesn't have to be more expensive to produce good-looking concrete buildings than to produce bad ones. What is needed is care in studying the rainwater flow over the facades, with attention to details to direct the flow properly. Rainwater initially acts as a natural cleanser as it hits a building. But as it flows over a surface collecting dirt, it is likely to deposit this dirt on adjacent surfaces. Absorption, porosity, and texture of the concrete will affect how much this rainwater affects the surface. Both small and large architectural features, such as the the slope of an exposed architectural surface, also affect the flow of rainwater and its affect on the concrete surface. Read more

Features Colorado Tests Whitetopping for Asphalt Road Rehabilitation

To reduce time caused by road rehabilitation, highway engineers are giving more attention to whitetopping - placing an unbonded concrete overlay over deteriorated asphalt - as an alternative to reconstructing roads or resurfacing them with asphalt. The Colorado Department of Highways (CDOH) is evaluating whitetopping as a possible solution to the state's road rehabilitation problems. On June 2, 1990, it participated in a test project involving the whitetopping of a section of Harmony Road in Fort Collins. Concrete overlay sections of 3.5 inches thick and 5 inches thick were placed. For the next few years, the CDOH will monitor the performance of the two overlays. Read more

Features Concrete Mix Design

The goal of any mix design is to produce a concrete that will meet performance requirements for the specified conditions and use. "Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete" is the most widely used guide for concrete mix design. The major steps involved in this method are as follows: Read more

Features Concrete Bridges on the Historic Columbia River Highway

Attorney and entrepreneur Samuel C. Hill was a primary mover in the struggle to get a motor road built through the Cascade Mountains from Portland toward eastern Oregon. In 1906 Hill invited Samuel C. Lancaster, an engineer who had gained recognition for the design of a network of county roads in Tennessee, to the Northwest. As their acquaintance grew, Hill decided that Lancaster was the man who could design and build the highway that Hill had dreamed about. The project began with a survey in September 1913, and grading was started in October. Read more

Features Collecting What You're Owed with Mechanics Liens

When you've built improvements to someone's property, but the owner or general contractor has not paid for them, you still own them. If you aren't paid, you can retrieve the value of your property by foreclosing on the loan. If by agreement you've provided labor or material that was incorporated into (and presumably increased the value of) real estate or improvements to it, you have a mechanics lien on the improved property. The lien comes into being by "action of law," that is, automatically. But certain steps must be taken to make the lien enforceable. Lien statutes are construed strictly, against the lienholder-concrete firm. Because of this strict construction of the statutes, the details for perfecting your mechanics lien cannot be standardized over a large, multistate area. Read more

Features New Construction Method for Arch Bridges

A Japanese builder is using a new construction method called concrete lapping with preerected composite arch (CLCA). CLCA eliminates the shortcomings of the traditional arch construction methods and meets stringent cost and scheduling requirements. P. S. Concrete Ltd. of Tokyo has used CLCA to construct two bridges in Japan - the Asahi Bridge and the Joshi Bridge. Both bridges took two 8-month construction seasons to build. Read more

Features Buy, Lease, or Rent?

The decision to lease or buy is one of economics. With many variables involved in a lease or outright purchase, it is not easy to determine the best deal. When a company leases equipment, it typically uses a financing lease. Normally there is no down payment. The contractor then makes payments to a third party finance company. An alternative is the service or operating lease. Under this lease, the lessor (manufacturer or seller) remains the owner of the property and is responsible for the payments of any taxes or maintenance. This leasing option allows contractors to rent the equipment for a shorter, more flexible period of time. Read more

Features Repetitive Motion Injuries: a Growing Employee Health Concern

The cumulative physical stress of job-related tasks, such as repetitive motion injuries, has made ergonomics an important workplace issue for the construction industry in the 1990s. Ergonomics is the science of tailoring work and workplace to the physical needs of the worker. In the construction industry, such maladies as carpal tunnel syndrome, back pain, and "vibration white fingers" have alarmed safety officials. To help employers deal with repetitive motion injuries, the Occupational Safety and Health Administration (OSHA) issued voluntary guidelines. If the voluntary guidelines become accepted by most industries, they may evolve into a federal safety law. Read more

Problem Clinic How Soon to Place Wall and Column Concrete on Top of Footings and Slabs?

Two similar questions have been raised regarding placement of concrete on top of recently completed slabs and footings. In one case the contractor wanted to form and place his basement walls the day after completing the footings, but was being required by Read more

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