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After only 10 years of service, the roof of a 15-million-gallon reservoir in Greeley, Colorado was near collapse. The reservoir was originally designed and built as a partially buried tank with an exposed post-tensioned concrete roof. The concrete had been exposed to Colorado's extreme temperature...
Planning and coordinating a tilt-up project should be a team effort involving the architect, engineer, and the contractor. Preconstruction meetings are a good way for all parties involved in a tilt-up project the iron out details before work begins.
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Understanding how seawater deteriorates concrete and carefully selecting a mix design can help ensure the maximum service life of the concrete surface. Concrete exposed to seawater may deteriorate from the combined effects of chemical and physical processes. Attack is slowed by reducing concrete...
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Welded wire sandwich panels were the framework and structural reinforcement for an adaptable concrete construction system selected by the Habitat for Humanity volunteer group's traveling work camp series in the summer of 1991. Working on 14 previously prepared foundation floor slabs, the volunteers...
After two of four planned Detroit high-rises were built with steel frames, owners began to hear concerns from tenants about wind-induced movement at the upper floor levels. To resolve this problem, the designer of the third high-rise decided to use a concrete frame. By switching to concrete, the...
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The performance of any form sheathing, whether made of plywood, metal, or fiberglass, is only as good as the performance of its support members. Form support is provided by various components. For wall panels, studs supported by cross members called walers provide direct support. For horizontal...
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Lightweight aluminum wall forms and a "pour down" sequence contributed to the successful construction of the 44-story Nauru Tower. The tower is a mixed-use structure with the first five levels of retail and commercial space requiring special architectural treatment. Concrete for the 39 residential...
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Concrete contractor Landavazo Bros. Inc., Hayward, California, recently fulfilled a contract to place and pump the 110,000 cubic yards of concrete needed for the expansion of San Francisco's Moscone Convention Center. The 100-million-dollar project involved construction of a 487,500-square-foot...
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To build the roller-compacted-concrete (RCC) Cuchillo Negro Dam, PCL Civil Constructors Inc. used a conveyor system that delivered the RCC mix from the mixing plant to the dam site. The 1,500 feet of conveyors with a maximum belt capacity of almost 9 cubic yards per minute delivered the RCC mix to...
In a pump line, concrete moves in the form of a cylinder or slug separated from the pump line wall by a lubricating layer of water, cement, and fine sand. To keep moving through the line, the mix must be dense, cohesive, and have sufficient mortar. When concrete is pumped, if spaces or voids...
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On an average job, how often should slump and air content tests be made? How many test cylinders should be made?
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Profits can be made in the curb and gutter, sidewalk, bridge parapet, and median barrier markets if you have the right paving equipment. The Concrete Paver Bureau within the Construction Industry Manufacturer's Association (CIMA) has grouped paving machines into three categories: curb and gutter...
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To be a successful concrete promoter requires a little motivation and a lot of hard work. The first thing you must determine is if you really want to promote concrete. Although it sounds silly, the truth is if there isn't a producer who's willing to supply the concrete when it's needed, paving...
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Contractors looking for a market niche might consider going after paving jobs that aren't suited for slipforming but can be done with side forms. Steel side forms are a smaller investment than slipforms, and they pay for themselves more quickly. Cities and counties are replacing asphalt pavements...
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Mr. and Mrs. Warren Langford wanted the steps and sidewalks leading to their palatial dream home in Frontenac, Missouri, to be as dramatic as the home itself. But they also wanted to use a material that was economical. So, as a low-cost alternative to stone, they chose concrete, imprinted to...
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Homeowners can take measures to ensure good performance and prevent problems with their concrete foundations and flatwork. To avoid wall cracking, the builder should have sloped the soil at least 1 inch per lineal foot of run while soil grading around the house was being done. That slope should...
One hundred years ago, a Bellefontaine, Ohio, chemist named George W. Bartholomew attempted to solve a dust and mud problem.
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The concrete industry felt the thrill of victory when Medicine Hat, Alberta, decided to replace deteriorated asphalt intersections on the Trans-Canada Highway with concrete. Robert Seme, regional paving engineer of the Canadian Portland Cement Association's western region, calls the project "the...
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Designing and building the Bourse Garage and theater complex in part of Philadelphia's old city presented contractors with a challenge. Narrow streets, limited site access, a high water table, and making the building fit with the nearby historic buildings were some of the obstacles contractors...
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The concrete industry is concerned that it may lose more of its already small concrete paving market because mechanistic design methods used in Illinois may spread to other states. Mechanistic methods used by the Illinois Department of Transportation (IDOT) require thicker concrete pavements than...
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Properly using internal vibrators to consolidate concrete can help minimize honeycombing, pour lines, vibrator burns, excessive bugholes and other defects. This article sets forth the author's ten rules for using an internal vibrator correctly.
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The challenging roof design of the Shiley Eye Center, University of California San Diego, required the use of custom-built formwork. The design of the 160-foot-long, 30-foot-wide roof called for arched joists having thickened center sections. The joists and beams also required an architectural...
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Many developments in shotcrete technology during the 1980s have enhanced shotcreting capabilities. Today, both dry- and wet-mix shotcretes often contain supplementary cementing materials, which improve shotcrete workability and performance.
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A massive concrete foundation mat pour for a multiuse building complex in Newport Beach, California, presented contractors with a challenge. The mat, which varies from 3.5 to 8 feet thick, had to be placed over a quagmire 21 feet below sea level. To prepare the extremely wet site for concrete...
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FNF Construction Inc. is using cement-stabilized alluvium (CSA) to channelize the Rio Salado's flow through Tempe, Arizona. By mixing portland cement, Class F fly ash, and native river bed (alluvial) soil, FNF is producing a CSA end product. While CSA is not new, using the extra-coarse alluvial...
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Concrete canoe racing is an opportunity for engineering students to learn about putting theory into practice, as well as how to work together as a project team. The idea for a concrete canoe race was spawned in 1970 when University of Illinois professor Clyde Kesler had his civil engineering honors...
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Unfortunately, far more highway bridges in the United States are "substandard" than are able to be repaired. A common sign of bridge deck wear is loss of skid resistance, which often becomes evident when water collects on the bridge deck. Bridge deck designers usually try to minimize water...
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Concise, complete daily reports have many uses that more than repay the cost and effort involved in preparing them. The daily report provides an objective history of the entire project. It should be used as a tool for managing the current project and planning the next one. Data provided by...
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The Cassair Connector Project, a 100-million-dollar upgrade from arterial city street to freeway, made use of both precast and site-cast concrete in several different structures. The largest concrete structure in the project is a 2,394-foot-long reinforced concrete twin-arch tunnel. The tunnel has...
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Using a separate placing boom can help you realize a profit by making it easier for you to get a high-rise project done well in the least amount of time possible. Adding a separate crane may fill the obvious gap that allows you to meet your schedule, but it may also have a ripple effect on overtime...
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Many contractors find that they don't make money on small pours. But increasing profits on small pours simply requires a little more planning. Don't just take cost into consideration when planning a small pour. Make sure the concrete placement equipment can fit through the openings and can be moved...
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Converting crawl space to usable space in a 70-year-old school building turned into a major headache for the project's engineer and contractor. During excavation of the crawl space, workers discovered that pad footing elevations for two old columns were higher than the new basement floor elevation...
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Tilt-ups have historically done well in seismically active areas. Structural engineer High Brooks, author of "The Tilt-up Design and Construction Manual" says "there's not a single known instance of an in-service failure of the estimated 10 million tilt-up panels constructed to date." This...
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Joints are critical to the performance of concrete parking structures because they allow movement caused by temperature change, drying shrinkage, and creep. Three types of joints are commonly used in concrete parking decks. Control joints, sometimes called contraction joints, are used on parking...
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Ten Commandments for architectural concrete contractor's.
Artist Kathy Goodhue, Dublin, Ireland, switched to concrete as a sculpting material after experiencing dissatisfaction with using metal and wood. She found that concrete was less costly and allowed her greater creativity with her color and texture needs. Despite the large scale of most of her...
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In Calgary, Alberta, most ready mixed concrete producers also run at least two concrete pumps. Yet 160 miles up the road in Edmonton, not one concrete producer runs a pump. All the concrete pumping is done by pumping contractors. U.S. producers pump concrete for several reasons. Meyer Material Co...
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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...
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:
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...
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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...
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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...
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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...
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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.
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Is there a publication that explains standard aggregate tests in an easily understood manner? The ASTM standards for specific gravity, abrasion resistance, sieve analysis, and similar tests are hard reading.
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The four-lane Jamestown-Verrazano bridge linking North Kingstown and Jamestown, Rhode Island, underwent a 2,400-ton precast bridge span lift between 1990 and 1992. The double-cell box girder used for both the high-level approach spans and the main structure varies in depth from 10 feet to close to...
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A formwork system moved by forklift rather than by crane was used to build the upper ramp of a two-level, 1,250-car cast-in-place concrete parking garage in Milwaukee. Because of the large area covered by the post-tensioned, slab-and-beam ramp, the contractor had to find an efficient way to...
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Computers are becoming necessary pieces of equipment in the contracting business because they can enhance speed, quality, appearance, and efficiency. Computer-generated documents convey much more attention to detail and professionalism than do bids scribbled on the back of an envelope.
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The small size of the concrete pumping industry hasn't justified much software development. But two specialized software packages are available. The industry standard software runs on any IBM-compatible computer and is composed of modules - disks containing instructions for the computer to perform...
The Ohio State University football stadium was last repaired extensively in 1948, leaving unsightly dark, irregular patches. Numerous stains, spalling concrete, and exposed steel reinforcement called for further repair of the concrete facing. Most of the precast cornices and all the precast window...
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The thin-shell concrete dome topping the Sundome in Yakima, Washington, has 24 wedge-shaped segments arranged in a radial pattern like the pieces of a pie. But only six wood forms were needed to cast the 24 segments because of an innovative rotating forming and shoring system. The Sundome roof has...
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With its enactment of the Budget Reconciliation Act on September 5, 1990, Congress has increased maximum Occupational Safety and Health Administration (OSHA) penalties a whopping sevenfold. The maximum penalty for a willful or repeated violation is now 70,000 dollars, up from 10,000 dollars, and...
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Using fixed weights of variable ingredients under variable conditions yields a predictable result - a variable product. To avoid problems caused by keeping ingredient weights constant, concrete should be produced to meet performance requirements in accordance with a design formula for the composite...
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Contractor Ken Macaire, based in Los Angeles and Sherman Oaks, California, uses custom carving to create regionally accurate concrete waterscapes for residential and commercial use. Santa Barbara developer John Lucian said a water feature adds one-third more to the property value. There are two...
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The February 1989 issue of "Concrete Construction" contained a nomograph for use in estimating the volume of concrete needed for slabs of varying thickness and area. Joseph Deigh, a retired civil engineer, devised the nomograph so contractors could quickly determine concrete volumes on the job...
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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...
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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...
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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...
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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...
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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...
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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...
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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...
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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...
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Backfilling is all too often the beginning of basement destruction. But the problems associated with improper backfilling can be avoided by taking a few simple precautions.The four key elements to backfilling are:
Settlement of building foundations can often be arrested and the building restored to near its original condition by using proprietary underpinning systems. The systems increase foundation load-bearing capacity with steel piers that are pushed or screwed into the ground beneath the footings or...
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An increasing number of highway engineers are choosing polymer concrete for concrete bridge deck rehabilitation, finding that its advantages as an overlay material justify its high cost. A polymer concrete overlay not only improves the abrasion and skid resistance of the deck surface, it also...
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Specifications often require a two-step procedure for sawing contraction joints in concrete pavements. The first cut, called a green cut, is made with a one-eighth-inch-thick blade that cuts through one-quarter the slab thickness. Green cutting is done as soon as possible to induce cracking through...
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Ray Heid Construction Ltd., St. Clements, Ontario, Canada, finished a 65,000-square-foot concrete driveway and parking lot in just 3 days using a power screed mounted on skis. The skis enabled workers to control screed elevations without the need for rails, forms, or other screed guides. The...
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On construction jobs requiring overhead access, a self-propelled aerial work platform can be a cost-effective, efficient way to transport workers and tools to the work area. Of the four major types of aerial work platforms, telescopic booms and telescopic articulated booms are the most effective...
Leave-in-place concrete screed rails have been used most commonly in slab-on-grade work, but now the rails are being used for elevated slabs on metal decks. Instead of using wet screeds for elevation control, contractors fasten high-strength concrete screed rails to the deck. This permits the use...
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Construction time and cost were reduced by using precast concrete to create an elegantly proportioned and detailed entrance bridge for an upscale Florida subdivision.
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Trompe l'oeil, or fool the eye, is a style of painting in which architectural details or scenes are depicted with photographic clarity. This style, used centuries ago by Roman nobility, is now enjoying a resurgence in the United States. A leader of this revival is Richard Haas, an internationally...
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The author of this article, an Australian, formed a tilt-up construction company called Advanced Building Systems Party Ltd. after seeing many tilt-up innovations in the United States. His next step was to gain the acceptance of the Australian market for the tilt-up system. He decided to design and...
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Fire fighters have wondered if the roof support system in tilt-up buildings burned down, would the walls collapse? They didn't in March 1986 when a severe fire in a Phoenix tilt-up building consumed the entire wood roof system. The building, a U.S. postal annex built around 1970 was constructed of...
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Frustrated too often by Lansing, Michigan's winter weather, Larry Clark of L. D. Clark Building Co. decided to do something about it. After a year of planning and preparation, his solution is anair-inflated dome enclosing and supporting its own working environment. Regardless of theweather, inside...
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Most contractors and engineers agree that elevated concrete slabs don't always deflect as intended. Measurements are necessary to identify the areas in which practice departs from theory and to determine what adjustments are needed to improve the quality of the next concrete slab placement. A...
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Several hundred people die each year in trench collapses. Unfortunately, production and safety goals seem to be at odds when dealing with trench work. The soil that snuffs out life in a trench collapse is not only suffocating, it is crushing, weighing easily 120 pounds per cubic foot. To put that...
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A passivating oxide layer protects embedded steel reinforcement from corrosion. Over time, however, chloride and carbonation can cause the passivating oxide layer to deteriorate, leaving rebar open to corrosion. One way to rehabilitate concrete that has been corroded by carbonation is to remove the...
The increasing popularity of golf in this country could be big boost for the concrete paving industry. This is because many new golf courses are installing paved pathways for golf carts. To allow concrete contractors to take advantage of this market, a company recently developed a narrow-width...
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Diversified Concrete Cutting, Sparks, Nevada, found itself facing dust problems when it attempted to clean sawed joints along I-395, just north of Reno, using conventional abrasive blasting methods. Contract specifications originally called for sandblast cleaning of expansion joints before sealing...
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Controlled permeability formwork (CPF) can increase concrete durability in the critical cover zone, improve surface appearance, and reduce formwork pressures. The system is comprised of a filter, drain, and structural support. While the concrete is being compacted, air and some of the mix water...
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Concrete sculpture may be done by carving, direct modeling, casting in a mold, or casting on a bed of sand. Brian Adddis has tried them all. The sculptor of "Abstract Form," a 15-foot-high creation standing on the grounds of the Portland Cement Institute of South Africa in Johannesburg, is devoted...