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A valve at the Pacheco Conduit inlet in California lets workers drain the conduit without draining the 5.3-mile-long tunnel that feeds it.
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Before welding insert plates to reinforcing bars, preheating is sometimes needed to help reduce cracking at the welded joint. But preheating is costly and complicates the welding process.
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Engineers are by nature a conservative lot. Buildings and bridges are designed to withstand loads from the expected and the unexpected. The same is not done when designing pavements: unexpected traffic volumes sabotage many designs.
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Joe Robbie Stadium, home of the Miami Dolphins, was designed with eight 29-foot-wide pedestrian ramps.
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Using a laser system is faster than optical grade leveling and requires fewer workers. To use it correctly, though, you need to understand how the system works and how to keep it in calibration.
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A geodesic dome requires no heavy equipment, uses locally fabricated materials, and delivers a strong, energy-efficient dwelling suitable for many climate zones.
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A remarkable concrete dwelling cut into a rocky ridge of the Arizona desert has won acclaim from many architects.
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Many concrete contractors must cope with cold weather effects on freshly placed concrete. Insulated curing blankets, used along with other cold weather procedures, can permit concrete work at temperatures as low as -25 degrees Fahrenheit.
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Cooled concrete played a big part in producing a nearly crack-free base mat for a Milwaukee high-rise building.
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About 1950, Frank Lloyd Wright designed a concrete masonry building system that he called Usonian Automatic.
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When you look at a concrete test report is your eye drawn immediately to the bottom line--cylinder strength? If so, you may miss valuable information.
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A six-level cast-in-place parking structure caused some problems for a Maryland forming contractor.
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During an inspection of the elevated deck for a 16-year-old parking garage, extensive cracking was found above all 14 interior columns.
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Trap rock and other materials such as quartz, emery, and metallic aggregates are often used in dry shakes to improve floor wear resistance.
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Buck Sweet, a poured wall contractor, makes wall forming and stripping as easy as possible for his crew.
Bleeding isn't always bad. It lowers the water-cement ratio and densifies the concrete. But concrete that bleeds too fast or too long can cause a number of problems.
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Back injuries are costly. Workers pay the highest price, enduring pain and coping with disabling effects.
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Almost everything in Mark Story's bathroom is cast-in-place concrete, including the walls, ceiling, floor, skylight well, tub, shower, and shelves.
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How do you place 12 inches of bedding aggregate and 6-inch-thick concrete slab on a 1-to-1 slope? It's hard enough to compact the aggregate, let alone deposit concrete on top of the bedding and keep everything from sliding when workers place and consolidate the concrete.
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Concrete pavement D-cracking is a terminal condition. Once it starts, there's no known cure. The cause is known--coarse aggregates susceptible to freezing and thawing deterioration. But the only way to prevent D-cracking is to avoid using these aggregates in concrete pavements.
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Artist Michael Wolk, an award-winning designer of furniture, graphics, and interiors, chose concrete for one of his largest and most public designs.
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A buy-sell agreement (sometimes known as a shareholder's agreement) provides for an orderly transfer of ownership of a closely held corporation.
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Landscaping offers a growth market for the concrete contractor as well as the precaster.
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It looks like a lawn but it performs with the structural capacity of a well-designed concrete slab on grade.
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A latex modified concrete (LMC) overlay delays the onset of corrosion by slowing movement of chlorides to the reinforcement.
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Regardless of the project size, a larger percentage of the money budgeted is being spent on landscaping than in past years.
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Choosing and paying a specialty contractor can be a painful experience. Owners want value for their construction dollars and specialists want a reasonable profit. Can they both be satisfied?
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Poorly cured concrete starts its life with a defect that could be fatal. Water-filled voids, instead of filling with hydrated cement, remain empty after the mix water evaporates. Avoiding this handicap requires the engineer to specify adequate curing and the contractor to use curing methods that...
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A floor joint is an interruption in an otherwise smooth surface. In an industrial floor, the joint needs to be protected from hard wheels. By filling rather than sealing it, you protect the edges of the joint from damage.
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A thorough investigation must be performed to determine the extent and magnitude of concrete distress. The typical investigation begins with a condition survey based on visual examination and soundings to identify delamination and deterioration.
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Most tilt-up contractors face the problem of casting wall panels with a total area that exceeds the footprint (ground floor area) of the building. For a four-story warehouse near Seattle, the available footprint was less than half the total square footage of the walls. Still, the architect chose...
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Concrete call-backs are more frequent in the residential market. What is surprising is that the same mistakes recur season after season, job after job. Careful planning and good workmanship can eliminate these mistakes and cut the number of call-backs.
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To control cracking best, reinforcement should be placed as close as possible to the concrete surface.
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Firing an employee for any reason or no reason at all can land your company in court. In today's lawsuits for wrongful discharge, documentation of employee performance is often the key in determining who wins a suit. The documentation must support the discharge without contradicting performance...
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About 400,000 lineal feet of control joints crisscross the concrete floors in Toyota's new 4,000,000-square-foot auto assembly plant in Georgetown, Kentucky. The Toyota plant joints were filled with about 6,000 gallons of semi-rigid epoxy joint filler.
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Located at the University of Calgary, Calgary, Alberta, the Olympic Oval is an award-winning building. Its unique roof system of diagonally intersecting precast concrete arches won a 1987 Prestressed Concrete Institute (PCI) Design Award and a 1987 Post-Tensioning Institute (PTI) Award of...
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To show that a concrete overlay is an effective repair for distressed asphalt pavements, the Kentucky Ready Mixed Concrete Association (KRMCA) whitetopped a deteriorated asphalt entrance drive to a shopping center.
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Plastic shrinkage cracking is a potential problem when latex modified concrete (LMC) is placed on a dry, windy day.
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Concrete repairs sometimes fail because bond between new and old concrete fails.
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Concrete slab settlement causes problems. But slabjacking, properly done, solves the problems permanently. It's faster and much less costly to raise a concrete slab than to replace it.
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Brandywine Shoal Lighthouse stands 7 miles west of Cape May, New Jersey. It is the first reinforced concrete structure of its kind located on a submarine site in the continental United States.
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Parking lots are a cost effective alternative to asphalt that saves owners money in lifetime costs. To encourage good construction of concrete parking lots, the American Concrete Institute (ACI) formed Committee 330, Parking Lots, in 1982. The committee's first document, "Guide for Design and...
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Single strand tendons offer an efficient, economical, and practical way of post-tensioning many types of building structures.
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Bonding fresh, plastic concrete to old, hardened concrete increases the strength of the composite material. Bond is not, however, guaranteed. It must be ensured throughout proper surface preparation, material choice and use, and curing.
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Accidents in the construction industry cost $8.9 billion, or 6.5% of the total annual construction dollars.
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Daily rainshowers, peat bogs, and heavy, wet clay didn't dampen efforts to create a 4.5-acre concrete tropical landscape in less than 7 months for a Puerto Rican hotel.
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Salty sea air made the rebar corrode in decorative precast concrete balcony facings of an 18-story coastal condominium in La Jolla, California.
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Unless concrete is properly consolidated, voids reduce strength regardless of the water-cement ratio. Consolidating the concrete, usually by vibration, increases concrete strength by driving out entrapped air. It also improves bond strength and decreases concrete permeability.
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Mother Nature's palette comes alive in architectural concrete through the exposure of aggregates...quartz, granite, obsidian, basalt, limestone, and many more.
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In order to function properly, vertical and horizontal construction joints must be carefully located and built correctly.
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The Federal Highway Administration's (FHWA) crowning achievement in 1982 was adding a nickel to the federal fuel tax.
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Pumping concrete through a separate placing boom has replaced crane-and-bucket methods on many high-rise construction jobs.
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Inter-Continental Peace Bridge, Inc., was organized in 1968. The purpose and vision of this organization is to join the continents of the world by connecting the shores of Alaska and Siberia.
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For low-rise multifamily homes, concrete or concrete-masonry construction costs only slightly more than wood-frame construction.
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The most direct route for pumping deck concrete was through the lobby of Metropolitan Square, a 42-story St. Louis office building.
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The cost of maintaining worn-out streets eats up so much of a city's limited funds that often little is left to invest in reconstruction.
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A new system for recycling returned ready mixed concrete has been developed.
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Florida design/build construction firm R.J. Prossen, Inc., saves its clients money by combining modular design, tilt-up construction, and standardized details.
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Home buyers surveyed ranked ample storage space as the most desirable feature in their homes. Rooms that can easily be adapted to more than one use are the second most desirable feature. Full basements provide both of these features.
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Concrete high-rise buildings offer lower costs over the entire life of the structure.
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Tilt-up combines fast, economical construction with all the advantages of concrete: economy; speed of construction; design freedom; security; and use of local materials. Added to these advantages are concrete's durability, fire resistance, low insurance rates, and energy efficiency.
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A new pinnacle on the Manhattan skyline, City Spire at 146 West 56th Street received the 1987 annual award of the New York Concrete Industry Board for overall excellence in quality of design and construction of buildings and structures using concrete as a material.
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The use of inflated forms has grown steadily. A single form can be adjusted to build many sizes of culvert arch or other structures such as large-diameter concrete pipe, tunnel linings, and water tanks as well as earth-sheltered buildings.
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Post-tensioned domes designed to support stored materials can be built using inflated forms.
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Every chimney that lacks a masonry liner or has a cracked liner, that has loose mortar joints or damaged brickwork, or shows signs of creosote staining can be viewed as a potential fire hazard. A new refractory concrete lining of the proper size can provide a smooth, seamless acid-resistant flue...
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Inflated forming techniques coupled with a better understanding of ground temperature control are responsible for a new generation of earth-sheltered buildings.
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Concrete shells 50 feet or more in diameter can be built at low cost by two persons having only limited construction skills. This method requires no steel reinforcement and is simpler than shotcreting methods.
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In the 1960s the first successful attempt was made to use low air pressure to lift and shape in a single operation all of the concrete and steel needed for a 300,000-cubic-foot dome large enough to contain an entire gymnasium. Refinements since then result in the construction steps shown.
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Preliminary design of a reinforced concrete structure involves the selection and representation of a framing scheme, showing size and shape of beams, columns, and slabs.
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Operating boomed vehicles close to overhead power lines puts operators and nearby workers at risk of electrocution.
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Air forms may be full or partial spheres, ellipsoids, cylinders, and varied mix-or-match combinations of these shapes. Irregular or free-form shapes also can be used.
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Spray a shell structure onto the inside of an inflated balloon--first some layers of urethane foam, then some layers of shotcrete.
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Commonly used air-entraining agents, whether vinsol resins or multicomponent organic materials, usually reduce concrete strength.
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A payment method used on one Medina County, Ohio, whitetopping takes some of the guesswork out of estimating and bidding concrete overlays.
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A system developed in Austria for forming axially symmetrical curved structures such as funnels, cones, shafts, sewage digestion tanks, and water towers permits continuous placement of concrete without form ties.
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Wet-mix shotcrete is more commonly used for high-production shotcreting applications than for repair jobs. But a Chicago-area contractor has designed and produced a wet method shotcrete machine specifically for repair work.
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Two developments have made possible the new generation of high-strength concrete now available for routine construction: superplasticizers, and silica fume.
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Joints should be sawed in concrete slabs before drying or cooling causes random cracking.
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Sure, concrete can fly--with the help of a helicopter, a fearless pilot, and an experienced ground crew.
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Major categories of accidents in forming and shoring activities are: falling from one level to another; being hit by falling objects; improper lifting practices.
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Every building constructed using concrete in any shape or form has cracks. It is the size, frequency, and reason for their existence that matters, not that they happen to occur.
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One, two, three. Dig a trench. Erect the precast wall panels in the trench. Then fill the trench with concrete.
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Why recycle concrete pavements? The key reasons are cost savings and reduced environmental impact.
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Cathodic protection (CP) stops corrosion and eliminates the need for periodic patching or deck replacement. Improved materials and methods have reduced costs and simplified installation of CP systems.