50 years of Concrete Construction progress: people, projects, materials, equipment, and...

Progress is like people walking to their departure gate in an airport--some stroll along as if time is of no concern, confident they will get there on time, others frantically rush ahead swerving around the slowpokes, no time to spare. Progress in the concrete industry too has been slow in some

When the first issue of CONCRETE CONSTRUCTION was published in September 1956, the world and concrete construction were very different. There was no post-tensioning, no laser screed, few admixtures. To examine the progress we have made, or not made, we've asked some industry leaders (see page 7) to comment on different aspects of the past 50 years in the concrete construction industry. We've also looked at some of the people and projects that have made a difference. Unfortunately, there isn't room to cover everything, but we hope to give you a glimpse of where we've come from and where we are going.--The editors

High-strength concrete

For a concrete man, Chicago was a great city in which to work and learn. Beginning my concrete career in the early 1960s and joining Material Service in 1970, I was fortunate to be a part of the birth of high-strength concrete. For us in Chicago it has always been obvious that the development and use of high-performance concrete was the result of a concrete community--city engineers, developers, structural engineers, contractors, concrete producers, material suppliers, and testing labs-working together. Material Service employed a full-time structural engineer, Jamie Moreno, whose job was to investigate and promote the use of high-strength concrete. Material Service and Jamie Moreno spearheaded this venture into one of the more exciting eras in concrete history.

The evolution began in 1965 with the production of 6000-psi compressive strength concrete. In the 1970s came 7500 and 9000 psi, in the 1980s--11,000 and 14,000 psi, and by the 1990s--18,000 psi. This fulfilled a 1965 plan. By design, every job was used to investigate the next higher strength. Either a couple of columns were poured using higher strengths than required, or in situ tests were conducted to measure such attributes as creep or the effect of temperature. By the time the next high-rise was on the drafting table, all interested parties had enough data and confidence to justify using higher strength concrete. The results of all these tests and experiences were shared with the entire concrete community. No single company benefited. Such cooperation is rare in any industry.

I believe there is a very important underlying issue to be recognized. We, as members of this community, have a responsibility to donate our time, knowledge, experience, and even resources, to help our industry continue to develop new and exciting products that will enhance the future of our livelihood--concrete.--John Albinger

Admixtures

When the first issue of CONCRETE CONSTRUCTION hit the streets in 1956, concrete producers began leveraging the benefits of air-entraining and water-reducing admixtures to improve the buildings and infrastructure where concrete was called on to perform. While the earliest water-reducing admixtures date from the 1930s and 1940s, liquid water-reducing and retarding admixtures were introduced in the 1960s. Increased workability, lower water/cement ratios, higher strengths, and additional control over setting time allowed placement in a wider range of temperatures, further expanding the market and marketability of concrete.

Research and development led to significant advances in admixtures during the last two decades of the 20th century, resulting in dramatic improvements in concrete construction. The first generation of high-range water reducers, used to produce flowing concrete, were introduced in Japan and Europe in the 1960s, and the United States in the early 1970s. New developments in "next generation" high-range water reducers dispersed cement particles in concrete mixes more effectively than naphthalene or melamine-based superptasticizers, improving the placeability and in-place engineering properties of concrete.

In the late 1980s the pace of innovation accelerated. Corrosion-inhibiting admixtures increased the service life of concrete structures, protecting steel embedded in concrete exposed to chloride ions. A new family of admixtures, midrange water reducers, was developed, facilitating production of concrete in the 3- to 8-inch slump range with greatly improved finishing and pumping characteristics. Most recently, the development of polycarboxylate superplasticizers has allowed concrete producers to begin producing self-consolidating concrete.--Mike Shydlowski

PROJECTS THROUGH THE YEARS

Chapel of the Holy Cross, Sedona, Ariz., 1956

Built in the rugged desert terrain, this chapel s dominant element, the 90-foot-high cross, is also its major loadbearing structural element and extends 30 feet below the main floor into a cleft between the surrounding buttes. The interior, exterior, ramps, and retaining walls were all built with reinforced, sandblasted, integrally colored concrete.

Quantum Leaps in Slab Construction

When I think back on changes in concrete slab construction during my 50 years, nothing stands out like three inventions of the 1980s that changed the way we constructed slabs: the laser screed, the riding trowel and float dishes, and the early-entry Soft-Cut saw.

With vibratory truss screeds and other equipment, we typically placed slabs in narrow strips that limited the amount of slab we could place in a day--a 10,000-square-foot placement was large. The laser screed allowed much larger, more block-like placements that were far more level than before; our FL numbers increased at least 50%. Soon we were placing 20,000 to 50,000 square feet at a time with far fewer construction joints.

The ability to strike off much larger placements would not have been as beneficial if we had to continue using walk-behind power trowels. Riding trowels were the perfect accompaniment to the laser screed because we could finish much larger areas with less labor. We also increased the flatness of the floors, especially after the introduction of float dishes (pizza pans). Our FF numbers jumped at least 30% with proper use of riding trowels and float dishes.

I did much of the early investigation into the Soft-Cut saw for ACI 302 in the late 1980s and early 1990s. We successfully sawed and prevented out-of-joint cracking in slabs from 4 to more than 12 inches thick, even though we had the saw cut as shallow as 5/8 inch. The saw enabled us to cut much earlier than the wet cut saws we had been using for decades, minimizing cracking and saving overtime.

These innovations were conceived and developed largely by concrete contractors. And improvements have continued, enabling us to have greater productivity and quality of slab construction.--Jerry A. Holland

Concrete Forming ... It's Still About Productivity

The last 50 years have seen significant changes in the formulations of concrete, but one thing hasn't changed: concrete forming technology is still all about productivity. Arguably the greatest single innovation in concrete forming was the introduction of the SteelPly System by Symons Corporation in 1955. Steel-Ply's dramatic productivity enhancement over job-built forming, plus it's modular design with steel frame and specially-manufactured plywood, wedge bolt locking system, and ability to be renovated affordably caused it to become the industry standard. The time and expense of job-built forming is now a rarity.

About 15 years ago, visitors to the World of Concrete were given their first look at the highly-engineered steel forming systems then in use in Europe. Prior to that, the domestic heavy forming market was dominated by EFCO and the Symons. Since then, a literal "European Invasion" has taken place, with systems being imported by Doka, Peri, Meva, and Hunnebeck--all from Germany plus AlisPly (Symons) and ULMA, imported from Spain. These systems, which are generally assembled into a gang form and thus are productive for larger pours, all require a crane on the jobsite, common in Europe but less so in the U.S. Recently some of these companies have begun to develop lightweight versions that can be hand set.--Bill Kimball

PEOPLE WHO CHANGED US NORM SCOTT

Besides being a PCI Fellow and recipient of its Medal of Honor, ACI president and honorary member and instrumental in starting the ACI certification program, general manager of Wiss, Janney, Elsmer Associates, and founder of Consulting Engineers Group, Norman Scott made other significant contributions to the industry in the areas of trust and responsibility. "I think that trust--having the confidence in the people that you are dealing with as customers, competitors, and colleagues--is so important," he said. And he practiced what he preached, significantly advancing the collaboration of PCI with PCA and ACI, and internationally with CPCI and FIP.--Susan Clancy

PROJECTS THROUGH THE YEARS ACI Headquarters, 1958

Exposed architectural concrete for walls and roof defined the headquarters of the American Concrete Institute in Detroit. Designed by architect Minoru Yamasaki and built by Pulte-Strang, Ferndale, Mich., the concrete roof is a folded plate that cantilevers off the central corridor. ACI has since moved headquarters to a new building in Farmington Hills, Mich.

Slipform Paving

The advent of slipform paving gave contractors the ability to produce high-quality concrete roads using moving forms technology. Electronic controls and microprocessors have greatly improved the way slipform pavers operate, with great advances in control systems, which today feature self-diagnostics and intelligent electronic-over-hydraulic control. The increasing demand for better quality roadways continues to drive the research and development for machines to produce a smooth and durable pavement.

No one could have imagined 50 years ago the amount of truck traffic on today's road system. Maintaining and rebuilding today's roads has driven the industry to be more creative. Today, we can slipform a four-lane, 50-foot wide road in a single pass. I think the workers of the past would be very impressed with the quality we achieve today.--Gary Godbersen

Fiber Reinforcement Makes Good Concrete Better

The concrete industry was introduced to the benefits of synthetic fiber reinforcement a quarter of a century ago. Since then, the industry has embraced this valuable technology in numerous applications. Its steady growth is attributed to the time and labor savings as compared with placing alternate reinforcement materials and the additional concrete property benefits.

Synthetic microfibers are manufactured from synthetic materials and must tolerate the long-term alkaline environment common to concrete. Early-age concrete that uses these fibers has reduced shrinkage and settlement cracks.--Dennis Hogan

PEOPLE WHO CHANGED US ARMAND "GUS" GUSTAFERRO

It takes an alphabet of acronyms to describe Gustaferro's contributions to our industry. At PCA he headed the fire research laboratory. For PCI he was the chairman of the Technical Activities Committee and authored the manual, Design for Fire Resistance of Precast Prestressed Concrete. For CRSI he prepared Reinforced Concrete Fire Resistance. For NPCA he wrote the NPCA Quality Control Manual for Precast Concrete Plants. For ACI he taught troubleshooting seminars and wrote the first Concrete Craftsman Series booklet, Slabs on Grade. And for the WOC, at its inception, he told the founders, "If you're going to run a trade show, you have to conduct seminars," and he subsequently addressed more than 30,000 attendees over 29 years as World of Concrete's most popular speaker.--Susan Clancy

PROJECTS THROUGH THE YEARS Sydney Opera House, 1967

A troubled project from the start, the cost of the Sydney Opera House ballooned from an estimated $7.2 million in 1957 to $120 million upon completion in 1973. The original design by Joern Utzon was determined to be unbuildable. Despite the difficulties, this internationally recognized monument to perseverance and innovation still graces Sydney's harbor.

The hardened state features shatter resistance, increased impact and abrasion resistance, and lower permeability.

Fiber reinforcement has been used widely in slab-on-ground construction, but has expanded into other applications. Among the most appropriate and appreciated applications are elevated metal deck assemblies. The economics of pumping concrete that includes a hybrid system of fiber reinforcement as opposed to the time and labor intensity of hoisting and placing alternate reinforcement is significant.

Lift-slab Construction

In May 1958 CONCRETE CONSTRUCTION covered a project that used the lift-slab method of raising floors, first introduced in 1950. Through the years we followed the progress of this method where all of the floor slabs are cast at ground level one atop the other, then raised as a group and dropped off one by one. In February 1986, lift slab was described as "a basic method of economic concrete construction, especially for structures characterized by repetitive framing from floor to floor." But then, on April 23, 1987, as the slabs were being lifted during lifting of the slabs for construction of the L'Ambiance Plaza in Bridgeport, Conn., the structure collapsed, with the slabs pan-caking to the ground, killing 28 workers and seriously injuring 16 more. Although the exact cause is still argued and despite the economy of lift slab, OSHA restrictions and general uncertainty led to virtual abandonment of the technique.--Bill Palmer

Self-consolidating Concrete

Self-consolidating concrete (SCC) was developed in Japan during the late 1980s. As its name implies, it does not require any external compaction for consolidation. In its fresh state, SCC readily can flow through restricted spaces under its own weight without segregation. These properties are achieved through adequate mix proportioning and addition of superplasticizers. A viscosity-modifying agent or increasing the fines content provides the segregation resistance.

One major advantage of SCC is the ease of casting complicated shapes or densely reinforced structures. Generally, SCC has a better surface finish and requires less cosmetic retouching. Reductions in workforce, casting time, energy requirements, and equipment result in placement cost savings. In addition, the environment benefits from lower noise levels due to the elimination of mechanical vibration.

In North America, SCC usage has been spearheaded by the precast industry, while progress in the ready-mix industry has been slow due to concerns about quality control and formwork pressure. While SCC is well suited for both vertical and horizontal components, extra precautions should be taken to ensure adequate formwork support when casting vertical components. Progress has occurred in standardizing test procedures, but much work is still needed to develop a generalized mix design approach.--Surendra Shah

Post-tensioned Concrete

The first U.S. use of post-tensioned concrete was on the Walnut Lane Bridge in Philadelphia in 1949 with precast post-tensioned girders The first post-tensioning in buildings was in the late 1950s in lift-slab construction. Engineers with lift-slab companies were aware that post-tensioning could control deflection and reduce slab thickness. Once the lifting companies started post-tensioning their slabs, the deflection problems virtually disappeared. The liftslab guys were clever and packaged the tendons into their bids for lift-slab construction, effectively shutting out independent post-tensioning companies. But the result was that this encouraged aggressive post-tensioning firms to develop and submit alternate bids for cast-in-place floors, competing directly with lift-slab. The post-tensioning companies formed an alliance with companies that were developing large-panel flying forms. It turned out that post-tensioned cast-in-place slabs formed with large panel flying form systems were highly competitive with lift slab buildings, and by the late 1960s became the preferred method for multistory slab buildings.

In the early days everyone was using button-headed tendon systems in cast-in-place buildings. The button headed system was replaced by tendons using seven-wire prestressing strand and wedge anchors. The strand system was much more economical than the button-headed tendon system and eliminated all of its major construction drawbacks. Virtually all post-tensioned tendons sold in America for building construction today are strand tendons.

When the earliest post-tensioned buildings were about 15 years old, tendon corrosion problems started to surface, and we realized that some tendon sheathings and coatings could not adequately resist corrosion. Improvements in sheathing and coatings, based on material specifications developed by PTI in the mid-1970s, have largely solved the corrosion problems.--Kenneth B. Bondy

PROJECTS THROUGH THE YEARS University of California at San Diego, 1970

The university's central library, designed by architect William Pereira and built by Nielsen Construction, San Diego, required sophisticated forming because of the overhanging levels. The 17,000 cubic yards of concrete took 475,000 board feet of lumber and uses 2100 tons of rebar. Much of the exterior concrete was placed in forms of rough-sawn lumber to achieve a wood-grain effect.

PEOPLE WHO CHANGED US Bertrand Goldberg

Once called Chicago's great poet of urban architecture, Bertrand Goldberg stretched the limits of what could be done with concrete. Critics labeled him utopian; admirers praised him as an inventor concerned with both the technology of building and its impact on man. But the buildings themselves speak of Goldberg's achievements more eloquently than any critic or admirer. Chicago's Marina City and River City are the prime examples. Born in Chicago in 1913, Goldberg studied at the Bauhaus under Mies van der Rohe but broke from the utilitarian Bauhaus dogma when he designed Marina City in 1959. "I came to the shape of buildings first," said Goldberg. "My interest was in developing a more efficient and lower cost structure. I came to the realization that in these days building a box would not yield the repetition that we were seeking. When I got to the shapes that would yield me the uniformity of dimension and engineering, then those shapes were more readily produced in concrete."

Concrete Pumps

In the early 1960s small line pumps came out of the grout and plaster business. These small pumps had only 3-inch lines, which would not pass standard concrete mixes. The equipment barely got by and had no safety margins on hydraulics or mechanical parts. Therefore dependability was poor, and they were limited to smaller projects.

In the middle 1960s a stiff boom was developed followed shortly by the articulated boom, which allowed starting out on the deck and reaching all the way back to the unit without moving the vehicle. For many years, 3-section booms were common; now 4-and 5-section booms are the norm.

In the early 1970s concrete pumps from Europe included heavy-duty hydraulics, developed for hydraulic backhoes. They could withstand very high pressure and sustain long periods of pumping without overheating. This made higher production possible and represents one of the most important changes in the past 50 years. With the advent of the roll-and-fold boom, 4-and 5-inch lines allowed harsher and tougher mixes to be pumped. Now 5-inch lines are standard with booms.

As pumps continued to grow with booms that reach more than 60 meters, they lent themselves to bigger projects. Big trailer pumps deliver concrete up to 70 or 80 floors and have pumped over 1000 feet in the air. It is common for trailer pumps to deliver 60 yards per hour in front of the finishers for a 30-to 40-floor building.--Bob Weatherton

PROJECTS THROUGH THE YEARS CN Tower, Toronto, 1975

At 1805 feet tall, the CN Tower was the world's tallest freestanding structure. The lower 1500 feet were slipformed and required careful control of concrete strength during winter construction. Peter Smith and John Bickley developed a system to assure that the concrete gained sufficient strength with heated concrete, insulation for 37 feet below the slipform, and one of the earliest uses of maturity methods to monitor strength gain.

ACI Certification-Improving Quality

In 1956, when cylinders were made on a jobsite, or air or slump was tested, the testing technician may or may not have known what he was doing. Too often, he did not, and the test results were likely to be unrepresentative of the concrete--sometimes leading to rejection of concrete that in reality met specifications. While poor testing can still occur, there is more protection when the testing technician is certified by the American Concrete Institute. ACI's Field Testing Technician certification program started in 1983. Once that program was written into ASTM C 94 in 1985 as a requirement for ready-mixed concrete, the program took off and hasn't looked back. In the meantime, other ACI certification programs were started, for flatwork finishers, lab technicians, construction inspectors, tilt-up supervisors, and shotcrete nozzlemen. An advanced flatwork finisher certification is currently being finalized that will certify finishers' knowledge of high tolerance floors. ACI has graded over 250,000 examinations in the past 25 years, and the program has been run in countries from Chile to Mongolia.--Bill Palmer

Decorative Concrete at the Crossroads

I got started in the decorative concrete industry in the early 1980s. In the past 25 years, this subset of the much larger concrete industry has been growing--recently exponentially. As decorative concrete contractors have become more and more technically sophisticated, decorative concrete has become the sexy face of the industry. Both cement manufacturers and ready-mix producers have recognized this and jumped on the decorative bandwagon. The benefit is a potentially more profitable concrete. And the ultimate customers, the general public, are all for it.

Recently, though, the public seems more and more interested in honesty--concrete for concrete's sake. Appreciation of concrete for its form and visual weight, for its interesting and often serendipitous quirks of color and texture, has increased. I think that the concrete industry and decorative concrete contractors are at a crossroads. They should look and listen to their customers and recognize the true values. Concrete does have many benefits, and it can look like lots of great things, but just because it can, doesn't mean it should. Decorative concrete contractors should temper technical sophistication with sensitivity and design sophistication. The concrete industry should be providing concrete that is application appropriate, as visually honest as possible, and is in no way superfluous.--Michael Miller

PEOPLE WHO CHANGED US George F. Leyh

No discussion of the concrete industry in the United States can be complete without the American Concrete Institute. ACI maintains near-total rule over the technical information on concrete and has for its entire 100-year history. Over the past 50 years, no single person has dominated ACI more than its executive director from 1975 to 1998, George Leyh. Having worked for him for nearly 10 of those years, I saw his tireless and even ferocious efforts to maintain the public's and the industry's trust in the Institute and in the information developed by its members. This effort to maintain trust included bringing together the many disparate factions of the industry. He founded what has come to be called CAMRA, the Concrete and Masonry Related Associations, to foster industry-wide projects and collaboration.--Bill Palmer

PROJECTS THROUGH THE YEARS Sunshine Skyway Bridge, Tampa Bay, 1987

At its opening the Sunshine Skyway was hailed by the St. Petersburg Times as a triumph of function and beauty. "For decades to come, the new Skyway will bring tourists out of their way to see it, to ride on it. Tampa Bay will be known by it." Stretching 4.18 miles, the 1200-foot main span is supported by two pylons reaching 431 feet above the water. Designed by Figg & Muller Engineers, Tallahassee, the bridge was built using precast segmental sections that weighed from 150 to 220 tons each--at the time, the heaviest match-cast segments ever placed.

Diamond Tool Impact on the Concrete Market

Cutting concrete with diamond tools began in North America in the late 1940s when flat saws were used experimentally to saw highway joints. Since those early days, many advances in diamond tools and machines allow superior performance, resulting in a dramatic expansion of the market. One of the first leaps in technology occurred in the early 1960s when natural diamonds were replaced with synthetically grown diamonds. This allowed tailor-made crystals in a wide variety of qualities, shapes, and sizes. Today synthetic diamonds have replaced natural diamonds in virtually all construction applications.

Development of synthetic diamonds and higher performance machines necessitated a corresponding advancement in the production of diamond saw blades, core drills, and diamond wire. Diamonds are held in place by a segment or bead, a specially formulated mixture of metal bond powders and diamond pressed and heated in a sintering press. Machines to produce segments and beads have advanced tremendously, allowing longer life and faster cutting. In addition, the technology to attach segments to blades has advanced with laser welding to provide stronger bonds allowing increased performance and lower cost diamond tools.--Pat O'Brien

Concrete Construction on Fast Forward

The concrete industry's response to society's need for immediate gratification is concrete that can be put into service early--in less than a day in some cases! To meet this demand, cement producers have adjusted the composition and fineness of the cement, concrete producers have lowered the w/c, precasters have raised curing temperature, and concrete contractors have taken on fast-track building, bridge, and pavement contracts. In these and other ways concrete has shown itself to be up to the challenge, and high early strength is an option almost anywhere there is an owner who is willing to pay for it. But is there a downside?

One common side effect is that whenever the mixture is modified or the construction procedures configured to increase the early-age rate of strength gain, there is a reduction in later-age strength. "Slow and steady" hydration is portland cement's preference for optimal performance, as long as you have the time to wait for it.

Another aspect of this is that even though strength gain may be accelerated effectively, associated properties such as abrasion resistance, frost resistance, or resistance to corrosion may not be equally accelerated. Thus a structure can be put into service without its full complement of environmental protection. If we are going to pay the price and deal with the side effects of accelerated concrete performance, let's make sure that it matters in the context of the overall project schedule. Does the owner get an equivalent concrete earlier, or an inferior concrete earlier?--Ken Hover

PROJECTS THROUGH THE YEARS Viaduc de Millau.

The 1.5-mile-long bridge near the town of Millau in southern France, consisting of eight spans, sits atop the world's tallest reinforced concrete piers ranging from 260 to 804 feet tall. The complicated formwork of the piers had to be capable of handling high-speed concreting with pressures up to 2100 psf while providing smooth surfaces and sharp corners.

PEOPLE WHO CHANGED US Eugene C. Figg Jr., P.E.

When one thinks of the great bridges of the past 50 years, the first name that springs to mind is Figg. Gene Figg was the father of concrete segmental bridges in America and a pioneer in the development of cost competitive bridge technology. Bridges designed by his firm have become landmarks across America. Figg led the creation of many of the nation's most recognized bridges, including those with record-setting span lengths and first-of-a-kind innovations. Three bridges designed by the firm have received the Presidential Award through the National Endowment for the Arts: the Bob Graham Sunshine Skyway Bridge over Tampa Bay, the Blue Ridge Parkway Viaduct around Grandfather Mountain, N.C.; and the Natchez Trace Parkway Arches near Nashville, Tenn.

Has Concrete Repair Work Changed in 50 Years?

When Zera Construction began in 1957, a cubic yard of concrete cost approximately $12; today a basic mix is $70 to $80. In 1980, when Zera Construction started structural concrete repair work, means and methods were in their infancy. Epoxies and various bagged products were specified in lieu of ready-mixed concrete. Specifiers seemed to believe that the more exotic the material used, the better the result. But that was not the case, and many of these repairs failed in a very short time. Now, there has been a return to reliable, simple concrete mixes with w/c ratios of 0.40 and superplasticizers to improve workability and consolidation.

We've seen a return to the basics with bonding agents, too. Epoxies and latexes were used exclusively for many years to bond patch materials. Today, we find that a mix of sand, cement, and water grout brushed into the area to receive the repair material works best. Much has changed since our company began fifty years ago, and yet some of the basics still stand us in good stead.--Alex Zera

PEOPLE WHO CHANGED US Allen Face

Fifty years ago, no one placed much emphasis on the subjective subject of flat floors. So much has changed in that time with regard to floor flatness and much of that is due to Allen Face. In the late 1970s, Allen worked through the heavy mathematics to come up with a way not only to accurately describe how flat a floor is, but also to definitively measure it. F numbers, as they are now called, were measured by the Dipstick, which was manufactured in 1982 by the family business, run by Allen, his father Sam, and his brother Brad. The Dipstick Floor Profiler is a simple-looking tool that allows contractors to verify the floor flatness almost immediately. The onboard computer measures the elevation differences between the two ends of the unit as you walk it across the floor. Allen went on to become the industry's leading expert on floor flatness, creating the F-Meter Rolling F-number tester, the Slab Sentinel, and other tools to measure slab characteristics.

The Laser Revolution

When laser technology was first developed in 1960, manufacturers scrambled to discover practical uses. The first grade laser, using an electronically oscillated transit, was workable in the 1960s. The first adjustable machine control and rod mounted laser receivers appeared at the same time. Self-leveling lasers followed by 1973.

The 1980s saw numerous developments as machine control became more refined and specific systems for specific machines became the norm. Road graders were controlled with a sonic sensor to provide height and line control simultaneously. The first visible laser diode took over the prominence of the helium-neon tube as it offered lower pricing and a self-contained power supply.

The 1990s began a wave of technology that dramatically downsized the equipment. Laser models began the transition to onboard power. This technology pioneered the first handheld laser distance meter. Measured data transferred wirelessly to a PDA or directly to a laptop.

At the turn of the century, the laser revolution continued to spread. Increased production, greater accuracy, and lower material costs have been the benefits. The inherent precision of lasers has made a tremendous impact on all involved in concrete construction.--John Schultz

Insulating Concrete Forms

When ICF foam forms were first created in the mid-1960s, few could have imagined the impact they would have on the construction industry. With high energy costs, frequent natural disasters, anti-terrorism issues, and overall speed and cost of construction-all impacting home and building owners--it is no wonder ICF use has grown so dramatically.

After ICFs were introduced as a lightweight replacement for heavy steel pan and plywood concrete forming systems, home builders soon wanted to use them to form foundations and eliminate subcontractors, control their construction schedules, and take profit back to their bottom line. Something interesting happened, though. Because of the energy-efficient properties and ability to shield homeowners from loud outdoor noise, homeowners began preferring the comfort and quiet of their ICF basements to the first and second floor, stick-framed areas of their homes.

With skilled labor in high demand, commercial contractors also began using ICFs to speed up construction without the learning curve associated with more complicated building systems. Architects, engineers, and building owners searched out ICFs to address long-term issues like durability, low maintenance, and energy efficiency. Although ICFs represent only a small portion of the overall construction market, the increased use is impressive. Over the past five years, ICF use in the residential market has increased 73%. The growth in the commercial market is even more impressive, 172% in the same period.--Joe Lyman

PEOPLE WHO CHANGED US David Somero

It all started in 1983 when David Somero s concrete construction company joined forces with another contractor to install a 300,000-square-foot floor--considered a huge floor at the time. David was bothered by the hardware and rails required to guide conventional concrete screeds. So he and his brother Paul began questioning how existing equipment and technology could be modified to do what they had in mind. Conversations with manufacturers followed, but by 1985 they decided to build their own machine. From the beginning, Spectra Physics (now Trimble) was involved with their laser guidance equipment. The only problem was that they couldn't get anyone to buy it. They brought their invention to jobsites and the World of Concrete, offering to let contractors try it for a day at no charge. By the end of the 1980s there were still only a few machines in operation. As the recession came to an end in the mid-1990s though, things took off and their factory started producing one machine a day. With the invention of the Laser Screed, David Somero changed the way we place concrete for floor construction and has saved many a concrete finisher's back--not to mention greatly increasing the quality of concrete floors.

Roller-Compacted Concrete Pavements

Roller-compacted concrete (RCC)is a zero-slump concrete that is compacted by vibratory rollers. The use of RCC for pavements evolved from the use of soil cement and cement-treated base (CTB) material. Although equipment for batching, mixing, and transporting roller compacted concrete is similar to CTB, RCC is designed to have a much higher strength and durability.

According to the U.S. Corps of Engineers, the first use of RCC pavement in North America was a runway at Yakima, Wash., constructed in 1942. The Corps installed the first known RCC test pavement at Vicksburg, Miss. in 1975. This 300-foot service road proved the feasibility of RCC for use in pavement construction.

In general, RCC has been used for heavy-duty pavements, such as yards and port facilities. However, in the past 10 years RCC has also been proven to be a cost-effective pavement for many conventional pavement applications including warehouse facilities, industrial access roads, large commercial parking areas, intersection replacements, roadway inlays, highway shoulders and residential streets. Some of the changes that have occurred since the early projects include use of heavy-duty asphalt pavers to improve initial compaction and enhance surface texture and smoothness.--Wayne Adaska

Awareness of Concrete's Sustainability Grows

While our industry has made many advances over the past five decades, we now see the birth of a movement that will affect the perception and use of concrete in the future. Rising energy costs, limited resources, health concerns, and dramatic weather have led to a growing awareness of the impact humankind has on this planet. The concrete industry has a responsibility to make a positive difference for sustainable development.

The design community has a huge task--understanding and integrating the impacts of the built environment on the natural environment. It must comparatively evaluate the manufacturing process, shipping, construction, maintenance, and deconstruction for all materials that go into a project, and they are looking to us, the concrete experts, for answers.

Concrete's greenest benefits are derived from its strength, durability, and recyclability. Architects routinely note durability as a reason for using concrete. It is truly sustainable: does not burn, rot, rust, warp, off-gas, or provide food to mold and insects. Today's concrete solutions improve the air and water quality on building sites, save energy over traditional building methods, and reduce urban heat islands. When reaching the end of its original life, concrete can be recycled for use in roads, utilities, and new building construction.

But sustainable development is not simply about stacking a bunch of green products onto a foundation. Research clearly shows that the impact of materials alone is a small fraction, when considering the life span of the structure. It is design of the building and considerate integration of the materials that makes large improvement possible.--David Shepherd

Fifty Years of Shotcrete Progress

Shotcrete has been around for 100 years. While the early gunite, or dry-process shotcrete, grew in use and various applications around the world for shotcrete's first 50 years, it was in the second 50 years that great progress was made in three important areas.

First, the introduction of the rotary gun in 1957 allowed higher production rates and larger aggregate mixtures to be used in the dry-process, opening up new applications and increased flexibility in mixture proportioning. In the 1970s the development of practical concrete pumping equipment spurred the growth of the wet-process shotcrete application.

Second, the American Concrete Institute established Committee 506 on Shotcreting in 1942 for the purpose of producing shotcrete specifications and other documents on the practical use of the shotcrete method. In 1990, ASTM established Subcommittee C09.46 on Shotcrete to develop material specifications and test methods for shotcrete.

Finally, the development of a Nozzleman Certification program by ACI in 2001, with support from the American Shotcrete Association, allowed the industry to comply with existing specifications while increasing the technical knowledge and ability of nozzle operators throughout the world. By combining further advances in equipment, concrete technology, and operator proficiency, the shotcrete industry will continue to make significant advances in its second century.--George D. Yoggy and Peter C. Tatnall

Skid-steer Loader Mechanizes Manual Labor

The skid-steer loader started out as a three-wheeled machine made by Melroe Manufacturing Co. It featured two drive wheels and a rear caster wheel, with lift arms and a simple utility fork attachment up front. This quick, agile loader replaced a pitchfork and a strong back to save hours of hard labor on farms and in areas too small for conventional machines.

That was soon followed by development of the four-wheel-drive skid-steer loader--similar to the thousands seen on jobsites across the country. Dubbed the "Bobcat," the concept proved so popular that the company ultimately changed its name to the Bobcat Co. Within a short time, equipment manufacturers were making dozens of versions of the skid-steer loader. The machine can also be credited with creating the compact equipment market that includes an exhaustive range of categories, including compact excavators and mini backhoes.

The skid-steer loader also led to a demand for attachments. Standard attachments now include augers, box blades, brooms, breakers, drop hammers, and buckets. The evolution of this versatile machine has been toward ever increasing sophistication.--Ryan Johnson

Advances in Drilling

A star drive and hammer were the tools of choice for concrete contractors 50 years ago, not exactly the most sophisticated or productive system (drilling a simple anchor hole could take more than 90 minutes, but an essential system because it was the only technology then available. About ten years later, Hilti, still in its early days as a building and construction product manufacturer, introduced a tool that dramatically changed concrete construction forever. With the electropneumatic hammer drill, the time needed to drill an anchor hole was shortened to about one minute. In the 1990s, vibration reduction systems were developed for hammer drills that are easier on the hands and arms so they are less tiring to use, increasing productivity.--Renee Robinson

PEOPLE WHO CHANGED US Dave and Phil Arnold, L.M. Scofield Company

In 1915, Lynn Mason Scofield, an engineer and inventor, introduced the first successful products for permanently coloring, staining, and protecting concrete. Scofield's headquarters moved to Los Angeles during the era when trend-setting California architects favored Art Nouveau and Art Deco, ideal for Scofield's reactive, penetrating stain. In 1938, Lynn's son, George Scofield, a chemist, took over leadership. He brought a system approach and started the training program that is now called the Scofield Institute. The Arnold family acquired the company in 1962, led by David R. Arnold. In 1994, his son Phillip J. Arnold, an engineering graduate of Caltech who holds a Stanford MBA, assumed the leadership of Scofield.

"In retrospect," says Phil Arnold, "as we celebrated our 90th anniversary and looked at our long-term involvement in the concrete industry, several important topics came into sharp focus. First, training and standards continue to be vital to the success of the industry and to attracting and retaining the workforce that will enable quality work and continued growth. Second, communication is the backbone of our relationship with contractors and distributors. Third, we expect increasing demand for aesthetically attractive architectural concrete, with its extraordinary versatility to answer many of the concerns facing the construction industry today."