Concrete Construction drew its first breath in the midst of an industry that was enjoying explosive post-WWII market growth and technological innovation. The days of portable onsite mixers and slow placement methods were slipping away. Ready-mixed concrete was becoming ubiquitous, delivering large batches that had to be placed promptly. This, in turn, drove advancements such as pumps, conveyors, power vibrators, screeds, and troweling machines, all designed to allow placing and finishing concrete at high rates.
Ready Mix in '56
By the time Concrete Construction debuted, the National Ready Mixed Concrete Association had already celebrated its Silver Anniversary. Some 2000 ready-mix plants were doing a combined $1 billion worth of business, selling concrete at about $13 per cubic yard. Touted as one of construction's fastest growing segments, the ready mix industry was riding the post-war boom.
Still, the industry was relatively new. Ready mix had not yet been added to the Wholesale Price Index. Making inroads into the site-mixed concrete market had been an uphill battle, and there were naysayers. In the March 1957 issue, after a half year of publication, the editor felt it necessary to respond to readers “demanding to know if it is our mission in life to function as an apologist for the ready-mixed concrete industry.” And in 1959 an article exploring the suitability of truck-mixed concrete for pavements said the matter “has long been a subject of debate among contractors and people responsible for the quality of pavements.” This was a critical issue, considering the new Federal Highway Act had just authorized 41,000 miles of concrete interstate.
Pumping: Booms a Boon
One of the concrete industry's most significant developments in the past half century was the truck-mounted boom pump, introduced in the 1960s. Concrete Construction followed the booming market with this blow-by-blow coverage:
1968 Pumping is currently the fastest growing method of handling concrete. Concrete can be pumped up to 200 feet vertically.
1971 In little more than five years, the pumping of concrete has been jet propelled from relatively crude pioneer beginnings into a sophisticated construction practice respected for its ability to telescope both pumping distance and time. The pumps, the carriers, the lines, and booms are proliferating in number, power, and capacity.
1974 The Portland Cement Association reported that 20 million cubic yards of concrete were pumped in 1971, 10% of the total produced, and predicted that 50% of all concrete would be pumped in 1980.
1980 Concrete pumping in the United States took a sizeable leap upward recently when concrete was pumped 729 feet vertically to place the last of 50 floors in the Capital National Bank Plaza in Houston.
1982 In the construction of the 75-story Texas Commerce Tower, Houston, a single concrete pump at ground level pumped lightweight and hardrock concrete vertically 1030 feet.
2004 Pumps have been used to place concrete as high as 1460 feet for a floor slab on the Taipei 101 tower, the world's new tallest building. One long-sought-after pump innovation is a true telescoping boom. Recently, we heard rumors of a truly telescopic boom section being manufactured; it's too early to say whether this works or not.
Conveyors Can Do
Although the use of conveyors to place concrete has been documented as early as 1932, early attempts to adapt existing industrial conveyors for concrete met with mixed success. As a result, the concept didn't immediately gain widespread acceptance. By mid-century, however, the move to ready-mixed concrete triggered the need for quick placement. The idea of using conveyors was revisited, and new units were developed specifically for concrete.
Thus, in 1963, the fledgling Concrete Construction touted concrete conveyors as “an important new development.” The magazine hastened to enlighten readers about the three basic conveyor types—portable, feeder, and spreader—and over the years has kept pace with the myriad variations and combinations of this versatile tool.