Getting up before the sun is a fact of life in the concrete industry, especially in summer. Most producers and contractors can look forward to wrapping up a long day of work when the sun goes down. At Smokey Point Aleutian Concrete in Dutch Harbor, Alaska, that can be after midnight.
The producer has to make every day count between March and October, when workers can expect at least 10 hours of sunlight. But the sun is a minor obstacle compared to other challenges posed by producing concrete in this rugged environment.
With its plant located in the Aleutian Islands, southwest of Alaska's mainland, the producer must import all of its sand, cement, admixtures, and some aggregates by barge. Five full-time employees run four ready-mix trucks in weather ranging from 27° F to 60° F, mostly in cloudy and rainy–and sometimes blizzard–conditions.
Owner Ryan Costanti bought the business with three partners in 2008 after 15 years as a concrete contractor. With this background, he understands that good communication is essential to the success of any project. However, producing concrete for tough, remote jobs demands a whole new level of insight: how to make the right materials for the job.
Designing the right mix
Chemical admixtures are the secret ingredients that allow Smokey Point to specialize in fast-track projects in harsh conditions. “We're not afraid to try new mixes if it means improving the quality of our concrete,” says Costanti.
Recently, the producer provided concrete for an 80,000-square-foot cold storage warehouse slab at Dutch Harbor's Kloosterboer Dock. The time frame was extremely tight, since the freezers had to be cold by the Fourth of July and the contractors, Industrial Resources Inc. from Clear Lake, Wash., would not pour the concrete until a month prior. Smokey Point worked with the project engineer, Anchorage-based R&M Consultants, to design a 6000 psi mix to meet the 4000 psi required in time to turn on the freezers.
The high-performance concrete included accelerators, polycarboxylate mid- and high-range water reducers, and viscosity modifiers. The concrete was air-entrained to increase its durability, since the freezer temperatures reach -20° F. Slabs were designed with reinforcing steel, but the producer saved time and labor by replacing all of the rebar with macrofiber (5 pounds/yard).
After the warehouse slab was finished, Smokey Point supplied ready-mix for a 20,000-square-foot section of the adjacent dock. Again, the producer collaborated with R&M Consultants to design concrete that would withstand the harsh environment. The 7000 psi mix included 35 pounds/yard of silica fume as a densifier to limit the penetration of water during freeze/thaw cycles and salt. The contractors did not apply a coating or sealant, but used a vapor retarder to combat the silica fume's drying effect.
In addition to supporting cargo and heavy machinery, concrete docks in Alaska have to meet Zone 4 seismic requirements (the same as Los Angeles and San Francisco). Kloosterboer Dock required a double mat of rebar and a higher cement content in the concrete. A polycarboxylate high-range water reducer increased the concrete's workability so it could flow more easily into place around the dense steel grid. The mix also included an accelerator and 5 pounds/yard of macrofibers. “Often there are several ways to get the same results,” says Costanti. “We work with the contractor to achieve the required strength as quickly as possible.”
This spring, Smokey Point embarked on a two-year project to deliver concrete for the new Akutan Airport. The 1500-yard project is on an island 70 miles from Dutch Harbor. “We bid the job several different ways, including using a portable plant or taking trucks over on a barge,” says Costanti.
In the end, his most cost-effective option was to batch dry concrete into 1-yard bags, which the contractor will deliver once a week by barge and mix at the jobsite. The high-performance concrete will include polycarboxylate water reducers and accelerators to meet strength and low temperature placing requirements.
Jobs like these test a concrete producer's ingenuity and knowledge of materials. Costanti takes advantage of the resources he has available, such as continued assistance from his company's previous owner, Smokey Point Concrete Inc. based in Arlington, Wash. He also traveled to World of Concrete this year. One reason he made the 4500-mile trip was to attend the Using Chemical Admixtures to Achieve Better Concrete seminar.
Chemically enhanced concrete
The seminar was presented by Bill Phelan, senior vice president of marketing and technical services for Euclid Chemical, and Jack Gibbons, central region manager for the Concrete Reinforcing Steel Institute (CRSI). The presenters gave an overview of admixture types and specific applications. These were illustrated by case studies, including projects such as the tallest building in the world, the Burj Khalifa in Dubai, UAE, Freedom Tower in New York, and Chicago's Trump International Hotel & Tower, the largest concrete high-rise in North America.
Phelan and Gibbons discussed high-performance concrete mixes in which several types of admixtures can be used to meet a job's unique requirements. They stressed “one mix does not do it all,” and that successful concrete projects require optimized mix designs that are tailored to the placing environment and specific hardened properties. Ultimately, they said, chemical admixtures help expand the concrete market by enhancing the performance of all concrete and making high-performance concrete easier to achieve.
As chairman of ACI Committee 212, Chemical Admixtures, for six years, Phelan led an effort to revise the group's Report on Chemical Admixtures for Concrete. The 2010 version (ACI 212.3R-10) features expanded coverage from six to 16 chapters, including 12 categories of admixtures. (See sidebar.) “The new chapters include information that is not generally known, with real project examples to show what is being done with these admixtures,” says Phelan.
Of all of the groundbreaking work with chemical admixtures in recent years, Phelan sees self-consolidating concrete (SCC) as potentially the most significant technology for the industry over the next five to 10 years. With a flow spread of 20 to 30 inches, SCC is a highly flowable, non-segregating concrete that can completely fill forms without mechanical consolidation. This makes it an ideal choice for precast producers, who have been early adopters of the technology in the U.S. SCC is typically made with polycarboxylate-based high-range water reducers, viscosity modifying admixtures, and well-graded aggregates.