Concrete Products

JAN 2019

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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68 • January 2019 FEATURE BY DON MARSH TOWERING OPPORTUNITY Before setting its sights on southern Cali- fornia, Polaris Materials garnered an elite customer following in the San Francisco Bay Area, home to Eagle Rock's premier facility, a Port of Richmond terminal permitted for 1 million tons annually. The Port of Long Beach terminal spawned a second Eagle Rock marketing and technical team charged with demonstrating Orca aggregates' potential to advance HPC specifications and practice in the Los Angeles Basin. Team leader Dick Wil- liams joined Polaris Materials and Eagle Rock after 40 years of industry service, including senior and executive management roles in multiple concrete industry segments. One of his later assignments was corporate vice president of Marketing and Sales (2000-2005) for U.S. Concrete Inc., which acquired Polaris Materials in 2017. Through its San Jose-based Central Con- crete Supply Co. business unit, U.S. Concrete had observed since 2007 the potential for Eagle Rock to disrupt San Francisco Bay Area construction and engineering. Management saw a similar story beginning to unfold in Los Angeles, where MOE thresholds rule the day in structural concrete. "By having the superior quality of Orca materials, engineers don't have to just talk about MOE. They can now produce high mod- ulus of elasticity concrete designs in the 4,000-7,000 ksi ranges," says Williams. "That was a discussion no one wanted to have when aggregates typical of the southern California market were yielding concrete with MOE in the 3,800 ksi area at best. Modulus of elas- ticity and other performance attributes have put our sand & gravel on the southern Cal- ifornia map." A June 2017 memo, "Required Concrete Modulus of Elasticity Testing for High-Rise Concrete Buildings," leaves no question where the City of Los Angeles Department of Building and Safety's Permit & Engineering and Inspection Bureau Chiefs stand on struc- tural concrete member stiffness: Concrete high-rise buildings are designed and constructed based on calculated modulus of elasticity (MOE) to confirm compliance with the building drift limits. MOE shall be part of the approval of the concrete mix design for all new concrete buildings with structural height of more than 160 feet. Notes on the structural plans shall specify the MOE for concrete used in the design of the seismic force resisting system, including beams, columns and shear walls … [and] indicate: 'The mix design shall specify aggregate with a modulus of elasticity not less than that specified on the plans. This modulus of elasticity of the aggregate shall be consistent with modulus used in the trial mix designs for establishing the concrete f'c and MOE used in the building design' … MOE of the trial mix design shall be verified through testing in accordance with ACI 318 R8.5.1, referencing ASTM C469 Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression results. The MOE–aggregate link in concrete spec- ifications and structural member dimensions was astutely detailed months before the LA Building Department memo in a report from the industry's foremost HPC producer, Chi- cago-based Prairie Material. In "The High E Trend Continues," Lab Services Manager Nick Beristain cites a project analysis revealing that each 10 percent increase in MOE afforded a potential 10 percent decrease in concrete column sizing. "Even though higher psi is generally indicative of higher modulus, we found that density of the stone has a greater impact on modulus values," he observes. Prairie-branded High-E concrete mixes in structural condi- tions provide high compressive strength, reduced creep and higher stiffness than con- ventional mixes, he adds, while their "greater rigidity helps to control drift and motion in tall buildings." The Long Beach terminal launched with ships from Vancouver island delivering once a month, a frequency since increased as Orca aggregate demand and permitted output have climbed. The terminal boom has a 60-in. belt charging 48-in. main conveyor and stacker belts; target unloading rate for the premium sand & gravel is 2,500 mt/hour. Terminal staff create a small sand stockpile (above) for truck loading on ship days to eliminate interfer- ence with main and radial stacker conveyor operations.

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