THE CONCRETE BRIDGE MAGAZINE

Summer 2019

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/1134112

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capabilities and expertise, and helps the firm to attain access to potential clients in California, where Twining is based. "We had been courted in the past as a potential partner, but we never considered such offers seriously until we began a conversation with Twining," Rothstein says. "They continually push at the forefront of the industry, refining existing strengths and services, and developing new capabilities and expertise. This is exactly the kind of organization that we want to align with." The potential for growth as new challenges arise keeps DRP engaged and looking to the future. "We're always finding new ideas and stumbling upon new anomalies that need to be examined and understood," Rothstein says. "The industry continues to create new aggregates, new mix designs, new admixtures, and new questions we need to answer. That's what keeps it fun." 'We're always finding new ideas and stumbling upon new anomalies that need to be examined and understood.' References 1. Spragg, R.P. 2017. "Development of Concrete Performance Specifications that Include Formation Factor." PhD dissertation, Purdue University, West Lafayette, IN. 2. Weiss, W.J., R.P. Spragg, O.B. Isgor, M.T. Ley, and T. Van Dam. 2 0 1 7 . " To w a rd P e r f o r m a n c e Specifications for Concrete: Linking Resistivity, RCPT and Diffusion Predictions Using the Formation Factor for Use in Specifications," In: Proceedings. fib Symposium 2017, International Federation for Structural Concrete, Maastricht, The Netherlands. DRP Consulting Inc. (David Rothstein Petrographic Consulting) was founded in 1996 by David Rothstein after he earned a PhD in geology at the University of California, Los Angeles, and was asked to analyze the types of aggregate in a client's quarry. In 1999, he began postdoctoral studies at Northwestern U n i v e r s i t y i n E va n s t o n , I l l . , w h i l e continuing his consulting business. In 2001, Rothstein moved to Boulder, Colo., to work on concrete structures of all types. In 2009, he hired an assistant to handle sample preparation, then an administrative assistant to handle paperwork, and then two more petrographers. Today, the firm employs six people and is a subsidiary of Twining Inc. of Long Beach, Calif. DRP Grows, Evolves 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 0 20 40 60 80 100 120 140 Formation Factor Estimated Years to Corrosion Initiation Low Chloride Surface Concentration (C s = 0.1%) Medium Chloride Surface Concentration (C s = 0.5%) High Chloride Surface Concentration (C s = 1%) An example of the relationship between formation factor and predicted service life. Note: C S = the concentration of chlorides in solutions in contact with concrete. Figure developed from an approach described by Spragg. 1,2 EDITOR'S NOTE See the FHWA article on Performance Engineered Mixtures (PEM) in the Fall 2017 issue of ASPIRE for more discussion of the formation factor and other innovative approaches to ensure a longer service life for concrete structures. ASPIRE Summer 2019 | 9

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