Q: We've been asked by a design-build firm to submit a mix design on an upcoming project that may be considered for LEED accreditation. One portion of this project features a large parking structure. This is a unique project in that the design-build firm has been asked to review each option by estimating the service life of the structure. The firm is considering other materials as well as reinforced concrete.
We seem to be facing a double-edged sword in this opportunity. First, we must develop a cost-effective mix design that will enable us to be competitive with other materials, especially steel. And we must then be able to provide verification that the structure will meet or exceed the project's design life requirements.
Is there an effective tool to help us prepare this project submission?
A: In the last few years, researchers have made great advances in creating models that can predict the service life of reinforced concrete in structures. These advances have led to the recently issued Version 2.0.1 of Life-365. Life-365 is software designed to estimate the service life and life-cycle costs of alternative concrete mix designs.
Engineers and architects using The Model for Predicting Service Life and Life Cycle Costs of Steel-Reinforced Concrete Structures can compare different strategies and techniques to help them choose the best option. The software follows a methodology, created by the Life-365 Consortium I and II groups of companies, that gives research-based estimates of the effects of concrete design, chloride exposure, environmental temperature, concrete mixes and barriers, and steel types on service life and life-cycle cost.
While the model has been available to the public for more than a decade, Version 2.0.1 has a feature that makes it more producer-friendly than previous versions. This version's software now incorporates a special default feature that allows a producer's quality control engineer to override the model's general value set and input producer-proprietary, regional, or project-related material data.
This model is especially useful for bridge decks and parking structures. These structure types can be exposed to very corrosive conditions. The model provides a wide selection of strategies. Users can choose to mitigate corrosion-induced damage by considering options such as high performance concrete with low permeability qualities, corrosion inhibiting admixtures, epoxy coated steel reinforcement, waterproofing membranes, or sealants.
The new version of the software also features seven video presentations that help users navigate through the model building process.
Members of the consortium supporting this newest software development include the Cement Slag Association, the Concrete Inhibitors Association, the National Ready Mixed Concrete Association, and the Silica Fume Association. To view the model, visit www.life-365.org.
Measuring SCC segregation resistance
A new ASTM standard provides a field test to measure self-consolidating concrete's stability. C1712, Test Method for Rapid Assessment of Static Segregation Resistance of Self-Consolidating Concrete Using Penetration Test provides results within minutes of production or placement. According to Mark Bury, product manager, BASF Corp., Admixture Division and chair of C09.47, the new test correlates well with other lab-based procedures that measure mix stability. “Producers can adjust mixes on the go with confidence using this method,” says Bury.
To purchase the standard, visit www.astm.org and search by standard number.