Reflecting reality
Given ACI 301 is used around the world, it is available in metric units, and a Spanish version will be published this year. However, ensuring the specification is truly applicable anywhere from Peru to Canada takes more than simple translation.
“ACI 301 is a conservative specification that covers many different applications. There are some restrictive provisions that are intended to provide structural, stable, and durable concrete in service,” says Wilson. “However, there are several contractor-friendly options that ensure we’re not restricting the builder’s ability to decide means and methods.”
In fact, many changes to ACI 301-16 are performance-based to better reflect standard industry practices. Concrete slump, for example, is no longer defined by the specifier. Contractors must choose, to a specific number of inches, the slump best-suited for their given application, then place concrete within the specified slump tolerance.
Previous versions of ACI 301 also included a checklist of submittal items, which was cumbersome for contractors and specifiers to utilize. Submittals are now defined in the body of the specification, so one does not need to jump between the body and a checklist at the back of the document.
Drawing on industry expertise
As a specification rooted in actual jobsite practice, ACI 301-16 reflects the complexity of concrete construction—sometimes there is no straightforward answer.
“We took on several controversial subjects and weren’t always able to reach consensus,” says Jim Cornell, general superintendent at Beck Group (Fort Worth, Texas), and past chair of the ACI 301 Committee.
Cornell says, for example, descriptions of what may qualify as mass concrete in ACI 301-10 were “bulky, non-specific, and open for interpretation.”
After a concerted effort to refine the standard, the committee was unable to reach a better solution. In the end, the cementitious materials content—300 kg/m3 (660 lb/cy)—which had led to much debate, was simply removed.
New to ACI 301-16 are specification provisions addressing alkali-silica reactivity (ASR). ACI Committee 301 expended considerable effort on writing requirements providing for the long-term durability of structures, using the best, most current knowledge of test methods and mechanisms of failure. The committee focused on developing requirements usable across many geographic locations, despite the set of challenges each region presents to providing ASR-resistant materials for concrete. The published specifications provide clear direction for the testing of aggregates, as well as a choice of performance and prescriptive approaches for reducing the risk of ASR.
In other instances, committee members referred to specifications generated by industry associations outside of ACI.
“Certain topics may not have been covered in-depth by ACI 301 or other ACI specifications before, but other industry experts have developed comprehensive mandatory-language reference documents,” says Cornell.
ACI 301-16 now includes external references for topics such as reinforcement and post-tensioned concrete.
The specification refers contractors to a new document from the Concrete Reinforcing Steel Institute (CRSI) to determine proper support for welded wire reinforcement (CRSI RB4.1 [2014], Supports for Reinforcement Used in Concrete, covers the design, use, and material requirements of various reinforcement supports used in concrete. For more information, visit www.crsi.org.), as well as a specification published by the Post Tensioning Institute (PTI) for grouting of bonded tendons. (PTI M55.1-12, Specification for Grouting of Post-Tensioned Structures, provides minimum requirements for the selection, design, and installation of cementitious grouts and ducts for post-tensioning systems used in concrete construction. Additional information can be found at www.post-tensioning.org.)
