It's going to be quite a week for the ACI Tolerances committee as March turns into April this year. To begin with, Colin Milberg and his team from San Diego State University (SDSU) will have their laser scanning setup on display as one of the exhibits at the ACI Convention in Los Angeles. The exhibits open on Sunday, March 30, and go through Wednesday morning. SDSU students who are involved in the data collection project will be manning the booth throughout that time, so if you're attending the convention, take a moment to stop by and see the scanner in action.
Then on Tuesday, April 1 at 8 a.m. the committee will meet to continue work on its three large ongoing projects. Revisions currently are being considered to ACI 117, “Specifications for Tolerances for Concrete Construction and Materials and Commentary.” As part of the effort to include items addressed in ACI 301, “Specifications for Structural Concrete,” and to get the 117 document onto the same cycle as ACI 301, these revisions include addressing architectural concrete and the addition of sections on tilt-up construction and concrete interfaces with precast elements.
Also new in this revision will be a reference to tolerances for precast concrete, which are being brought in through an Innovation Task Group (ITG). This process, which is a relatively new mechanism within ACI, uses a smaller group of people to develop a standard or report focused on a very specific item. In this case, the group is charged with producing ITG-7, “Specification for Tolerance for Precast Concrete.” It is based on PCI tolerances currently used as standard practice within the industry, but which are not incorporated into a standard. ITG-7 will go through the complete ANSI approved standardization process so that it can be referenced by other ACI documents.
In addition, the project spearheaded by David Ballast—a new document titled “Guide for Tolerance Compatibility in Concrete Construction” (see September 2007 Tolerances column)—is on the docket for consideration. The first draft of this document is being balloted within the committee and will be further discussed in Los Angeles. Ballast reports the guide will include information on how to deal with compatibility concerns in various areas of construction and also includes a wealth of illustrations and commentary.
One other item will be a progress update on the “Standard Measuring Protocol for Evaluation of Concrete Elements for Conformance to Specified Tolerances,” which Milberg is heading up (see July 2007 Tolerances column). Based on field data collection efforts using sophisticated laser scanning equipment, this project is focused on developing realistic and achievable tolerances for many different aspects of concrete construction.
As a bit of a preview, Milberg told me he is realizing how difficult the coordination is going to be for some of the data collection efforts. His initial field scans collected information on vertical elements—walls and columns—but recently he scanned a slab in Los Angeles, his first onsite scan of horizontal elements.
What surprised him was how quickly equipment and materials are placed on the new slab, typically within 24 hours. Although technicians can work around such obstructions in scanning walls and columns, the ability to scan the surface disappears once these items are placed on a slab. “The window of opportunity to get data on the top surface is going to be very tight,” he says. For more details, join Milberg at the committee meeting.
As if the exhibit and the committee meeting weren't enough, be sure to put the Tuesday afternoon Contractor's Day panel discussion “Know Before You Build—Part 2” on your convention schedule. ACI 117 committee chair Eldon Tipping will be on the panel, as well as Milberg and Ballast. Other panelists include Allen Face, of The Allen Face Companies, Wilmington, N.C., and Jim Tkach, a senior project manager with Morley Construction, Santa Monica, Calif.
Although the panel's full agenda is still in preparation, topics are expected to include the current state of tolerance documents, ongoing research and measurements, coordination with materials adjoining concrete, and perhaps a demonstration of some of the measuring devices being used. The goal is to provide an overview of what's happening in the industry, and to have interaction with those in attendance.