Title: Examination and Evaluation of ACI 347.3R-13 "Guide to Formed Concrete Surfaces"

Author(s): Ward R. Malisch; Heather J. Brown

Publication: CRC

Volume:

Issue:

Appears on pages(s):

Keywords: Guide to Formed Concrete Surfaces, 347.3R-13-13, formed concrete, surfaces

DOI:

Date: 4/14/2017

Abstract:
After ACI 347.3R-13-13, “Guide to Formed Concrete Surfaces,” was published in early 2014, a study was funded to evaluate and examine the Guide. A summary is provided below. • In a review of ACI 347.3R-13 similar to an ACI document review, the investigators expressed concerns about the mixture of objective and subjective criteria for categorizing formed surfaces, mandatory language used in the Guide, and vague or undefined words or phrases. Complexity and achievability of recommendations in the Guide were also questioned. Chapters 2 through 4 of this report summarize results of the review and Appendix B contains the full review. • A literature review of information on bugholes—as measured by the surface void ratio (SVR) recommendations in the Guide—provided background information on SVR recommendations, other criteria for assessing and classifying surface appearance, optoelectronic image analysis for measuring SVR, factors affecting the size and frequency of bugholes, and methods for controlling the factors. Results of the review are summarized in Chapter 5 of this report, and Appendix C is an annotated bibliography of the literature reviewed. • Student researchers in the Middle Tennessee State University (MTSU) Concrete Industry Management (CIM) program made SVR measurements on photos of walls with varied sizes and numbers of bugholes while testing several methods of measurement including the method described in the ACI Guide. They chose three measurement methods for further study on as-built vertical concrete as described in Chapter 6 of this report. • The MTSU student researchers next built a wall for use in testing different SVR measuring methods and estimating the variability among 2-ft by 2-ft samples randomly chosen on the wall. There were wide variations in SVR for sample-to-sample testing and within-sample testing on the test wall. The data collected enabled development of SVR sampling and measurement protocols for use by student researchers from three other CIM schools. • Students from the other three CIM schools made SVR measurements, first on photos to develop reproducibility data, then on in-place walls in their geographic area. MTSU CIM students also made SVR measurements on in-place walls in Tennessee. • Data from the CIM student researchers was supplemented by data obtained from three U.S. commercial testing laboratories. • Wide variations in SVR for sample-to-sample testing and within-sample testing were again evident. Based on convergence of the running average for multiple measurements, about six to nine samples were needed for the MTSU test wall with an average SVR of about 3%. Need for a similar number of samples was indicated by testing laboratory results on a wall with an average SVR of about 0.4%. • On a trip to Germany, the principal investigator found that evaluation of SVR on an as-built wall is based on one “representative” sample chosen by the general contractor. • Results from measurements made by CIM student researchers and testing laboratories indicate that, based on one sample, measurement and sampling error can produce SVRs for a given wall placing it in the worst to best category. • The literature review produced little evidence that producers’ or contractors’ methods for concrete production or construction can be modified to consistently produce a given SVR due to the number of variables involved. • This report recommends that requirements for both color, which is subjective, and SVR, which appears to be objective but is subject to sampling and measurement error, be omitted from any recommendations for formed vertical surface appearance. This report recommends not including ACI 347.3R-13 as part of a bid package and not converting it to a specification.