Finding ways to define the texture of a concrete surface in a fair and objective way is a worthy goal since contractors are often required to provide surfaces that are poorly specified. Towards that end, almost two years ago, the American Concrete Institute released ACI 347.3R-13, Guide to Formed Concrete Surfaces. We recognized that work in January 2015 by naming Rolf Spahr as one of the Most Influential People in the Industry.
But concern soon arose over the “recommendations” (since 347.3 is a guide, it can only make recommendations, although the new version of ACI SP-4, Formwork for Concrete, seems to encourage specifiers to turn these recommendations into mandatory specification requirements). The technical staff of the American Society of Concrete Contractors felt that parts of the guide lacked clarity, were confusing, and were unachievable using common U.S. forming methods. If specified, this guide could actually be putting contractors at greater risk of rejection of wall panels.
This concern led to a research project, reviewed by Ward Malisch during the September ASCC Annual Meeting, to identify “complex or confusing requirements” in the guide. That was followed up by hands-on research by Concrete Industry Management students at Middle Tennessee State University to attempt to measure the “surface void ratio”, or bugholes in a concrete surface, which proved to be difficult and highly variable—different observers easily came up with very different results.
The work continues in an effort to find ways to fairly define achievable surface textures. One part will involve looking at existing concrete walls to determine what constitutes reasonable and achievable textures. The eventual goal is to provide the research results to ACI Committee 347 and get them to modify the guide to more reasonable and clear requirements.