“Formwork is a special part of the concrete business,” says Rolf Spahr, “but it is used in all parts—bridges, high-rise structures, parking decks. A few years ago, Dan Baker with Baker Concrete, asked me to get involved in the American Concrete Institute to bring my formwork knowledge. After looking at the various guides and documents, such as ACI 347, 301, and 117, I realized that there was no clarity on surface texture. ACI 117 talks about deviation from plane but I thought that was not enough. The goal was to define the various aspects of a formed surface, and the result was the new ACI 347.3, Guide to Formed Concrete Surfaces.”
The new guide is based around four concrete surface categories (CSC). CSC1 might be a basement wall while CSC4 would be high quality architectural concrete. Within each category there are requirements for texture, surface void ratio, color uniformity, surface irregularities, and construction and facing joints. Each of those surface characteristics typically also has four levels—for example a surface void ratio level 1 (SVR1) allows a maximum void area of 1.2% while an SVR4 allows only 0.3% voids
Shortly before this document was released by ACI in early 2014, the American Society of Concrete Contractors came out opposed to some of the provisions, feeling they were vague and difficult to measure. ASCC stated that ACI 347.3 defines CSC2 as “normal requirements that standard formwork and placement practices should yield without any special effort and at an average relative cost.” But they felt that no effort had been made to show that this statement was true. Nonetheless, ACI released the guide. ASCC is currently sponsoring research at Middle Tennessee State University through the CIM program “to assess the impact of this ACI guide and the measurement of formed concrete surfaces to determine the appropriateness of the German Concrete Association recommendations to U.S. concrete construction practices.”
Spahr counters that the objective was not to bring something from Germany but to use the German document as the basis of a guide that “would make life easier and more understandable for contractors. No one is forced to use the guide and the contractor can decide how to create the defined surface.”
Spahr comes at this from many years in the industry in Germany and working all over the world. “As a kid, I wanted to get into the construction business. I apprenticed as a bricklayer, learning from scratch, then went to engineering school and ended up working in an engineering office.” He soon moved to MEVA Formwork Systems and in 1978 met Dan Baker at the Bauma show in Munich. Baker encouraged MEVA to make their modular forms in inch-pound sizes, which they did. Today, although MEVA is not the biggest of the European formwork companies in the U.S. the company’s formwork with its plastic alkus facing panels, is used on many high-profile and high-tolerance projects.
Spahr and ACI Committee 347 are trying to educate contractors and architects about the new guide—he recently presented a webinar to ASCC members. “It will take some time to gain experience with this,” he says, “but I believe it will put contractors in a better position with the architect or engineer. It will push people to sit together as a team. Talking together is always the best way.”