Almost two years ago, ACI released ACI 347.3R-13, Guide to Formed Concrete Surfaces. The American Society of Concrete Contractors was concerned that the guide lacked clarity and could put contractors at risk of rejection of wall panels due to unachievable features. This led to a research project, reviewed by Ward Malisch during the recent ASCC Annual Meeting, to identify “complex or confusing requirements” and then fund Concrete Industry Management students at Middle Tennessee State University to attempt to measure the “surface void ratio,” or bugholes. This proved to be difficult and highly variable. The work continues with the eventual goal of getting ACI to modify the guide to more reasonable requirements.
Trump’s Concrete Wall
I had been wondering about Republican presidential candidate Donald Trump’s proposed wall at the border with Mexico and whether he envisioned it being made of concrete. Trump has used concrete in the past, such as at Chicago’s Trump Tower which is the tallest reinforced concrete building in the U.S. But a 2,000-mile-long wall in some of the most inhospitable terrain in the country is quite another matter. Then I came across an amusing exploration of the topic by a structural engineer who concludes that the best approach would be precast concrete posts and panels that would require 12.6 million cubic yards of concrete and about 5 billion pounds of reinforcing steel. I guess I’ll have to vote for him after all!
Tall Wood Buildings
We ran a couple of articles on our website in September about the increase in tall wood buildings across North America — in the 12-story range or higher. It seems that the U.S. Department of Agriculture has decided that wooden buildings are a good thing, despite the increased fire danger. If this practice became commonplace it could result in a 10% or more reduction in the concrete market. The National Ready Mixed Concrete Association is considering increasing dues to mount a response and other industry associations are looking at what can be done. This is a serious threat to the concrete industry, but even more serious is the threat to the safety of building tenants and visitors. Whatever happened to hugging a tree?
Letter from Alcatraz
Our friend Tanya Komas reports that her current group of repair interns are doing great things on Alcatraz Island to repair and rebuild the landmark structure. The work is being done through the Concrete Preservation Institute with support from industry sponsors and the National Park Service. For this fall session, a crew of four military veterans and three other young people are working on an area that is inaccessible during the summer due to the sensitive bird population. Sounds like a great way to spend three months.