The Concrete Reinforcing Steel Institute provides the best tools for understanding steel reinforced concrete.
By Sue McCraven
Editor’s Note: Work in the precast industry inevitably involves a requirement or specification established by one of many associations with acronyms such as ASTM, ACI and CSA1. This series introduces you to these associations and their histories and a perspective on why they matter to precasters. This article takes a close look at the Concrete Reinforcing Steel Institute.
Standing on a wobbly walkway roped off with yellow caution tape, a young engineer gapes up through the dusty air as a 12-ft-high steel I-beam inches upward. Once in position, this monster beam will carry the weight of a power plant’s multi-story boiler. In awe, this green engineer suddenly realizes steel’s incredible potential: strong, dependable, flexible. Steel: It is love at first sight for engineers. But the construction romance gets better when steel marries concrete.
Concrete and steel were made for each other. The two groove together as one – the same coefficient of thermal expansion. One material yields its tensile strength, the other delivers its formidable compressive strength. A magnificent symbiotic structural union like no other on earth. Go ahead, build anything you want! Steel and concrete are an engineer’s dream come true – and the Concrete Reinforcing Steel Institute (CRSI) keeps that dream alive.
Rodbusters and CRSI: the real deal
If you want to know anything at all about steel reinforced concrete, CRSI is the place. CRSI (www.crsi.org), founded in 1924, is a national trade association that is the authoritative resource for all information related to steel reinforced concrete construction. Its engineers can provide all manner of knowledgeable technical assistance, from how to easily decipher convoluted steel rebar specifications to understanding how the latest discoveries in steel technology will make rust a thing of the past.
CRSI’s “Manual of Standard Practice” is as important to a young engineer as protein is to an athlete: You can build on it and you can grow on it. CRSI’s publications are straightforward, easy-to-use, ready resources for the design office or the construction site.
Rodbusters use CRSI books. Rodbusters are the real deal, and if you don’t believe this, just get to know one on any big construction site and become educated. “Placing Reinforcing Bars” is the little brown book that has been at the foundation of every great structural engineer.
Rust: Does it matter?
In school, all the steel building components shown in books are perfectly black and shiny. In the field – the real world – steel tends to look a little orangey. But, as it turns out, that’s OK. A little rust never hurt anyone. If you want to know how much rust on a reinforcing bar is still all right to use, CRSI can tell you.
CRSI can provide all the important information that anyone working with steel and concrete needs to know, and all the information from CRSI works the right way in the real world. How many organizations can say that?
While it is true that steel and concrete work together like no other building materials in the world, like rodbusters, you don’t want to mess with them. There are rules for making reinforced concrete perform to its maximum in the construction world, and these rules are not to be trifled with. Concrete and steel will give you lifetimes of strength and service to depend upon, but if you don’t understand their basic requirements, they can be very dangerous and unforgiving.
Reinforced concrete is very sensitive
Designing with steel and concrete is an exacting business. Yes, steel is strong. Yes, concrete is strong. Together as a composite building material, they’re unbeatable. But the margin of error in reinforced concrete design is very small indeed. The amount (or area) of steel put into a given cross section of concrete must be correct. Steel rebar must be located precisely. Concrete cover over steel reinforcing bars cannot slip below a codified specification, or you could have structural failure.
The following are two of the most commonly asked questions for CRSI and the responses it provides:
QUESTION: If there is rust on the steel reinforcing bars, are they still OK to use?
Answer: There are a number of things that can get onto the surface of rebar and affect the bond strength between the rebar and concrete. Oil and grease need to be wiped off with a solvent. Dirt and mud can be washed off or cleaned using a wire brush. However, rust, mill scale and surface irregularities actually increase the bond, because they increase the roughness of the rebar. So yes, rust is OK – except if there is so much rust that the weight, dimensions or cross-sectional area of the rebar have reduced to below the minimum specified by the material standard.
QUESTION: Is it OK to bend or to re-bend reinforcing bars in the field?
Answer: The bending or re-bending of steel reinforcing bars in the field is one of the most common and one of the most controversial procedures that frequently come into question related to cast-in-place reinforced concrete construction. These situations may arise as the result of unplanned occurrences (when rebar is accidentally run over by a vehicle, for example) because of on-site corrections and adjustments, or as intentional building changes. The best advice for dealing with these situations is to always involve the architect/engineer and to follow the guidelines in the ACI 318 Building Code.
Sue McCraven, NPCA technical consultant and Precast Solutions magazine editor, is a civil and environmental engineer.