Q: The term green concrete is sometimes used in specifications, but it seems as if everyone defines it differently. What does the term mean?
A.: The American Concrete Institute (ACI) defines green concrete as concrete that has set but not appreciably hardened (Ref. 1). Saw manufacturers and sawing contractors refer to green concrete as concrete that has set but hasn't fully cured (Ref. 2). Both definitions are imprecise because the terms appreciably hardened and fully cured aren't defined.
Hardening refers to strength gain after final set has occurred. Thus, the ACI definition seems to imply that green concrete has reached final set but hasn't gained much strength. The saw manufacturers' definition implies that some hardening or strength gain has occurred because green sawing should begin when concrete won't spall or ravel at the cut edges. Green concrete can also mean freshly placed (presumably plastic) concrete (Ref. 3). However, the term is usually applied to concrete that has lost its plasticity. If the term is used but not defined in specifications, you should ask the specifier for a definition. Unfortunately, it probably won't be any more precise than the three definitions described above.
References
- ACI Committee 116, Cement and Concrete Terminology, ACI 116R-90, American Concrete Institute, Farmington Hills, Mich., 1990, p. 16.
- Target Catalog, Target Products, Kansas City, Mo., 1994, p. 95.3. J. Stewart Stein, Construction Glossary, 2nd ed., John Wiley & Sons Inc., 1993, p. 112.
