They conclude that this procedure is useful for monitoring crack growth in concrete due to fatigue. Based on the appearance of the fracture surface, which shows a combination of both aggregate fracture and bond failure, they feel that fracture toughness is not a pertinent material property. However, they state that an effective fracture toughness might be a significant material property if related to specific material and specimen variables such as aggregate size and gradation, and proportions of the mix, and if the calculation considers the nonlinear material re- sponse of concrete. A number of investigators do not feel that the Griffith theory of linear fracture mechanics is di- rectly applicable to all concrete 2. Some like Swartz, et a1.
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They can expose reinforcing steel to oxygen and moisture and make the steel more susceptible to corrosion. While the specific causes of cracking are manifold, cracks are normally caused by stresses that develop in concrete due to the restraint of volumetric change or to loads which are applied to the structure.
Within each of these categories there are a number of factors at work. A successful crack control program must recognize these factors and deal with each of them, in turn. This report presents the principal causes of crack- ing and a detailed discussion of crack control pro- cedures. The body of the report consists of seven chapters designed to help the engineer and the con- tractor in the development of effective crack control measures.
This report is an update of a previous committee report, issued in In the updating pro- cess, many portions of the report have undergone sizeable revision, and the entire document has been subjected to a detailed editorial review.
Chapter 2, on crack mechanisms, has been completely rewritten to take into account the experimental and analytical work that has been done since the completion of the first committee report.
Chapter 6, on crack control in concrete layered systems, is new to the report and deals with a form of concrete construction that was in its infancy at the time the first report was drafted. Individual chapters on crack control in re- inforced and prestressed concrete members have been condensed into a single chapter, Chapter 4, on crack control in flexural members.
The resulting pre- sentation is more concise and, hopefully, more useful to the structural designer. Chapter 5, on long-term effects, details some interesting findings on the change of crack width with time. Chapters 3, 7, and 8, which consider drying shrinkage, mass concrete, and construction practices, respectively, have been expanded and updated to take into account the most recently developed procedures in these areas.
In ad- dition, new sections have been added to Chapters 7 and 8 which provide specific guidance for the devel- opment of crack control programs and specifications.
The committee hopes that this report will serve as a useful reference to the causes of cracking and as a key tool in the development of practical crack con- trol procedures in both the design and the construc- tion of concrete structures.
224R-01: Control of Cracking in Concrete Structures (Reapproved 2008)
CRACKMON® 224R Crack-Width Comparator
ACI 224 . 3 R-95 Joints in Concrete Construction Reported by ACI Committee 224