CT-17 Quality Control
-
Upload
ukabir8549 -
Category
Documents
-
view
109 -
download
0
Transcript of CT-17 Quality Control
Concrete Technology
Harza Engineering Company
Quality Control
Purpose
To assure placement of consistent, uniform concrete in the work
To minimize variation in concrete properties such that the concrete will perform in a predictable manner
To achieve maximum economy in the work
Where does quality control begin? It begins in the production of
materials used in concrete (sampling and testing): Portland cement Pozzolan Coarse and fine aggregates
Uniformity of concrete production will be no greater than the uniformity of materials used in that concrete
How does quality control continue? Handling and stockpiling Batching and mixing Sampling and testing fresh concrete
Slump Air content Unit weight Temperature
Transporting and placing the freshly mixed concrete
How do we measure quality control? The most common measurement
is the uniformity of the compressive strength specimens determined from statistical concepts (ACI 214)
These same statistical concepts can also be applied to test results on materials used in the concrete, on the fresh concrete, and on other properties of the hardened concrete.
Primary criteria for application of statistical concepts
The primary criteria for application of statistical concepts is that the data to be analyzed has been developed from random sampling, and
At least 30 consecutive test results are available for analysis.
Normal distribution curve
Level of acceptance
Standards of Concrete Control(General Construction Testing) ACI 214
Excellent: Std. Dev. below 2.76 MPa Very Good: Std. Dev. of 2.76 to 3.45 MPa Good: Std. Dev. of 3.45 to 4.14 MPa Fair: Std. Dev. of 4.14 to 4.83 MPa Poor: Std. Dev. above 4.83 MPa
Within-test variation
Standards of Concrete Control(Field Control Testing) ACI 214
Excellent: Coefficient of variation below 3.0 percent
Very good: Coefficient of variation of 3.0 to 4.0 percent
Good: Coefficient of variation of 4.0 to 5.0 percent
Fair: Coefficient of variation of 5.0 to 6.0 percent
Poor: Coefficient of variation above 7.0 percent