Mixing and handling can significantly alter the air content of fresh concrete. Thus, field tests are used to ensure that the concrete has the proper air content prior to placing. Air content can be measured with the pressure, volumetric, gravimetric, or Chace air indicator methods. The pressure method (ASTM C231) is widely used, since it takes less time that the volumetric method. The pressure method is based on Boyle's law, which relates Figure 7.13 Consolidating concrete with an internal vibrator. pressure to volume. A calibrated cylinder (Figure 7.14) is filled with fresh concrete. The vessel is capped and air pressure is applied. The applied pressure compresses the air in the voids of the concrete. The volume of air voids is determined by measuring the amount of volume reduced by the pressure applied. This method is not valid for concrete made with lightweight aggregates, since air in the aggregate voids is also compressed, confounding the measurement of the air content of the cement paste. Main air valve Pressure gauge Pump Petcock B Air bleeder valve Petcock A - Air chamber - Clamping device "Extension tubing for calibration checks Bowl FIGURE 7.14 Pressure method apparatus for determining air voids in fresh concrete-Type B Meter. (reprinted, with permission, from ASTM C231, Figure 2, copyright ASTM Intermational, 100 Barr Harbor Drive, West Conshohocken, PA 19428)
Mixing and handling can significantly alter the air content of fresh concrete. Thus, field tests are used to ensure that the concrete has the proper air content prior to placing. Air content can be measured with the pressure, volumetric, gravimetric, or Chace air indicator methods. The pressure method (ASTM C231) is widely used, since it takes less time that the volumetric method. The pressure method is based on Boyle's law, which relates Figure 7.13 Consolidating concrete with an internal vibrator. pressure to volume. A calibrated cylinder (Figure 7.14) is filled with fresh concrete. The vessel is capped and air pressure is applied. The applied pressure compresses the air in the voids of the concrete. The volume of air voids is determined by measuring the amount of volume reduced by the pressure applied. This method is not valid for concrete made with lightweight aggregates, since air in the aggregate voids is also compressed, confounding the measurement of the air content of the cement paste. Main air valve Pressure gauge Pump Petcock B Air bleeder valve Petcock A - Air chamber - Clamping device "Extension tubing for calibration checks Bowl FIGURE 7.14 Pressure method apparatus for determining air voids in fresh concrete-Type B Meter. (reprinted, with permission, from ASTM C231, Figure 2, copyright ASTM Intermational, 100 Barr Harbor Drive, West Conshohocken, PA 19428)
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
Related questions
Question
Transcribed Image Text:Mixing and handling can significantly alter the air content of fresh concrete. Thus, field tests are
used to ensure that the concrete has the proper air content prior to placing. Air content can be
measured with the pressure, volumetric, gravimetric, or Chace air indicator methods. The pressure
method (ASTM C231) is widely used, since it takes less time that the volumetric method. The
pressure method is based on Boyle's law, which relates Figure 7.13 Consolidating concrete with
an internal vibrator. pressure to volume. A calibrated cylinder (Figure 7.14) is filled with fresh
concrete. The vessel is capped and air pressure is applied. The applied pressure compresses the air
in the voids of the concrete. The volume of air voids is determined by measuring the amount of
volume reduced by the pressure applied. This method is not valid for concrete made with
lightweight aggregates, since air in the aggregate voids is also compressed, confounding the
measurement of the air content of the cement paste.
Main air valve
Pressure gauge
Pump
Petcock B
Air bleeder valve
Petcock A
- Air chamber
- Clamping device
"Extension tubing for
calibration checks
Bowl
FIGURE 7.14 Pressure method apparatus for determining air
voids in fresh concrete-Type B Meter. (reprinted, with permission,
from ASTM C231, Figure 2, copyright ASTM Intermational, 100 Barr
Harbor Drive, West Conshohocken, PA 19428)
Expert Solution
This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
Step by step
Solved in 2 steps
Recommended textbooks for you
Structural Analysis (10th Edition)
Civil Engineering
ISBN:
9780134610672
Author:
Russell C. Hibbeler
Publisher:
PEARSON
Principles of Foundation Engineering (MindTap Cou…
Civil Engineering
ISBN:
9781337705028
Author:
Braja M. Das, Nagaratnam Sivakugan
Publisher:
Cengage Learning
Structural Analysis (10th Edition)
Civil Engineering
ISBN:
9780134610672
Author:
Russell C. Hibbeler
Publisher:
PEARSON
Principles of Foundation Engineering (MindTap Cou…
Civil Engineering
ISBN:
9781337705028
Author:
Braja M. Das, Nagaratnam Sivakugan
Publisher:
Cengage Learning
Fundamentals of Structural Analysis
Civil Engineering
ISBN:
9780073398006
Author:
Kenneth M. Leet Emeritus, Chia-Ming Uang, Joel Lanning
Publisher:
McGraw-Hill Education
Traffic and Highway Engineering
Civil Engineering
ISBN:
9781305156241
Author:
Garber, Nicholas J.
Publisher:
Cengage Learning