Tex-422-A, Measuring Temperature of Freshly Mixed Portland Cement Concrete

Transcription

1 Mixed Portland Cement Concrete Contents: Section 1 Overview...2 Section 2 Apparatus...3 Section 3 Procedures...4 Section 4 Report...6 Texas Department of Transportation 1 08/99 06/08

2 Section 1 Overview Effective dates: August 1999 June Section 1 Overview This test method provides a means for measuring the temperature of freshly mixed concrete. It may be used to verify conformance to a specified requirement for temperature of concrete. Units of Measurement The values given in parentheses (if provided) are not standard and may not be exact mathematical conversions. Use each system of units separately. Combining values from the two systems may result in nonconformance with the standard. Texas Department of Transportation 2 08/99 06/08

3 Section 2 Apparatus Section 2 Apparatus The following apparatus is required: Container made of non-absorptive material and large enough to provide at least 75 mm (3 in.) of concrete in all directions around the sensor of the temperature measuring device. The concrete cover must also be at least three times the nominal maximum size of the coarse aggregate. Temperature-measuring device, capable of measuring the temperature of the freshlymixed concrete to ± 0.5 C (± 1 F) throughout the entire temperature range likely to be encountered in the fresh concrete. Partial immersion liquid-in-glass thermometers (and possibly other types) shall have a permanent mark to which the device must be immersed without applying a correction factor. Texas Department of Transportation 3 08/99 06/08

4 Section 3 Procedures Section 3 Procedures Sampling Concrete The temperature of freshly-mixed concrete may be measured in the transporting equipment provided the sensor of the temperature measuring device has at least 75 mm (3 in.) of concrete cover in all directions around it. Temperature of the freshly mixed concrete may be obtained following concrete placement using the forms as the container. If the transporting equipment or placement forms are not used as the container, a sample shall be prepared as follows: Immediately prior to sampling the freshly-mixed concrete, dampen the sample container with water. Sample the freshly mixed concrete according to Test Method "Tex-407-A, Sampling Freshly-Mixed Concrete" except that composite samples are not required if the only purpose for obtaining the sample is to determine temperature. Place the freshly mixed concrete into the container. Calibrating Temperature Measuring Device Calibrate the temperature-measuring device as follows: Each temperature-measuring device used for determining temperature of freshly-mixed concrete shall be calibrated annually, or whenever there is a question of accuracy. This calibration shall be performed by comparing the readings on the temperature measuring device at two temperatures at least 15 C (30 F) apart to a standard. Texas Department of Transportation 4 08/99 06/08

5 Section 3 Procedures Measuring Temperature of Freshly-mixed Portland Cement Concrete The following table describes the procedure for measuring the temperature of freshly-mixed Portland cement concrete. Measuring Temperature of Freshly- Step Action 1 Place the temperature-measuring device in the freshly mixed concrete so that the temperaturesensing portion is submerged a minimum of 75 mm (3 in.). 2 Gently press the concrete around the temperature-measuring device at the surface of the concrete so that ambient air temperature does not affect the reading. 3 Leave the temperature-measuring device in the freshly mixed concrete for a minimum period of 2 minutes or until the temperature reading stabilizes, then read and record the temperature. 4 Complete the temperature measurement of the freshly mixed concrete within 5 minutes after obtaining sample. Texas Department of Transportation 5 08/99 06/08

6 Section 4 Report Section 4 Report Record the measured temperature of the freshly-mixed concrete to the nearest 0.5 C (1 F). Texas Department of Transportation 6 08/99 06/08