1、Standard Method of Test for Determining Formwork Pressure of Fresh Self-Consolidating Concrete (SCC) Using Pressure Transducers AASHTO Designation: T 352-141American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3b T 352-
2、1 AASHTO Standard Method of Test for Determining Formwork Pressure of Fresh Self-Consolidating Concrete (SCC) Using Pressure Transducers AASHTO Designation: T 352-1411. SCOPE 1.1. This method covers the measurement of formwork pressure of fresh self-consolidating concrete (SCC) using pressure transd
3、ucers attached to formwork. 1.2. This is a field test with the intention of measuring formwork pressure during placement of SCC. 1.3. The text of this standard references notes that provide explanatory information. These notes shall not be considered as requirements for this standard. 1.4. The value
4、s stated in SI units are to be regarded as the standard. 1.5. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to esta
5、blish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. ASTM Standard: C125, Standard Terminology Relating to Concrete and Concrete Aggregates 3. SIGNIFICANCE AND USE 3.1. This method is applicable when there
6、is a concern about SCC form pressures that may exceed the rated strength of the formwork. SCC shall be defined by ASTM C125. Note 1Formwork less than or equal to 3 m (10 ft) tall constructed of commercial forms rated at 57.5 kPa (1200 lb/ft2) or greater may be able to resist the SCC pressures encoun
7、tered in the field; however, the engineer is still responsible for the formwork design. 4. APPARATUS AND MATERIALS 4.1. Pressure TransducerA suitable pressure transducer for measuring pressure from SCC. 2015 by the American Association of State Highway and Transportation Officials.All rights reserve
8、d. Duplication is a violation of applicable law.TS-3b T 352-2 AASHTO Figure 1Pressure Transducer 4.2. Data Acquisition SystemA suitable data acquisition interface for obtaining pressure readings from pressure transducers. 4.3. BracketA bracket conforming to the pressure transducer and formwork geome
9、try shall be used for attaching the pressure transducer to the formwork. Figures 2 and 3 show one such bracket system. Figure 2Bracket for Attaching Pressure Transducer to Formwork 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a vi
10、olation of applicable law.TS-3b T 352-3 AASHTO Figure 3Bracket with Pressure Transducer Attached to Formwork 4.4. Portable Hand Drill and BitA suitable drill and bit for drilling pressure transducer access holes. 4.5. Baby Powder and Cellophane WrapSuitable materials for covering the pressure transd
11、ucer face. Note 2A Vishay Model P3 Strain Indicator and Recorder with Honeywell Model AB/HP pressure transducers have been used for measuring pressures from SCC. The Vishay unit will accommodate four pressure transducers, and the required access hole for the Honeywell Model AB/HP pressure transducer
12、 is 35 mm (13/8in.) in diameter. 5. PROCEDURE 5.1. Prepare access hole for pressure transducer: 5.1.1. Drill an appropriate size access hole through the formwork for the pressure transducer that will allow measurement of pressure. 5.2. Mount pressure transducer: 5.2.1. Mount the pressure transducer
13、to the formwork using the bracket system. The pressure transducer face shall extend through a hole drilled in the formwork and shall align flush with the inside form surface. 5.2.2. The face of the pressure transducer shall be protected with a light dusting of baby powder and a single layer of cello
14、phane wrap on top. Note 3This technique prevents direct contact of the SCC with the pressure transducer face while ensuring measurement of pressure. 5.3. Location of pressure transducers: 5.3.1. Install a minimum of one pressure transducer at or near each point of SCC placement. The first pressure t
15、ransducer below the point of SCC placement shall be approximately 300 mm (12 in.) above the base of the formwork. Additional pressure transducers shall be installed above the bottom transducer at the direction of the formwork design engineer. 2015 by the American Association of State Highway and Tra
16、nsportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 352-4 AASHTO Note 4The reason a pressure transducer is installed at or near the point of SCC placement is due to the higher formwork pressure at this location. Pressure transducer(s) are important due to
17、the higher formwork pressures that may be generated during an SCC placement application. Be advised that pressure transducers may malfunction for various reasons. Adding additional pressure transducers creates redundancy and reduces the probability of total transducer failure. Additional transducers
18、 should be placed a minimum of 450 mm (18 in.) apart. Instrumentation with pressure transducers does not replace proper monitoring of formwork and does not assure formwork safety. 5.4. Recording pressure and form filling rate: 5.4.1. The pressure shall be observed and recorded periodically to ensure
19、 that the pressure remains under the rated strength of the formwork during the pour. The calculation and recording of form filling rate during the pour should also be performed periodically to evaluate the pour rate influence. Note 5The measured pressure will rise as the formwork is filled with SCC
20、but will eventually slow down and start falling as the SCC begins to gel and stiffen. Formwork pressure is also a function of the form filling rate. If the rate is low, the maximum pressure will be relatively low. If the rate is very high, the pressure may approach hydrostatic pressure. It is cautio
21、ned that if the form filling rate is significantly increased later in the day, formwork pressure above a pressure transducer location will likely be higher than the pressure at the transducer. In addition, stopping and subsequently starting a pour will cause the pressure to fluctuate. Therefore, it
22、is important to maintain relatively constant pour rates through the day. 6. REPORT 6.1. The report shall include the following: 6.1.1. The formwork rating by the manufacturer, 6.1.2. The measured pressure at various times during the pour, and 6.1.3. The peak pressure. 6.2. The report should include
23、the form filling rate. 7. KEYWORDS 7.1. Bracket; data acquisition system; form filling rate; formwork pressure; hydrostatic pressure; measured pressure; pressure transducer; SCC; self-consolidating concrete. 1Formerly AASHTO Provisional Standard TP 93. First published as a full standard in 2014. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
