BS EN 14771:2012 pdf download
BS EN 14771:2012 pdf download.Bitumen and bituminous binders – Determination of the flexural creep stiffness – Bending Beam Rheometer (BBR).
5.2 Test specimen moulds, with the interior dimensions (8,4 ± 0.1) mm wide. (12.7 ± 0,1) mm deep and
(127 ± 5) mm long, fabricated from a suitable metal as shown in Figure 4. The thickness of the two end pieces
used for each mould shall not vary from each other in th.ckness by more than 0.1 mm.
NOTE Small errors in thickness of Ihe test specimen can have a large effect on the calculated modutos because the calculated modulus is a function of the thickness raised to the thid power.
6 PreparatIon of test samples
6.1 General
The laboratory sample shall be taken in accordance with EN 5.6 and prepared in accordance with EN 12594.
6.2 PreparatIon of moulds
Spread a very thin layer of petroleum-based grease onto the interior faces of the dry and clean metal mould sections. Press the plastic strips against the metal faces to force out any air bubbles. Cover the inside faces of the two end pieces with a thin film of de-moulding agent to prevent bituminous binder from sticking to the metal end pieces. Assemble the mould as shown in Figure 4 using 0-rings to hold the pieces of the mould together. Ensure plastic sheeting fits so that no raised edges occur on the cast beam.
NOTE 1 Plastic sheeting 0,08 mm to 0,15mm thick should be used. Transparency film sold for use with laser printers has been found suitable for this purpose.
NOTE 2 PolyvInyl alcohol and glycerol are found to be suitable as de-mould.ng agents It Is recommended to avoid silcono.based do-moulding agents that may affect the binder stiflnes
6.3 Preparation of test specimen
Pour hot binder into the metal mould that is at room temperature. Slightly overfill the mould- Pour the binder continuously toward the other end in a single pass Let the filled mould cool in the ambient temperature for 45 mm to 60 mm After cooling to room temperature. tnm the exposed face of the cooled specimen flush with the top of the mould using a hot knife or a heated spatula.
Store all the test specimens in their moulds at the room temperature prior to testlig. Testing shal be completed within 4 h alter specimens are poured.
NOTE 1 If the test is done at several temperatures, it may be practical to have longer times between pouring and testing. which may effect the pceasion of the test
Just prior to do-moulding, cool the mould containing the test specimen in a cold chamber or liquid bath for no longer than 5 mm in order to stiffen the test specimen so it can be readily de-moulded without distortion. In no cases shall the sample be exposed to a de-mouldirig temperature less than the test temperature.
At least two specimens per test temperature shall be tested.
NOTE 2 Excessive cooling may cause unwanted harderang of the binder and affect the test result
NOTE 3 During de-moiding, the specimen should be handled with care to prevent distortion. A warped test specimen may affect the measured values.
NOTE 4 Binders with very high viscosity can be poured into a pro-heated mould to prevent the binder cooling too quicicly and to ensure a more undorm specimen,
7 Procedure
7.1 Measurement
Clean the supports, loading head and bath liquid of any dust and coatings as necessary.
Check the adjustment of contact load and lest load poor to testing each set of test specimens. Refer to the operating instructions of the apparatus for checking and calibration
Select the first test temperature according to the expected stiffness level. Set the temperature control device to the desired test temperature and allow the apparatus to equilibrate. The bath liquid shall be at the test temperature ±0.2 C. Check that the temperature of the bath is stable for a minimum period o120 mm,
After de-moulding, immediately place the lest specimen in the testing bath and condition it at the testing temperature for (60 ± 2) mm before starting the test
NOTE 1 The mould base bar is a good support for the specimen.
Place the test specimen on the supports so that the width of the specimen as moulded will be the thickness of the test specimen (see Figure 5).
Establish the thickness of the test specimen immediately before testing by placing the test specimen on the supports. Apply a contact load of 25 mN to 45 mN to the specimen and record the reading of the displacement transducer. Invert the test specimen and obtain the second reading. If the two readings agree within 1,0 mm, calculate the average. If the two readings differ by more than 1,0 mm. the flatness of the test specimen is suspect and it should be discarded.
