The falling sand method is used to evaluate the wear resistance of the tested sample surface, which is suitable for A1 and A2 protruding road signs. Class A3 can be used by reference.
2. Test device composition:
◆The test device consists of a vertical sand guide pipe, a calibration funnel, a filter screen, a sample holder and a sand collector. Sand guide pipe: It can be composed of a solid-walled plastic pipe with an inner diameter of not less than 150MM and a smooth inner wall. The length is 2850MM. The non-verticality of the sand guide pipe is not more than 0.2°.
◆Calibration funnel: The upper mouth size of the calibration funnel is 120MM×40MM, the height is 100MM, and the four-sided slope angle is 45°. The four sides of the upper mouth should be straight and sharp to ensure that the sand falling on the edge of the mouth does not change its direction when it falls into the bucket. The function of the funnel is to ensure that the sand directly falling into the mouth does not deviate from the ground and hits the protruding road sign as vertically as possible, while the sand falling outside the mouth is deviated to the outside of the bucket and cannot hit the protruding road sign. The calibration funnel should be able to move up and down, left and right, and back and forth to facilitate adjustment of the amount and uniformity of sand passing through the funnel.
◆Filter mesh: The filter mesh is located on the upper part of the sand guide pipe, and the mesh size is a standard mesh larger than 850UM. The function of the net is to establish the starting point of falling sand, and the other is to limit the flow rate of falling sand. It is required that the distance between falling sand and the net should not be greater than 30mm.
◆Sample rack: It is used to hold the tested sample firmly, keep the base surface of the sample vertical, and conveniently center the sample with the sand guide tube and the calibration funnel. The height of the tested sample can be adjusted freely to make the upper edge of the funnel and the funnel. Keep the upper mouth no larger than 150mm, and adjust the horizontal direction so that the front edge of the bottom edge of the sample retroreflective surface is parallel to the long side of the funnel. The sample holder should not block the free flow of falling sand.
◆ Collector: 1 300MM×500MM enamel tray or other containers can be used. In order to prevent the sand falling into the calibration funnel from splashing or external sand from splashing in, the lower mouth space of the funnel can be enclosed by the same soft cloth cover as the lower mouth of the funnel.
c) 通过校正漏斗的试验砂的质量应为(2.5+0.020 8X)KG,允差±2％;
3. Test steps:
◆Install and adjust the equipment and the tested sample in place, and ensure that the distance from the top of the sand guide pipe to the edge of the bottom of the tested sample is 3.00M±0.03M.
◆Take enough test sand and drop it evenly on the filter screen on the upper part of the sand guide tube at a speed of 0.4KG/MIN-1.0KG/MIN. Pay attention to the uniformity and position of the sample impacted by the falling sand, and always follow B.6 The method to calibrate the uniformity of the test device.
◆Collect and weigh the sand that has passed the calibration funnel. The weighed sand includes the sand that hits the sample and the sample holder is splashed to the outside, but does not include the part that has not passed through the funnel. When it is found that the amount of sand collected does not meet 2.5KG± When 0.050KG is required, the test device should be calibrated in accordance with the method in B.6.
◆Remove the tested sample, clean it with a soft cloth, and measure the luminous intensity coefficient of the impacted retroreflective surface.
◆Discard the used test sand. The test sand should only be used once for each test and should not be reused.
◆Test device calibration
The falling sand should pass through the calibration funnel uniformly, and its uniformity is verified by placing at least 10 vials with a diameter of about 10MM at the position and height of the protruding road signs under the funnel. When enough sand falls through the funnel, at least one vial collects at least 5G of sand, and the weight of the sand in the least collected vial reaches at least 75% of the weight of the sand in the most collected vial to qualify the test device. After determining the flow stability of the device, adjust its uniformity and the amount of sand passing through the funnel by adjusting the top and bottom of the funnel and the total amount of sand as needed.
◆ Modification of test equipment
When the bottom side of the measured raised road sign is greater than 100MM, the entire device should be corrected. Assuming that the bottom side of the measured raised road sign is (100+X)MM, the correction content is as follows:
The long side of the upper mouth of the correction funnel is (120+X) MM;
The inner diameter of the sand guide pipe should be at least (150+X) MM;
c) The quality of the test sand passing the calibration funnel should be (2.5+0.020 8X) KG, with a tolerance of ± 2%;
d) The flow rate of sand falling through the funnel should be maintained at (0.4+X/300)KG/MIN―(1+X/120)KG/MIN
注：在ASTM D 4280-2004中指定使用位于美国中部St,Peters或Jordan的砂岩沈积砂。
Four, matters needing attention:
Temperature 23°C± 2°C, relative humidity (50±25)%.
◆Sand for testing
The test sand should use natural quartz sand with extremely high silica content.
The particle distribution of this kind of quartz sand should meet the following requirements: after 10 MIN, no more than 10% of the total weight is retained on the No. 20 sieve (850 UM), and no more than 10% of the total weight is passed through the No. 30 sieve. (600UM).
Note: ASTM D 4280-2004 specifies the use of sandstone sedimentary sand located in St, Peters or Jordan in the central United States.