Frank Georg Schulz | TERRATEST

What is ASTM E2835-11 International Standard for Calibration of LWD?

Apr 23rd 2015 at 4:13 AM

Light weight deflectometers are reliable field testing devices that are used to determine soil's compaction quality. They are some of the most important testing devices for various construction projects, like road and highway construction. Soil and its aggregate layers must provide a stable and stiff foundation to ensure that the road can last long. LWDs can be helpful during inspections and construction as they determine if the pavement foundation materials are compacted enough to suit the soil conditions. LWDs are portable, lightweight, and easy to use, and they can provide a more accurate measurement of the rigidity of unbound materials during construction. To ensure the quality of a LWD, it must undergo testing and pass certain calibration standards.

ASTM E2835-11 is an American standard for calibrating light weight deflectometers. It is internationally recognized as a test method to measure deflections with a portable impulse plate load test device. ASTM E2835-11 ensures that light weight deflectometers can operate under the toughest conditions in construction sites. Hence, all LWDs with an ASTM E2835-11 calibration certificate should be able to withstand rain, extreme temperatures, vibrations, and dust.

If you find anything wrong with your light weight deflectometer, repairs and recalibration should be done according to ASTM E2835-11 standards. A LWD must come with a calibration certificate that is based on the ASTM E2835-11 international standard. Moreover, it must be accredited by the German Federal Road Research Institute.

The ASTM E2835-11 standard test method determines the plate deflection resulting from impulse load application. Deflection is measured at the top of load plate's center. A load plate that is in perfectly uniform contact with an unbound material underneath the plate depicts a load plate deflection that is similar to the deflection of the surface of the unbound material. Despite that, even unbound materials typically cannot achieve a completely uniform contact at all times. A test surface must be smooth and clean without any protruding material or loose granules. Fine sand must by applied as a thin layer over the test point on a gravel surface.

The applied load may affect the volume of the materials for the pavement foundation. In this sense, the volume is the function of the magnitude of the plate size, rigidity, and load. Likewise, the volume can pertain to the stiffness, sheer strength, loading rate, and buffer stiffness of the materials used for the pavement foundation. Hence, you must be careful when analyzing results. Data from the portable impulse plate load test can be retrieved under different conditions other than when a heavy moving wheel load goes over the surface of the pavement after completion of the construction project.

About The Author:

TERRATEST GmbH is world leader in development and manufacturing of Light Weight Deflectometers for dynamic load plate test. They offer the world’s first light weight deflectometerTERRATEST 5000 BLU” with Bluetooth and voice navigation. For more information about their products visit their website!

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