LWD Correlation Day 2019
Edinburgh, Scotland
Light Weight Deflectometer (LWD) plays an increasing role in quality control of compaction work of foundations during road construction worldwide. Therefore it is very important that there is reason for highest confidence in the test results delivered by these devices.
During the recent „LWD Correlation Day 2019“ the objective was to understand if different devices (from different manufacturers or even those from the same) need to be calibrated with different factors to deliver the (nearly) exact results, even if every single device has it’s own valid calibration.
Comparation
To shed light into this matter Light Weight defletometers from the three manufacturers Dynatest LWD 3031, Prima 100 and TERRATEST 9000 LWD were compared. The devices of these three manufacturers are designed according to the specifications ASTM E2583 (USA), British standard BS EN 1924-2 (UK) and UNI 11531-1 (Italy).
Different series of trials were undertaken using around 40 different devices of these brands. The event took place at the Sports Labs headquarters in Livingston (close to Edinburgh, Scotland) on June 11, 2019 and was organized by Michael Gordon, technical director at WSP Scotland and expert in UK pavement design, maintenance and investigation projects. The event was supported by Highways England, Sports Labs, Transport Scotland and AECOM.
Sports Labs designed two different test areas: one inside – under laboratory conditions – and one outside – under conditions of a real construction site. The construction site was protected against rain and wind by a tent.
At the outside construction site there was a test situation of two different gravel layers with a thickness of 350 mm and 230 mm each. The idea was to compare the test results of two devices mounted on a trolley with the test results of the Light Weight Deflectometers. Each DynatestLWD 3031, Prima 100 and TERRATEST 9000 LWD had to perform 8 tests on this construction site with different stress moduli. On each position the tests had to be done with 100, 40, 60 kPA. These tests had to be performed at exactly the same position right where the two Falling Weight Deflectometers had done the tests before.
Two different rubber plates for testing
The inside test area under laboratory conditions was build up with two different rubber plates pieces of 80 x 80 x 10 cm taken from the tartan track of the Olympic games in London 2012 and a cube of 100 x 100 x 100 cm full of compacted gravel. Here different series of trials took place, with different stress moduli as well, again 100, 40, 60 kPA. On each positions three tests had to be performed with different stress modoli.
At the end of the event all users provided their test results as a CSV file to the organizer Michael Gordon. He will check thoroughly if different Light Weight Deflectometers of Dynatest LWD 3031, Prima 100 and TERRATEST LWD 9000 will deliver nearly identical test results under those varying conditions.
The entire setup and the organization of this international event was very professional. More than 40 devices from England, Scotland, Wales, France, Belgium and Germany were brought together to Sports Labs headquarters to make sure that quality control with TERRATEST 9000 LWD in construction site is the best, safest and most economic test method worldwide.