Asphalt Tester | Modified Light Weight Deflectometer

Asphalt Tester ZORN AT 2.0 : new technical standard ensures traffic clearance

Prototypes of an asphalt tester LWD had been available from ZORN already since 2010, but have now been radically revised.

The device hardware can be taken apart into three component blocks that can easily be lifted by one person and transported in any passenger car. At the test site, the operator swiftly reassembles these three blocks in a few simple steps. When put together, the ZORN Asphalt Tester does not require a separate trolley or similar device for transport on site. The operator simply rolls the device comfortably between measuring points on large, integrated wheels. Once there, the drop weight section is moved from transport into the measuring position with a click and testing can begin.

The ZORN Asphalt Tester is controlled wirelessly by means of a tablet computer. The tablet computer is connected to the sensors of the tester via Bluetooth (acceleration & temperature). The easy-to-use control software also offers the possibility to seamlessly create test reports and send them to co-workers or clients online. ZORN Asphalt Tester - consistently digital and connected!

The revolutionary ZORN Asphalt Tester can be used alternately for the following test procedures.

Release test according to H VVA (FGSV institute Germany)

These German FGSV supplementary notes were published in 2022. They describe a procedure in which the deformation behaviour of an asphalt layer is continuously measured during the cooling phase by means of a modified LWD device.

The aim of this test is to help determine the appropriate cooling time for asphalt pavements before opening them to traffic, depending on the deformation behaviour of a freshly roller-compacted asphalt surface. The test can be used instead of or in addition to the known fixed cooling times (for Germany according to technical regulation ZTV Asphalt-StB, with 24 h / 36 h standard cooling periods).

For the deformation behaviour evaluation, a modified LWD device is used; according to the principles of an axial-dynamic plunger indentation test. Immediately after compaction, 5 consecutive load impacts are applied to the asphalt surface. Based on the resulting deflection and deflection differences, the deformation behaviour of the fresh asphalt surface can be assessed at the respective measuring point.

The way it works
The test device used is a modified Light Weight Deflectometer (LWD) according to German technical standard TP BF-StB, Part B 8.3 (or ASTM E2835 respectively). For use as an asphalt test device, in difference to the load plate, a test plunger (non-bevelled, flat, diameter 50 ±0.1 mm) is loaded by a falling weight with a mass of 15 kg, producing an impact force of 9.42 kN, with an impact duration of (17 ±1.5) ms. If all 15 measuring points show a value AVF = 100%, the road can be opened to rolling traffic.
Technical equipment:

  • Modified Light Weight Deflectometer
  • For release tests according to "Supplementary notes on opening asphalt pavements to traffic" (H VVA), FGSV Germany, edition 2022
  • Test plunger (non-bevelled, flat surface, diameter 50 ±0.1 mm)
  • Loading mechanism with 15 kg drop weight
  • Max. impact force 9,42 kN, impact duration 17 ±1,5 ms
  • MEMS acceleration sensor for precise deflection measuremnts
  • Temperature sensor for monitoring the asphalt surface temparature
  • Temperature range asphalt surface ≤ 60° C
  • Robust outdoor tablet computer 8‘‘ with ZORN H VVA App for wireless device control, automated data collection and calculation of release coefficient AVF, production of complete protocols according to H VVA
  • Two integrated, temperature resistant wheels for comfortable transport and moving the device between measurement positions.
  • Transport case
  • Expandable with asphalt modulus measurement kit for determination modulus measurement Evd Asphalt (ZORN INSTRUMENTS 2010)

Get the data sheet for download here.

Dynamic Deformation Modulus

A further application for the ZORN Asphalt Tester, which is particularly interesting for research and university studies, is the determination of elastic surface deformations and a Dynamic Deformation Modulus for asphalt (EVD ASPHALT).

Based on theoretical considerations of Weingart et al., ZORN INSTRUMENTS have offered a prototype style LWD Tester for asphalt for some time (ZORN AT 3000). Technically, the device is also based on the principle of an axial-dynamic plunger penetration test. This asphalt tester determines the penetration depth and speed of test plungers of different diameters under a dynamic load. Using the measured maximum penetration depth (deflection) and a set of further variables, a deformation modulus is determined according a specific formula. More details you find here.