Road building and civil engineering

Many thousands of users already value the measuring devices developed and produced completely in-house by ZORN INSTRUMENTS as precise tools for quality assurance on road building and civil engineering sites in more than 80 countries of the world.

In the ZORN INSTRUMENTS range, test laboratories, road construction authorities and construction companies all find suitable solutions for testing compacted soil materials or for quality tests while laying asphalt.

The Lightweight Deflectometer ZFG launched by ZORN INSTRUMENTS at the start of the 1990s is already a classic in road building and civil engineering. Using this smart instrument, the user can check the load-bearing capacity of the existing subsoil, the complete road subbase, as well as base courses without binding agent in road surface construction.

ZFG - Lightweight Deflectometer

The Lightweight Deflectometer ZORN ZFG for undertaking the so-called "dynamic plate load test" is setting standards in the area of compaction testing and assessment of the load-bearing capacity of non-cohesive soils. The usage of the now some 11,000 ZORN ZFG in different series (as of 2019) is covered by recognised standards worldwide, such as TP BF-StB, Part B 8.3 or ASTM-E 2835-11.

To the Falling Weight Deflectometer

Along with conventional gravel, sand, ballast or chippings, it is also possible to test recycled construction materials as well as material mixtures using a ZORN ZFG. The reliable test results enable the user to make immediate decisions about construction progress; e.g. continuing or ending prematurely the compaction, initiation of measures for soil improvement or material replacement.

The ZORN ZFG is based on complex scientific principles and provides exact data. Despite its basis on complex scientific principles, it is extremely easy for the user to operate. Construction companies therefore like to use it for their own monitoring of the quality of the construction.

According to the current German road construction standard ZTV E-StB 17, quality tests with the Lightweight Deflectometer are accepted by the client as the sole inspection test.

It is possible to use the Lightweight Deflectometer in parallel with construction site operations. Also, unlike other methods, tests using the Lightweight Deflectometer do not require any additional equipment (e.g. impact tools or a heavy vehicle as counterweight). This situation helps the user to achieve more efficient construction site processes and reduces the costs for quality assurance to a necessary minimum.

The ZORN AT Asphalt Tester

The ZORN AT is currently the world's most modern instrument for the evaluation of the quality of the compaction of asphalt and for determining the suitability for traffic of asphalt layers.


With the "Hinweispapier frühere Verkehrsfreigabe" (information paper on early opening to traffic of asphalt road surfaces) (draft 2019) published by the Forschungsgesellschaft für Strassen- und Verkehrswesen e.V. (FGSV), an initial technical standard for the usage of the ZORN AT is available. The revolutionary measuring device enables the user to determine in a binding manner the suitability for traffic of asphalt layers. The paper supplements the information on waiting periods for laying binder and wearing courses stipulated in the German code for laying asphalt. The desire for shorter construction times can therefore be better addressed while safeguarding the quality of the asphalt at the same time. The inclusion in the contract of tests using the ZORN AT also helps to prevent legal problems between the contractor and client.

As a tool for the determination of the quality of the asphalt compaction on the spot, the ZORN AT is also a valuable addition to the obligatory material tests in the laboratory.

The test with the ZORN AT is based on the principle of operation of the lightweight deflectometer for soil. Like the ZORN ZFG, it is remarkably easy to use. The latest sensor technology in the ZORN AT safeguards the highest precision and repeatability of the tests, even on hardened asphalt layers.

Click here to go back to the ZORN AT and to the Lightweight Deflectometer ZFG.