Suitability test in conformance with DIN 14090

- Conclusion -

Goal of suitability test

The aim of the test is to examine the suitability of Netlon-Turf for use as turfed surface reinforcement on access roads for fire services in accordance with DIN 14090.

Subject of suitability test

The properties of Netlon-Turf were examined with regard to load-bearing capacity and the risk of skidding.

The following specifications were established in accordance with DIN 14090:

Load-bearing capacity:
Access roads for fire services must be able to withstand fire service vehicles with an overall mass of 16 tons and a 10 t load per axle. Hard standings must be able to withstand contact pressure of at least 800kN/m².

Risk of skidding:
The risk of skidding must be ruled out on access routes. In addition, we consulted the guidelines for planning, design and maintenance of vegetation-covered surface reinforcement (Richtlinie für Planung, Ausführung und Unterhaltung von begrünbaren Flächenbefestigunge 2008) issued by FLL, the German research institute for landscape development and design (Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau).

Conducting the test

Osnabrück University was commissioned with conducting the test. The suitability tests were conducted on 2 April 2016 by Prof. Martin Thieme-Hack (certified surveyor for landscape gardening and design) accompanied by Georg Armbruster (certified surveyor for soil testing) in Bad Griesbach.

Results of the test in respect of load-bearing capacity

Test with vehicle
Evenness in accordance with DIN 18202 was tested with a 4 m rod and the long control wedge under standard conditions and after a simulated intense rainfall event. A lorry was used with an overall mass of 33.3 t (corresponding to more than double the required 16 t) and a load per axle of 11t, in addition to a turntable ladder of 14.2 t.

  Required DIN values Standard conditions After rainfall event Result
Lorry 30 mm 0 - 13 mm 13 - 32 mm checked
Turntable ladder 30 mm 0 - 4 mm 0 - 6 mm checked

The gravel base course adjacent to the test surface demonstrated significantly higher occurrences
of deviation from the plane.

Plate-bearing test
The requirements according to FLL (2008) of 45 MNm² with respect to load-bearing capacity are not complied with.

Presumably this can be attributed to the gravel base course underneath the turf-bearing layer (due to the given test surface). Moreover, the Netlon fabric has favourable elasticizing properties, which do not allow any clear results in the plate-bearing test. On account of the following results with regard to shear strength and hardness, the load-bearing capacity can still also only be classed as adequate in this point.

Results of the test in respect of risk of skidding

Vehicle load and brake test
At no time was it possible to detect uncontrolled skidding, either under normal conditions or under the simulated heavy downpour event, either with the lorry or with the turntable ladder.

Shear strength and torsion
Shear strength and torsion provide indicative values for the absorption of horizontal forces on lawn surfaces and consequently for skid resistance.

With regard to shear strength, the values are unusually high compared with other tests conducted at Osnabrück University.

As there are no clear standards, DIN 15330-1 for artificial turf was referred to for torsion. The reference value given there is restricted to a maximum of 50 Nm, as a limit for sports use makes sense to keep impact lower for joints.

The very high results obtained of 58.1 to 88 Nm are very advantageous for fire service roads.

A Clegg Soil Impact test was conducted with results between hard and very hard.

Results of examinations in addition to the tests

Degree of compaction
Proctor density was determined in accordance with DIN 18127 using a sample of material and demonstrated a level of compaction between 102.3% and 99.8%. This complies with the requirements for road construction.

Organic substance
The percentages are between 1.6M.-% and 1.7M.-% as a result of determining loss-on ignition in accordance with DIN 18128. The FLL (2008) specifies a percentage by mass of organic substance between 1M.-% and 3M.-%.