Recently, there have been appearing more cases of counterfeit and inferior geosynthetics under the trademark of reputable producers proven effective in the road construction society. How can a fake be distinguished and why is the use of inferior geosynthetics dangerous?
The most part of forged geosynthetic materials (geomats, geogrids, woven geotextile and so on) comes from China. They are usually made of low-quality second-hand raw materials by obsolete equipment. Such a fake can’t be eyeballed – lab testing is required. This problem is particularly important for using high-strength geofabrics and geogrids as reinforcement of slopes and retaining walls. Durability is the prevailing requirement for such material quality, which means that the strength parameters specified by the project (strength, elongation, creep) should be maintained within the whole service life of a reinforced soil structure. If a counterfeit fabric is made of second-hand material, it can lose 50% or more of its original strength in 5 years through negative impacts. As a result, the use of such short-lived materials may compromise the operational safety of a road structure.
As evidenced by geosynthetics producers, there have been more cases of providing road projects with materials with parameters deviating from either the project specifications or Rosavtodor’s new standards, such as GOST R 56338-2015 ‘Geosynthetic materials reinforcement of the road pavement base lower layers. Technical requirements’ and Road Industry Methods 218.2.046-2014 ‘Recommendations for selection and quality control of geosynthetic materials used in road construction’.
The root cause of the problem is rather simple. If the contractor has no financial responsibility over the constructed road section operation, it is obviously inclined to use the least costly, yet inferior in durability, and sometimes counterfeit, materials. Therefore, life cycle contracts is the main tool for the optimal selection of geosynthetic materials for a longer service life at a lower cost.
On the other hand, according to the valid law, geosynthetics are not a mandatorily certifiable product. Yet, the state-owned Avtodor and the Federal Road Agency have made substantial steps towards regulation of geomaterial supply to the federal projects. For example, Avtodor had mandated, via instruction No. PT-16p dated 14.02.2014, the entry control of all the geosynthetic materials through laboratory testing, and then launched the geomaterials quality control procedures applicable to Moscow – St. Petersburg highway construction.
For the purpose of ensuring the quality of geomaterials supplied to road projects, Rosavtodor issued instructions IG-1/48 and IG-1/49 on the use of geosynthetics. According to these instructions, all the materials used must comply in performance with the valid national standards and be supplied with the following documents attached:
- quality certificate for a batch of products with a mandatory reference to the company’s internal standard;
- copy of Rosavtodor’s approval of the company’s internal standard;
- test certificates with regard to all safety factors for durability assessment.
There are altogether seven safety (durability) factors per Road Industry Methods (RIM) 218.2.046-2014:
K1 is a factor allowing for strength reduction due to the structure mechanical damages;
K2 is a factor allowing for strength reduction through creep;
K3 is a factor allowing for strength reduction through deterioration of yarn contact points and weld joints or joint efficiency of the material structure elements;
K4 is a factor allowing for strength reduction due to ambient impact;
K5 is a factor allowing for strength reduction due to aggressive environment impact;
K6 is a factor allowing for strength reduction due to microorganism impact;
K7 is a factor allowing for strength reduction due to temperature impact.
Such an approach to regulation of material supplies to federal projects and the entry quality control, including sampling with regard to every batch and lab testing, will be undoubtedly effective, yet has a limitation. At the moment, there are only a few certified laboratories in the country that have a full set of equipment to perform third-party testing in strict compliance with GOST provisions. For instance, smaller tensile testing machines and 5 cm wide samples are often used for testing, which is contrary to GOST R 55030-2012 requirements of sample width of 20 cm. Since the number of laboratories does not even reach ten, it is physically impossible to test every batch of geomaterials supplied to road projects. Besides, taking into account the negative practice of using forged certificates and test reports, each laboratory should have a solid reputation in the road business, i.e be approved by a group of road experts, which has been the European common practice since long.
What steps can geosynthetic material producers make under the current conditions? The answer is to have geosynthetics tested by the certified laboratories possessing the proper equipment, including sufficiently sized tensile testing machines, to test high-strength materials.
Prior to purchasing materials for a project, contractors should pay special attention to test report and certificate authenticity, and that should include checking the protocol issuing laboratory accreditation as well. Entry-control testing should be entrusted to the laboratories possessing proper equipment, including sufficiently sized tensile testing machines for testing reinforcement materials.
In order to fight counterfeits, every batch and every roll of Geospan materials has a special number. This is a way for contractors to quickly define the authenticity of the materials supplied. We have witnessed at least 5 cases of delivery of geosynthetics of unknown origin to a road project. The materials were accompanied by forged test reports, and a third-party lab test showed their real strength below that indicated in the batch certificate. Gexa engineers were able in some cases to stop laying the fakes and have the counterfeit fact recorded jointly with the law enforcement authorities. You can find the list of companies suspected of such fraud in connection with Gexa products in the main page of geospan.ru site.
Due to the high cost of prototype testing, Gexa engineers could manage testing of woven geotextiles and volumetric geogrids in the factory lab in order to assess such an essential reinforcement material parameter as resistance to mechanical impact, or simply, damageability, in the process of laying and layer compacting (assessment of K1 factor as per Road Industry Methods 218.2.047-2014).
According to the Road Industry Methods, testing of resistance to mechanical damage should model the real conditions of material laying and be as close as possible to the conditions of the road structure designed. Therefore, medium sized sand layer of 30 cm thickness and 30 cm layer of graded dry bound macadam (fraction of 40 to 70) should be laid. Compacting was done by a supercompactor to reach factor 0.98 (over 20 trips). A geomaterial sample was accurately taken then (removal of the upper layer by a grader and manual removal of 15 cm of the lower layer).
According to the Road Industry Methods, testing of resistance to mechanical damage should model the real conditions of material laying and be as close as possible to the conditions of the road structure designed. Therefore, medium sized sand layer of 30 cm thickness and 30 cm layer of graded dry bound macadam (fraction of 40 to 70) should be laid. Compacting was done by a supercompactor to reach factor 0.98 (over 20 trips). A geomaterial sample was accurately taken then (removal of the upper layer by a grader and manual removal of 15 cm of the lower layer).
Geospan GT PP woven geotextile materials stand out for their void-free structure of strong, specially treated fibers. Partial damage of separate fibers by macadam does not result in any significant loss of the material strength. According to test results, geofabrics with strength of 30 kN/m and higher are practically not damaged where macadam contacts with sand, the residual strength exceeds 90%, and K1 factor is 1.08. The results obtained have confirmed the findings of our previous durability factor testing by TSK R&D Istitute’s laboratory. Low damageability differentiates woven geotextiles from woven geogrids and geomats as the latter’s joints can be damages by sharp macadam facets causing substantial reduction of the joint strength.
