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Bentofix®THE GENIUS BEHIND

ENGINEERINGIQ

The Inventor of Needle-punched Geosynthetic

Clay Liners. Outstanding Quality and Longest Experience.

Bentofix® - The Original!

Bentofix® IQ addresses four subjects key to understanding geosynthetic clay liners (GCLs): Technics,

Quality, Application and Ecology. It describes the intelligence and importance of this product type,

which was invented by NAUE in 1987, and highlights the intelligent use of needle-punched GCLs in

sealing applications. Today, the Bentofix® IQ approach is guided by the classical elements of water,

fire, earth and air as critical issues such as proper GCL production, design, application and installa-

tion. Bentofix® IQ encourages GCL users to utilize these classical elements to understand those four

key GCL subjects: Technics (water), Application (earth), Quality (fire) and Ecology (air).

The high-quality, high-swellingpowdered sodium bentonite inBentofix® geosynthetic clay lin-ers makes Bentofix® an excep-tional barrier against liquids. Thedurable, robust nonwoven geo-textile outer layer increases shearstrength and interface friction angles. Whether installed in dry orwet conditions, Bentofix® providesa cost-effective, long-term barrierfor canals, infiltration-preventingcaps over landfills, composite linersystem containment support, andother applications requiring stronghydraulic performance. Hydraulic conductivity:When hydrated with fresh water,the powdered sodium bentonite

in Bentofix® swells to form a low permeability gel layer with a hy-draulic conductivity equivalent toor better than a thick compactedclay liner (CCL). This conductivityis exceptional even under low confining stress and high waterheads. In fact, the higher the con-

fining stress over the Bentofix®GCL, the better it performs. Evenafter freeze-thaw or dry-wet cy-cles the Bentofix® still performs as a barrier. Furthering the security

of any barrier installation, Bento-fix® takes full advantage of theswelling power of bentonite pow-der. Panel overlaps are treated withan extra 50 cm of bentonite alongthe longitudinal edges. No extraseaming or welding is required tosecure these overlaps as both theweight of the material and the

swelling properties of bentoniteprovide the effective, long-termseal. Where appropriate for the design, e.g. water proofing, pondapplications, intimate contact toother membranes, Bentofix® BFGwith extra bentonite impregnatedduring manufacturing across the

entire surface of Bentofix® is thesolution. Regardless of the situa-tion, the strong hydraulic con-ductivity of Bentofix® possessesthe durability and swell capacity

to serve a great range of hydrau-lic installation conditions and gradients. If requested Bento-fix® coated, the GCL with an ad-ditional polymer sheet, will help to improve the performance.The magic of bentonite: The unmatched swelling cha-racteristics of bentonite make

it seem like amagic product.When hydratedand permeatedunder confine-ment with freshwater the ben-tonite layerswells andforms a gel-likelow permeablebarrier. A uni-form layer ofp o w d e r e dsodium ben-tonite encapsu-lated betweengeosynthetics

and thermally locked with nee-dle-punched, nonwoven staple fi-bres does not even need muchwater to hydrate. It can absorbthe water content of soil. In casesof accidental puncture of the theGCL, the bentonite will swell tofill the puncture or swell around

and seal any object that has be-come lodged in the bentonitelayer. In long-term applications,even where desiccation can occur,the high-grade bentonite ofBentofix® maintains its strongswelling capacity and can rehy-drate to repair micro-cracks thatmay have developed. It sounds likemagic but it is the bentonite inBentofix®.

Chemical compatibility:In combining synthetic and nat-ural materials, geosynthetic clayliners provide a versatile, highlyengineered solution for a largerange of liquid containment applications and environments.From landfill caps to river em-bankments, and environmentalprotection beneath roads/rails tosecondary containment beneathfuel tank farms, the range of hy-draulic barrier scenarios solvedby Bentofix® is significant. Undernormal stresses and hydrated ini-tially with fresh water, the ben-tonite in GCLs will establish anoutstanding, long-lasting, con-sistent barrier against liquids ofvarying concentrations of con-taminations. Also, the availabilityof different types of Bentofix®,such as the use of a polymercoating on one side of the GCLand the needle-punched nonwo-ven fibres on the other, and theuse of composite system designswith other geosynthetics enablesdesign specific adaptations to ensure proper performance with-in differing chemical environ-ments.

Bentofix® IQHydraulic

»Bentonite and water: the capacity for greatness.«

Fig. 1Hydraulicconducti-

vity in correla-tion to

confiningstress.

The IQ of Technics: Excellent hydraulic barrier, high shear performance, robust components, durable geosynthetics

Mechanical ProtectionThe quality of a geosynthetic clayliner is proven first in the testing ofits components in controlled labo-ratories. The methods of verifyingthe quality of components and themethods used to manufacture andtest the finished products providestrong support for how materialswill perform. Effective GCL perfor-mance depends on much more thanthe uniformity of the bentonite encapsulated between the geotex-tile cover and carrier layers. Eachpiece of the product, down to the fibres used in the needle-punchingprocess, must be carefully selectedand vetted in order to provide truemechanical protection. This is anarea in which Bentofix® excels.

Needle-punching:The needle-punch method of manu-facturing was invented by NAUE inthe late 1980s. The process bondsthe central, uniform layer of ben-tonite and the outer geotextile layerwith the strength of more than twomillion needle-punched nonwovenfibres per square metre. This ben-tonite fibre reinforcement and en-capsulation across the entire surfaceof Bentofix® panels revolutionisedthe GCL field. The process trans-ferred shear stresses to the geotex-tile layer and resulted in extraordi-nary shear strengths that expandedthe range of GCL applications. Andmost of all the shear strength trans-

fer within Bentofix® is directionallyindependent and uniform in all directions.Peel bond:As composite materials, the compo-nents of geosynthetic clay liners

must be firmly bonded in ways thatensure their performance as a singlematerial. Resistance to peel is es-sential, as the layers are designed to work together. Tensile and peeltesting confirms the strength andsecurity of the bond. NAUE’s tech-nical experts have developed a cor-relation between the standard peeltest and the internal shear strengthof Bentofix®, to provide further confidence and understanding ofthe specification and proper use ofGCLs. Peel strength values are mucheasier to determine than the stan-dard shear test and give a first in-dication of the shear performance.One of the chief ways in which theinternal strength of Bentofix® is en-sured is through the needle-punch

method of manufacturing, whichprovides a firm lock between thegeotextile outer layer and the ben-tonite core. In the field, as shearforces are applied in the soil andthe bentonite hydrates, the bondbetween the Bentofix® componentswill hold and last for the designedpurpose. A project-specific analy-sis, including direct shear testing,should also be performed, to con-firm slope stability calculations.

Thermal Lock: The Thermal Lock Process is a pro-prietary heat-treating process usedto modify and more permanentlylock into place the needle-punchedfibres. Properties of Thermal Lockand needle-punching include in-creased fibre pull-out resistance,higher internal shear values, excel-lent interface friction values andsecured long-term creep resistancefor steep slope applications. Theapplication of heat in combinationwith the needle-punching of syn-thetic fibres creates a perfect bond-ing between the needle-punchedfibres and the carrier geotextile.They provide significant resistance

to pull out and, thus, creep. Advan-ces like this in the production ofBentofix® have helped to achievelong-term shear resistance charac-teristics that significantly outper-form traditional compacted clay liners in critical slope and capping applications.

Puncture resistance:The bentonite used in Bentofix®is also known for its sealing char-acteristics. The powdered sodiumbentonite of Bentofix® swells im-mediately in contact with fresh water and acts as a barrier. Addi-tionally the sealing quality pro-vides an important protection inthe event that a GCL role is han-dled poorly on site and somehowpunctured. The bentonite will swellaround the object and maintain an effective barrier. However, morethan the bentonite comes intoplay. The robust, synthetic fibresthat are needle-punched across the surface of Bentofix® and thescrim-reinforcement standard withBentofix® rolls provide additio-nal, high-quality resistance topuncture.

»They who test and knowhow to test, they are wise.Follow them.«

Bentofix® IQMechanical

Fig. 2Minimum expec-ted shear stresscorrelated fromBentofix® peelvalues differen-tiated into threeconfining stresscategories.

The IQ of Quality: High-swelling bentonite, quality-controlled components, superior manufacturing method, years of research experience

Physical StabilityThe physical stability of geo-synthetic clay liner designs is strongly dependent upon appropriate matching of thespecified GCL to the site char-acteristics, such as the type ofliquid that may hydrate thebentonite core, slope angles,soil types and potential pointsof interface between the GCLand other types of geosynthe-tics and soils. Of chief inter-est is the GCL’s resistance to creep and shear forces. Also of consideration is the inter-face strength of the GCL. The needle-punched nonwovenstandard in the production ofBentofix® provides an answerfor all of these concerns.

Creep resistance:Because of NAUE’s history ofnonwovens manufacturing, in-stead of using another com-pany’s nonwoven geotextileNAUE selects the individual, especially for Bentofix®,devel-oped, nonwoven staple fibres

used to manufacture the non-woven layers of Bentofix® GCLs.NAUE has even developed specialneedles and needle-board pat-terns to maximize the in-terlocking effect of all layers, to perfectly encapsulate the sealing bentonite core and ensure high internal shearstrength. In combination withthe proprietary Thermal Lockmethod which further secures thefibres, a key level of performanceresults in the field. The internalshear resistance of Bentofix® develops as the shear stress istransferred to the nonwoven sur-face. The pull-out of the individ-ual fibres across the surface isstrongly reduced. Without thatstrength in the fibre layer, the

bentonite would be at risk formigration, which in turn couldlead to shear failures as resist-ance diminishes. The thermallyfixed, staple fibre matrix ensureslong-term, dependable perform-ance with high shear strengthand resistance to creep.

Shear strength:The importance of good inter-nal shear strength cannot beoverstated. Shear strength iswhat makes a Bentofix® GCLsafe and suitable for installa-tion along slopes, such as in

landfill caps and levee em-bankments. While the ben-tonite encapsulated in Bento-fix® possesses extraordinaryswelling characteristics and isan outstanding barrier, bento-nite itself has very poor shearstrength after hydration. With-

out the geosynthetic encapsu-lation and protection, evenhigh-quality bentonite wouldnot perform as well as thickertraditional clay. But bondingtogether powdered sodium bentonite and the cover non-woven geotextile fibres in

NAUE’s needle-punch methodtransfers shear forces from thebentonite to the carrier geo-textile, which is designed to resist them. This largely eli-minates failure concerns with the core, leaving only the outer

layers of Bentofix® and thesubsequent interfaces withsoils/geosynthetics to be ad-dressed.

Interface friction:The frictional properties of ageosynthetic clay liner panel

are of great signifi-cance, particularly inregards to slopes indesigns. Nonwovengeotextile outer lay-ers, or a nonwovengeotextile on oneside and a slit-filmwoven geotextile orother suitable geo-synthetic on the otherside, allow the in-crease of the inter-face friction angle. Insystems with a struc-tured geomembrane,

for example, the interface fric-tion (and the stability of thedesign) is exceptional, as thenonwoven fibres interlock withthe textured surface. The non-woven outer layer on Bentofix®GCLs also provides exceptio-nal interface friction with soils.

Bentofix® IQPhysical

»Time creeps along, but Bentofix® won’t creep

with time«

Fig. 3Creep performance

of a Bentofix®GCL (permanent

hydrated con-ditions; 30 kN/m² confining stress;

inclination of 25°).

The IQ of Applications: Resists high water heads, ideal environmental protection, ideal barrier for landfills, versatile sealing applications

Geosynthetics are engineered forparticular functions, and variationson product classes address theneeds of particular applications.Though the quality of the raw ma-terials and the advanced manufac-turing methods used to produce theend products needs to be under-stood and stressed, material dura-bility is what really matters in the final judgement of any application.For geosynthetic clay liners, withtheir high-swelling capacity yet sensitive bentonite cores, durabilityis even more important. Bentofix®

GCLs are engineered with thestrength-enhancing safeguardsand confirmed with the stringenttesting regimes necessary for as-surance and long-term performance.

Long-term resistance:The use of needle-punched fibre re-inforcement across GCL panels has,without question, changed and im-proved the field. Nonwoven, staplefibres have become the preferredcomponent of the cover layer geo-

textile for bentonite security, punc-ture protection, increased interfacefriction, just to mention a few advantages. But what many do not realize is that the nonwoven

geotextile’s performance is highly,but not only, dependent upon thelong-term oxidation resistance ofthe individual synthetic fibres inthe nonwoven layer. During produc-

tion of Bentofix®,NAUE puts these fibres through extensive testing (fibre strength,elongation and HALS additivepackage) to ensure strength andoxidative resistance.

Peel/Shear correlation:Geosynthetic clay liners are com-posite materials. Therefore the riskof product components separationmust be eliminated. The adventof needle-punched nonwoven re-

inforcement fibres across GCL pan-els went a long way towards thisgoal, in that it transferred theshear strength responsibility fromthe low shear strength bentonite

to the high shear strength of thenonwoven geotextile while lock-ing them together. Confirmingthat shear strength with testingrequires a significant amount of

time. To help thefield improve itsunderstanding ofGCL durability,NAUEdeveloped the keycorrelation betweenshort-term peeltests and long-termshear results. Theconfidence inspiredby this innovation,which was also con-firmed in long-termstudies, led to manyGCL applications alot of them evenwith approvals.

Stability against erosion and piping:If the bentonite is poorly encapsu-lated, high water pressure can in-duce bentonite particles to migrate.The Bentofix® fibre reinforcementholds the bentonite powder latterlyin place under confining or hydrau-lic pressure. This way the uniformbentonite distribution is main-tained. Under high hydraulic gra-dients there might be a risk thatunder high water heads and coarse

subgrades bentonite could migrateout of the GCL. Together with thedense needle-punching, the Ther-mal Lock process and either ascrim reinforced nonwoven geotex-

tile carrier layer or a firm slit-filmwoven, Bentofix® GCLs show astrong resistance against possiblepiping effects. This process pro-vides a high-strength, durable matrix of staple fibres that resists fibre pull-out and, thus, protectsand restrains the bentonite. In the lab and in the field, Bentofix®performs.

Field performance:The needle-punched nonwoven carrier geotextile provides excep-tional puncture protection, shearstrength and frictional character-istics. The scrim reinforcementguards against installation dam-age and panel shrinkage from acci-dental, early hydration. The uni-form layer of powdered sodiumbentonite provides immediate, void-free swelling and outstanding barrier performance. And the sec-ondary geosynthetic outer layer,whether nonwoven, woven or onethat uses a special polymer coat-ing, provides application or site-specific qualities to ensure long-term stability against erosion. All of this has been tested, even underlong-term conditions.

»After all is said and done, quality anddurability are what really matter«

Bentofix® IQDurability

Fig. 4Precipita-tion, drai-

nage run-offand permea-tion valuesof GCLs un-

der 1 m coversoil in Ger-

man climate.

The IQ of Ecology: Reduced energy costs in production, long-lasting designs, low transportation costs; reducing carbon footprint

Bentofix® Thermal Lock geosynthetic clay liners (GCLs) are needle-punched, reinforced composites that combine two durable geo-textile outer layers and a uniform core of high-swelling powder sodium bentonite clay. This construction forms a shear-resistant hydraulic barrier with self-sealing characteristics. When hydrated with fresh water, the bentonite swells and forms a low per-meability gel layer, the hydraulic performance of which is equal to or better than traditional, thick compacted clay liners.

Additionally, the proprietary heat-treating process – Thermal Lock – permanently locks the needle-punched fibres, increases the pull-out resistance of the fibres and ensures long-term shear resistance. Bentofix® GCLs are impregnated with a 500 mm wide, uniform layerof bentonite in both longitudinal directions. This enables an immediately sealed overlap without the need for further bentonite ad-dition on site. Bentofix® BFG is also impregnated with an additional, uniform layer of sodium bentonite powder across its nonwovensurface. This advance is ideally suited for pond and waterproofing applications, since the outer layer of the nonwoven geotextile creates an intimate contact zone in overlap areas, such as with concrete surfaces.

Bentofix® GCLs are part of an important trend toward the combined use of geosynthetics and clay materials in barrier applications as a stand-alone liner system and in the synergistic use of GCLs and geomembranes to maximise liner system efficiency.Bentofix® Thermal Lock GCLs are utilized in but not limited to the following applications: landfill caps and lin-ers; environmental protection under roads, railways, and airports; dam and dyke sealing;vertical barriers; ponds; waterproofing; and secondary containment.

NAUE’s most recent GCL development, Bentofix® X, exemplifieshow modifications to GCL product design can be made to anticipatethe special challenges of a particular site. Bentofix® X is a polyolefinpolymer-coated GCL. The woven fabric is coated with a low-permeabilitypolymeric polyolefin coating to achieve an immediate barrier prior to hy-dration. Bentofix® X is an advance for GCLs in some specific applications, suchas waterproofing, oil and gas tank farms, landfill capping and cover systems orwhere high hydraulic gradients are present.

The information contained herein is the best to our knowledge, true and accurate. There is no implied or expressed warranty.© 2011 by NAUE GmbH & Co. KG, Espelkamp-Fiestel, Germany · All rights reserved. · Status 11.02.2011

®

and Bentofix® are registered trademarks of NAUE GmbH & Co. KG.

NAUE GmbH & Co. KGGewerbestrasse 232339 Espelkamp-FiestelGermany

Phone +49 5743 41-0Fax +49 5743 41-240E-Mail info@naue.comInternet www.naue.com

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