Roli Jindal DuPont It is well established internationally that the use of geo-textiles enhances the quality and durability of roads.

In the United States there are many government agencies (both state and federal) that mandate the usage of geotextiles in certain applications. The use of silt fence fabrics ( geotextiles) for erosion and sediment control is now required on all earthworks construction project in all 50 states of the US. California mandates the use of geotextiles as underlay, when a small thickness of asphalt (overlay) is applied over an existing roadway. The US Environmental protection agency (EPA) has mandated the use of geosynthetics in landfills for some twenty years. This includes the use of geomembranes for liquid isolation, geotextiles for filtration and drainage, and reinforcement geosythetics, geogrids and fabrics, for slope stability. Virtually all landfills constructed, or closed, in the US utilize geosynthetics. USA – mandates the use of geo-textiles

In India, we need similar awareness and mandation. 2 key points India to adopt correct, application-related specifications Government support to promote use of geotextiles in key road applications

Typical tender specification in India

Inappropriate specification terminology It is common to see, in tender documents, “Apply and Supply of 250 gsm geotextile”. This is meaningless. Reasonable technical requirements of geo-textiles are mainly based on the stresses to which the product is exposed both during installation as well as during the whole life-time of the structure. Relevant parameters for a separation and stabilization geo-textile in road construction tensile strength CBR puncture resistance Elongation, cone drop test, installation damage opening size Specifications on weight and thickness seek to exclude highly engineered membranes that deliver higher performance at lower weight and thickness. Commonly occurring parameters such as “Mullen burst” are not even geo textile specs!

Properties that need to be mentioned in specification - Europe

Understanding the concept of Energy Absorption In road construction, a geotextile is mainly used for separation and stabilization. The corresponding crucial properties are resistance to damage during installation. 95% of the damage usually occurs during installation – mainly during the off- loading of aggregates In the vast majority of cases, if the geotextile survives these installation-related stresses, it will also withstand the in-service stresses. There is a close correlation between the ability of a geotextile to absorb impact energy and its susceptibility to damage during installation.

What is energy absorption The energy absorption potential (W) of a geotextile can be described as the combination of its elongation and its applied strength. It is determined using the stress-strain curve of a geotextile obtained in a tensile strength test. The area under the curve is the energy absorption potential of a geotextile. Typical stress-strain curve of geotextiles according to EN ISO standard

Rutting resistance The regular passage of wheeled transport results into tension stresses that deform the sub- soil. The results of an independent laboratory test indicates a clear relationship between initial modulus and deformation (rutting).

Many European Countries have adopted Energy Absorption as specification Terminology for Road Construction

Specification of the relevant ministry / regulatory body These specifications prescribe minimum requirement for the quality of materials, construction However they usually do not give specific recommendations for specific problems. We need to introduce a clause which makes encourages the usage of geo-textiles. For example : For subgrade treatment and stabilization there are various alternatives – Excavation and replacement of unsuitable soils, providing sand blanket, soil stabilization with lime / cement use of geosynthetics IRC codes do not make any detailed recommendations as to the treatment method. In India, use of geotextiles is neither mandatory, nor recommended, nor encouraged It is one of many “acceptable solutions.” Internationally, codes are very specific about recommending or even mandating the use of geotextiles as the preferred solution.

(a)Notification by the Government : MORTH to issue a notification to various agencies, making use of geotextiles compulsory in roads. Precedent : There is a notification by the Ministry of Environment and Forests, making use of flyash/pond ash compulsory for road embankment construction within a distance of 100km from any thermal power plant. Based on this MoRTH also has issued a letter to various government agencies. (b) Specification of the relevant ministry / regulatory body : MoRTH for road and bridge works, CPCB guidelines, RDSO - needs to be amended. We need to introduce a clause which encourages the usage of geo-textiles – along the lines of European specifications. (c) Codes of practice (e.g. Indian Road Congress, Bureau of Indian Standards, CRRI) need to be upgraded. Indian codes need to drop their ambivalence towards geo-textiles and need to accept internationally proven construction practices. What we request the Government

(d) Inclusion of geotextiles in Central PWD and State PWD manuals and schedule of rates. This will help the state PWD Department to float tenders incorporating the specifications of geo-textiles that have been included in the State Schedule of Rates. What we request the Government (e) Tariff support : Highly engineered geo-textiles are technology intensive. Indian infrastructure deserves the best products available in the world.

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