Geotextiles are creeping in the construction of civil engineering and roads in projects for the environmental protection. The most familiar of geotextiles would be the PET (Polyethylene Terephthalate) geotextiles and the PP (Polypropylene) geotextiles. The two are more or less the same or the comparable, used for the same purposes. Yet there are differences in the material properties, performance and application.
PET Geotextiles
These geotextiles are made from polyethylene tetraphyte fibres, available fabricated as a woven or unwoven fabric. The fibres are strong, durable and resistant to any elongation under load. Good mechanical resistance, high tensile resistance and high durability in severe environment qualifies them for among the best of modern geotextiles.
PP Geotextiles
These geotextiles are spun from polypropylene fibres, and can be manufactured in a woven or nonwoven form. Light, chemical resisting and inexpensive, the geotextiles are widely used in applications covering separation, filtration and drainage where moderate strength characteristics are adequate. These are some of the material properties and performance.
Tensile strength
Perhaps of the greatest comparative feature of the two types of geotextiles would be in their tensile strength. Those made from PET fibres have attained higher tensile resistance and have remarkably lower elongation under load than the PP geotextiles.Also, the PET geotextiles are used in the heaviest duty applications such as reinforced roadways and railway embankments, reinforced retaining walls.While this characteristic of the geotextiles is of value in providing flexibility and convenience in handling and installing them, nevertheless they are not satisfactory for use on projects where a geotextile with a long term capacity is required.
Chemical Resistance
Excellent chemical resistance is exhibited by both types of geotextiles, but they have some differences.Chemical Resistance
Geotextiles made of PET are resistant to acids and alkalis, but long exposure to high concentrations of strong alkalis can attack and degrade the material.
Geotextiles made of PP are resistant to the majority of chemicals including alkalis. Their higher degree of resistance allows them to be used as liner materials in landfills and as drainage materials, as well as for industrial applications.
UV Resistance
The factor of UV resistance is of particular importance for geotextiles that may lie in exposed sunshine for a lengthy period of time prior to being covered with soil. Long term UV stability values of PET geotextiles are better than similar values for PP geotextiles. Mechanical properties of the material will still benefit, although only in a complicated project where the geotextile is covered up but for a temporary length of time.
Geotextiles made of PP will require UV stabilisers to prevent the materials from degrading from exposure to the sun for any longer length of time. Without these additives the PP geotextiles will lose in strength.Water permeability and Filtration
Water permeability (permeability) is another important property of geotextiles. PET geotextiles will generally have smaller-sized pores so that their filtration properties will be more uniform. While these parameters allow for proficient separation of soil layers, water flow is still facilitated. PP geotextiles, usually the non-woven kind, are typically more permeable, enabling expedient draining. They may be utilized in filtration applications in such areas as road subgrades and drainage trenches. They do differ in term of filtration efficiency as a result of thickness of fiber, the method of manufacture, etc.
CBR puncture strength and Durability
Soil is covered with a geotextile that will be aggregate ballast atop.CBR puncture strength is significant for a geotextile that will be punctured by aggregate, etc. PET geotextiles have high CBR puncture resistance which is due to strong bonding of fibres and, lower elongation.Ideal for Reinforcement of Subgrades under Heavy LoadsPP Geotextiles: Puncture Resistant (lower CBR values) as in Light to Medium LoadsApplications like erosion control and temporary roads where traffic loads will hardly affect themInstallationHeavy and dense PET geotextiles will require a little extra handling. But many would argue that their rigidity does tend to make for good alignment, and that they will in fact be easier to lay as the wrinkles will not be formed.Laying and Cutting
PP geotextiles will be lighter, and would require labour to cut and lay such that they can be laid fast over huge area. A more flexible PP geotextile would need coming to anchor properly otherwise it wrinkles and slips off line during laying.
PET geotextile applications
- Reinforcement of highways and railways
- support to retaining walls and embankments
- subgrade support as in Heavy Loads
- for generally heavy duty application over longer period, as in drainage for long lengths, walls, etc.
PP geotextile applications - for fetching out layers road base to separate
- for fetching out liner for landfill and drainage
- for fetching out quick mats on slopes as in erosion control
- also for fetching out use in temporary road as in driveways
Cost Applications
Of course the PET geotextiles will be higher priced based on the fact that there is more tensile strength, the geo products that would stand out. The guess is higher life usage.
PP geotextiles will be coming out quite cheaper and very easy to be generally available. The guess is cheapest available for light duties.
In broad brush, what and how where and why choose
Well, the PET and PP you bet are already well dealt as discussed above and now, who will select what and how
Project load requirement
Environmental exposure
Chemical loading
Budgeted application
Ease of handling in installation
In conclusion
The PET geotextiles and for that matter the PP geotextiles do have their own unique advantages, but the main difference would seem to stand out so far as strength of geottxtile providing major resistance to punctures outstanding!
Which seem to last as well hell of a lot longer too!