Geotextile Installation Guide
Before installing geotextile for road stabilization, it is better to get more familiar with road construction and the difference between concrete asphalt and bitumen asphalt and the structure of geotextile in the construction of roads, it should be paid attention to some factors such as water infiltration, groundwater, canals and infrastructure under the road, ambient temperature, and the contraction and expansion of asphalt in different seasons, and so on.
Installation of geotextiles in coastal protection, tunnel isolation, dam construction, protection of geomembranes in places where geomembranes are used and in road construction that is our subject. Geotextiles do not decompose due to being polymeric in the soil, and because they have the ability to protect, split, filter, reinforce, or discharge, they can be used for a variety of road construction tasks, including improving coating performance and increasing The useful life of asphalt and road and the usage of this fabric reduces the volume of asphalt height by at least 30%.
Learn more : Geotextile Zarif Mosavar Industrial Group.
the Reasons of Geotextile Installation in Road Stabilization
- Geotextile filtration mechanism
- Geotextile separation mechanism
- Strengthening the effect of geotextile and protection of asphalt
Geotextile filtration mechanism
is used for filtering Coarse from gravel or utilized in drainage and water conduction.
Not every type of geotextile performs the desired filtration function. An effective fabric should have a large number of openings with a fixed size woven into the fabric. Most of nonwoven fabrics have this standard. The filter cloth should not trap particles inside the pores and should not change during the discharge of porosity under loads.
For proper design of the drainage system, local conditions such as soil characteristics, external loads imposed on the system (static or dynamic) and the prevailing hydraulic conditions must be evaluated.
Geotextile separation mechanism
Installation of geotextile as a separation fabric is a barrier for separation between the surface and the substrate layer.
Strengthening the effect of geotextile and protection of asphalt
Since geotextile has a significant tensile strength, so geotextile layers can be used to strengthen asphalt and make the road more flexible and cause minimal cracking.
Geotextile installation steps for road stabilization
The method of installing geotextiles and geosynthetics for fixing roads with bitumen or concrete asphalt is slightly different, but in general, the implementation method includes the following steps:
- Surface preparation
- Ingredients of road structure
- Terms and distribution of Tack Coat
- Geotextile Installation
- Tightening geotextile fabric
- Final asphalt
1. Surface preparation
To improve the quality and longer life of roads, the surface should be as smooth as possible and free of aggregates and contaminants such as oil and water before spreading the geotextile. Cracks more than 5 mm wide should be filled with bitumen. Larger cavities and cracks should be filled with a suitable hot or cold asphalt mixture.
2. Ingredients of road structure
The topsoil is removed and the subgrade is compacted. Then 600 mm of embankment is done using local materials. Compression is performed up to a height of 150 mm.
Recommended primer: Most of the suitable primers used are 170 grade bitumen with a cut of 10 to 20%.
Lining application: The primer is applied directly on the compacted embankment, which is done by ordinary spreading units.
3. Terms and distribution of Tack Coat
Single coat (coated asphalt) is a hot liquid that is used to saturate the geotextile for waterproofing and attach it to the old coating. Experience has shown that the best connection is achieved using a single grade 170 bitumen coat class. Pure bitumen rapidly increases the bonding strength and allows the geotextile to be in place quickly in the installation of the geotextile.
Required volume of single coat: Excess or insufficient volume of single coat can cause the new cover to be moved or laminated. The single coat material should extend about 5 to 7 cm more than the edges of the geotextile. The single coat should be placed between all overlaps. Depending on the roughness of the road, the porosity of the old pavement, the use or non-application of the leveling layer and the absorption rate of geotextile bitumen, between / 9. Up to 1.2 liters per square meter of single coat is required to saturate the geotextile and connect to the surface of the old coating.
Single coat temperature: The allowable temperature for a single coat is between 143 and 162 degrees Celsius (suitable temperature for laying asphalt). The air temperature should be above 10 ° C for good single coat performance.
Spreading single coat: Note that if asphalt is used, in case of rain on the geotextile before laying the asphalt, the geotextile should be allowed to dry completely. In addition, the minimum density of asphalt pavement should not be less than 4 cm. By observing the above, first the binder layer and then the top layer are installed. The most suitable amount of single coat varies between 0.9 to 1.4 liters per square meter of bitumen, which depends on the condition of the existing road and the type of geotextile selected.
When installing a geotextile, if a heavier geotextile is selected, more single coat should be applied on it. The single coat should be spread by a calibrated spreading truck and the machine should spread the single coat 150 mm wider than the geotextile. After installing the geotextile, it is sprayed on the geotextile with a coating of Class 170 bitumen. This process can be completed with a roller for flattening. If a re-insulation is required, a layer of Class 170 bitumen is re-applied and continued by leveling. The minimum thickness of dense asphalt pavement should not be less than 4 cm. By observing the above, first the binder layer and then the top layer are installed.
4. Geotextile Installation
Geotextile installation is easy and convenient, for projects less than 200 square meters, geotextile can be spread by hand, basic tools and hand tail. For large projects, a simple roll spreader that displays specific stress control devices and has geotextile smoothing presses is recommended. The device can be easily installed on an excavator or in front of a loader and spreads rolls up to 250 kg, resulting in minimal deviation in the path of a wrinkle-free installation. Wrinkles larger than 25 mm should be removed. If the road is wide and the geotextile roll is used side by side, it should be at least 150 mm overlap.
When the geotextile is spread by hand, the lengths of approximately 10 m should be opened and smoothed and placed on the surface before being applied to a single coat in contact with. Brushing should start from the center and go out in two directions. The coat is then spread and the geotextile must be pressed four times with a roller to create a good adhesion to the existing surface.
5. Tightening geotextile fabric
After spreading the geotextile fabric on the road and making sure that there are no lumps under the fabric and the edges overlap, you can fasten the fabric to the bottom in three ways:
- use sewing
- use adhesives
- use nails
- Hot Air-Blowing
6. Final asphalt
After leveling and penetrating coating (priming) and surface coating (single coating) and spreading the geotextile fabric, it is the turn of asphalt spreading, which is done in different approaches such as spreading with grader, spreading with paver, and then using metal and rubber rollers. The asphalt is compacted and after the final tests, the road is ready for operation.
Geotextile installation plays an important role in the construction of highways. They are used effectively in almost all new constructions. It greatly increases the service life of the pavement and effectively reduces maintenance costs. This significantly separates the substrate from the subsoil and provides structural strength due to its high resistance to deformation. It also reduces the thickness of the granule period below the base. If geotextiles are used in highway construction, it will be useful because its use reduces the initial costs of construction and frequent road maintenance