The geotextile is in the joints and cracks of the old cement concrete pavement, and the new asphalt concrete overlay on the top of the geotextile appears in the corresponding cracks in a short time of use.
In the process of designing flexible pavement structure combination, when paving the surface layer on the semi-rigid base layer, the surface layer of the higher grade road should be thickened appropriately or the geotextile should be laid or other measures should be taken to reduce the reflection cracks.
The geotextiles used on asphalt pavements are mainly geotextiles with superior performance such as glass fiber polyester anti-cracking geotextiles.
Under the action of physical external forces and natural environmental factors (rain, moisture, dust, etc.), the damage to the asphalt surface layer is caused. Adding fine interlayer geotechnical materials (special road anti-cracking geotextile) between the asphalt overlay and the old cement concrete pavement is an effective measure to prevent reflection cracks.
1. Because the temperature shrinkage displacement of the old cement concrete pavement is continuous, the geotextile reduces the bonding force between the surface layer and the base layer. After calculation, after adding the geotextile, the bonding force at the original two-layer interface is significantly reduced, thus making The maximum tensile strain of the cover layer is reduced.
2. As geotextiles have greater extensibility, the displacement of old cement concrete cracks can expand the stress to a wider range through geotextiles, alleviating the stress concentration at the cracks.
3. As the geotextile is soaked with asphalt, it can effectively prevent surface water from infiltrating into the base layer and prevent further deterioration of the base layer.
4. As the geotextile is soaked with asphalt, it can effectively prevent groundwater from penetrating into the human interface and reduce the peeling damage of the asphalt overlay at the reflective cracks.
5. Geotextile interlayer material can slow down the temperature drop of cement concrete slab and reduce the displacement of cement concrete slab.
Geotextile technical requirements analysis
Using geotextile as the interlayer material for the asphalt overlay on the old concrete pavement is an effective measure to prevent reflection cracks. However, the performance of the sandwich material will directly affect the effect of anti-reflective cracks. Some types of geotextiles have obvious anti-reflective cracking effects. The long-term tracking observation and analysis of the used anti-reflective cracking geotextiles, geotextile material properties, and construction methods show that the anti-reflective cracking geotextiles should meet the following technologies Claim.
1. Good temperature resistance. The temperature of the asphalt mixture during hot paving is about 150°C, so it is required that the anti-cracking geotextile material not only cannot melt or soften at this temperature, but also can maintain normal operation. Experience has shown that glass fiber polyester geotextile has the best performance.
2. Good asphalt gum oil adsorption. The normal construction procedure is to spray asphalt glue oil evenly on the cracked pavement first, then pave the fabric interlayer, and then heat the surface layer on it. The hot paving layer should be able to absorb the glue oil under the fabric to make it saturated, so the fabric is required to have good adsorption capacity.
3. Flexible. Flexibility includes two meanings of toughness and surface hardness. Toughness reflects the ability of a fabric to absorb impact energy, and it can be approximately measured as the product of the material's tensile strength and elongation. It is recommended to use the CBR test burst strength R to express its surface hardness, and it is considered that R≥2kN.
4. Good uniformity. The fabric is an anisotropic material. It is recommended that the strength ratio between warp and weft is not more than 1.5 for woven fabrics and not more than 1.2 for non-woven fabrics.
5. Strength requirements. The tensile strength of the fabric should be greater than 400N/5cm, and it has requirements for puncture resistance and burst resistance, and the strength is greater than 800N/5cm.
6. Acid and alkali resistant
7. Strong aging resistance. The anti-cracking geotextile shall maintain a normal working condition within the service life of the road surface.
8. Thickness requirements. In order to prevent the undesirable negative effects of the asphalt overlay after the addition of the anti-cracking geotextile (the overlay is peeled off), the thickness of the geotextile should be strictly limited. According to the experimental analysis, the old cement concrete is added with an asphalt overlay to prevent reflection and cracking , The thickness of the anti-cracking geotextile should be less than 2.0mm.
The application of geosynthetics in this area greatly increases the service life of highways and solves many problems for people.