Application of Glass Fiber Geogrid in Highway Engineering

Reflective cracks are a common phenomenon in asphalt pavement. According to the practice of road engineering at home and abroad, a layer of geotextile is laid between the asphalt surface layer and the intermediate asphalt mixture layer or the coarse asphalt mixture layer, which can be used to eliminate or slow the generation of reflective cracks in the surface layer, thereby extending the road. Service life and reduced maintenance costs. However, since the temperature of the asphalt pavement is as high as 160°C-180°C, the geotextile is wrinkled, deformed and softened, which greatly reduces its performance. It is not only difficult to eliminate or slow down the generation of reflective cracks in the surface layer, but also makes the asphalt pavement more uneven. The unique properties of the fiberglass geogrid fully meet the requirements of asphalt pavement. At present, many projects have used glass fiber geogrid.

When glass fiber is applied to asphalt roads, it can play a role in the following aspects.

(1) Anti-fatigue cracking

The asphalt pavement must have a certain load carrying capacity, and fatigue damage cannot occur within a prescribed time. The asphalt pavement is under pressure in the lower layer that is in direct contact with the wheel. In the area outside the wheel load edge, the surface layer is subjected to tensile force. Because the two stressed regions are subjected to different forces and are close to each other, they are subjected to two At the junction of the force zone, the sudden change of force occurs, and under the action of long-term load, fatigue cracking occurs.

In the asphalt surface layer, the glass fiber geogrid can disperse the above-mentioned compressive stress and tensile stress, and form a buffer zone between the two stress regions, thereby reducing the damage of the asphalt surface layer caused by the sudden change of stress. At the same time, the low elongation of the fiberglass geogrid reduces the amount of deflection of the road surface, ensuring that the road surface will not be excessively deformed.

(2) High temperature resistant rut

Asphalt concrete has rheological properties at high temperature. Under the load of the vehicle, the stress area is sunken. After the vehicle load is removed, the asphalt surface layer cannot be completely restored to its original state, that is, plastic deformation occurs. Under the action of repeated rolling of the vehicle, Plastic deformation continues to accumulate, forming a rut. According to the analysis of the asphalt surface structure, the asphalt concrete under high temperature is subjected to the rolling action of the load, and a slight waveform rheology is formed. There is no skeleton material in the surface layer which can restrain the rheological behavior of the asphalt concrete, resulting in the rheological transformation of the asphalt surface layer. The cumulative stacking, this is the root of the formation of the rut.

The fiberglass geogrid is used in the asphalt surface layer, which plays a skeleton role in the asphalt surface layer. The aggregate in the asphalt concrete penetrates between the grids to form a composite mechanical interlocking system, which restricts the aggregate movement and increases the asphalt surface. The lateral restraint force in the layer, the parts in the asphalt surface layer are mutually restrained, preventing the asphalt surface layer from being displaced, thereby playing a role in resisting the rutting.

(3) Resistance to low temperature cracking

During the severe cold period, the temperature of the asphalt concrete surface layer is close to the temperature, the asphalt concrete encounters cold shrinkage, and tensile stress is generated. Under the repeated action of the load, the tensile stress is further increased. When the tensile stress exceeds the tensile strength of the asphalt concrete, cracks are generated. At both ends of the crack, the tensile stress is more concentrated, and the crack gradually forms a crack, causing disease.

The fiberglass geogrid is placed in the asphalt, so that the tensile strength of the asphalt concrete is greatly improved, and it is enough to resist the large tensile stress without causing road surface damage. Even if micro cracks are generated in the local area, the stress at the crack is concentrated. The transmission of the fiber geogrid disappears and the crack does not develop into a crack.

(4) Delaying reflection cracks

There are two kinds of reflections caused by cracks. One is that after the cracks are formed in the surface layer, the cracks reflect downward, destroy the underlying structure, and reduce the structural strength of the pavement. In the rainy season, water enters the crack and the traffic load (tire pressure) is repeated. Pressure, water creates water pressure in the crack, and the water continuously impacts the asphalt mixture, causing the crack to expand. The other is the original crack in the old surface layer, and the crack generated by the road base layer or the lower road base layer is reflected upward. The new cover road surface cannot withstand the shear force and the tensile stress caused by the movement of the bottom layer, resulting in cracks in the road surface layer.

The fiberglass geogrid interlayer is added in the asphalt overcoat layer to restrain the stress, release the strain, and enhance the overall strength of the asphalt concrete to prevent the crack from being reflected upward or downward.