The fiberglass geogrid geomaterial is used for the asphalt overlay in the widening and reconstruction of the old cement concrete pavement, which can effectively prevent reflection cracks and improve the quality of the pavement. Combined with specific projects, this paper introduces its implementation plan, construction method and application effect.
1. Overview
The cement concrete pavement in Qiqihar City was built in the 1960s, and most of them were built in the 1980s and 1990s. At present, some of them have exceeded the designed service life, and some other pavements have not exceeded their service life, but with the rapid increase of traffic volume in recent years, the concrete pavement has been damaged to varying degrees. At the same time, with the opening of our city to the outside world in recent years, the reconstruction of urban infrastructure has been intensified, and the widening and reconstruction of the original old cement concrete pavement has become a real problem. In the reconstruction and expansion of Nanma Road in 1998, the original 14 m wide old concrete pavement was converted into a 21 m wide asphalt concrete pavement. At that time, only the old cement concrete pavement was repaired with asphalt gravel, and then paved with a 4 cm medium-grain asphalt concrete surface. In 1999, the same method was used in the reconstruction of the cement concrete pavement around the stadium. After several years of traffic operation, we found that most of the original structural joints of the old concrete pavement were reflected, and the widened joints formed through joints along the road. Some cracks cause asphalt concrete to fall off under the action of vehicle load,
Its damage can only be maintained and repaired, which not only affects the traffic operation, but also seriously affects the service life of the road and the road landscape. To this end, in 2000 we
In the reconstruction of the old concrete pavement of Huxi Road and Zhonghua South Road in 2008, glass fiber geogrid was used for construction.
2. The current situation of Huxi Road and Zhonghua South Road
Both roads were built in 1987, with a width of 7 m. At that time, the design strength was designed according to the compressive strength of No. 30, using 70% gravel and 30% crushed stone as the main aggregate, and the expansion joint spacing was 45 m; There are different degrees of damage in use; there are few broken plates, mainly because the longitudinal seam and the shrinkage seam are seriously gnawed, especially the original expansion seam is too close, and the damage is the most prominent. Based on actual investigation and analysis, we believe that:
(1) The original design standard is low;
(2) The current traffic flow increases and the road surface is narrow;
(3) The spacing of expansion joints should be increased;
(4) The overall strength of the original concrete pavement is good.
Based on the above reasons, we would like to use glass fiber geogrid reinforcement materials in the reconstruction of Huxi Road and Zhonghua South Road, summarize and explore new ways of reconstructing old cement concrete pavements that are suitable for our city's natural conditions and characteristics, so as to help our city rebuild many of the previously built roads in the future. Cement concrete pavement provides practical experience.
3. Implementation scheme of overlay on old cement concrete pavement
We designed 4 schemes for implementation on two roads to sum up experience. The asphalt concrete overlay structure used in the old cement concrete pavement is as follows:
(1) 4 cm medium-grain asphalt concrete + single-layer glass fiber grid + 6 cm coarse-grain asphalt soil + treated concrete slab;
(2) 4 cm medium-grain asphalt concrete + single-layer glass fiber grid + 6 cm coarse-grained asphalt concrete + single-layer glass fiber grid + 3 cm
Fine-grained asphalt concrete repairing road arch + treated concrete slab;
(3) 4 cm medium-grain asphalt concrete + single-layer fiberglass grid + treated concrete slab;
(4) 4 cm medium-grain asphalt concrete + 6 cm coarse-grain asphalt concrete + treated concrete slab.
Treatment of old cement concrete slabs: (1) Cut off the severely damaged ones, and make up for the concrete with the same label as the original concrete to form a consistent strength. (2) For the structural joints, the debris should be cleaned, the concrete pavement should be cleaned, and asphalt or tar sand should be poured into the structural joints.
4. Characteristics of glass fiber geogrid
Fiberglass geogrid is a new type of excellent soil-based material to enhance the performance of road pavement. The main component of glass fiber is silicate, which is a material with extremely stable physical and chemical properties. It has high heat resistance and excellent cold resistance (general working temperature is -100 ℃ ~ 280 ℃), high strength, high modulus, good chemical stability, corrosion resistance, low expansion coefficient, good dimensional stability. The use of fiberglass geogrid can effectively improve the force distribution of the pavement structure by using its excellent characteristics, and can effectively prevent and reduce reflection cracks, thereby improving the quality of the pavement and prolonging the service life of the pavement. This time, the glass fiber grid G101122 is selected.
5. Construction methods and requirements
(1) Evaluate the bearing capacity of the old cement concrete pavement. If the bearing capacity is insufficient and cannot meet the overall strength standard, it will be dealt with. The joints and cracks of the cement concrete pavement should be cleaned and filled in advance. to keep the surface in good condition.
(2) In order to keep the glass fiber grid well bonded to the original road surface and meet the operating requirements of the asphalt concrete paver, it is necessary to pour adhesive layer asphalt on the original road surface, or lay the glass fiber grid first, and then pour it Adhesive layer asphalt, and then evenly sprinkle some fine-grained stone chips on the glass fiber grid,
Then use a light rubber wheel roller to do moderate rolling on it.
(3) After the fiberglass grille is laid, the vehicles should be strictly controlled to drive on it and it is strictly forbidden for the vehicle to turn and brake suddenly on it, so as to prevent damage or damage to the fiberglass grille.
(4) When asphalt concrete is paved, metal components such as the leveling trolley of the paver should be prevented from damaging the paved fiberglass geogrid.
6. Observation of the current situation of road use
The construction of Huxi Road and Zhonghua South Road started on May 15 and was completed and opened to traffic on September 25 of that year. In the process of use, observations are made once a month. After two years of operation, the results displayed by each road section are obviously different. In the road section where no fiberglass grille is placed, after a winter,
Reflective cracks appeared in the spring of the following year, and over time, almost all the structural cracks of the old cement concrete pavement were reflected. There are also differences in the use of fiberglass geogrid sections. That is to say, no reflection cracks have appeared in the thicker road sections of asphalt concrete cover so far, while some small reflection cracks have been found in the thinner cover road sections. Especially at the widened longitudinal joints, the glass fiber grid forms obvious cracks, while no cracks are formed at the widened longitudinal seams with double-layer glass fiber grids. It can be seen that the application of glass fiber geogrid geomaterials has a good effect in widening and reconstructing the old cement concrete road cover. This experimental application provides valuable experience for future road reconstruction in our city.
7. Conclusion
A comprehensive investigation and data analysis of the original roads of these two roads show that the original and old cement concrete pavement has uniform strength and strict treatment of structural joints before the cover. We believe that:
(1) When the thickness of the cover is greater than 12 cm, the original cement concrete pavement has no reflection cracks, so the thickness of the cover should not be too thin.
(2) Double-layer glass fiber geogrid should be used at the longitudinal connection of the old road widening, so that the effect is better.
(3) It is particularly critical to find and repair road arches for old cement concrete pavements, so that the glass fiber grid is laid flat, ensuring uniform stress, and exerting the excellent performance of the glass fiber grid.
