1 highway environmental protection and maintenance is the need of social development.
The Fifth Plenary Session of the 18th CPC Central Committee put forward green development. We should adhere to the basic national policy of saving resources and protecting the environment, accelerate the construction of a resource-saving and environment-friendly society, comprehensively save and efficiently use resources, establish the concept of saving and intensive recycling, strengthen environmental governance, implement the strictest environmental protection system with improving environmental quality as the core, and solidly promote ecological environmental protection, so that a good ecological environment can become the growth point of people's quality of life and the power point to show China's good image.
Highway maintenance must conform to the country's major policies and development strategies, implement resource conservation and environmental protection, and realize the concept of green highway maintenance. We highway people should study the application of new materials and technologies on the premise of saving highway building materials, recycling, reducing the emission of toxic and harmful substances and reducing the carbon emission of maintenance projects, so as to maintain the highway well and serve the people.
2 recycling is a powerful measure to save resources
2. 1 Old pavement materials become subbase or base course of pavement through regeneration.
20 14, 20 15, Baiyin highway administration made full use of cold recycling technology in the maintenance project of 60km of 109 national highway, used cement as recycling agent, milled and planed the old road 22cm, and proportionally added 15%-20% crushed stone (specification 20-0. Then, according to the water content of the milling material, appropriate amount of water is added to make it reach the optimal water content, and leveling and compaction are used as the subbase of the pavement. This construction scheme and technology make full use of the original road waste, reduce environmental pollution, save cost150,000, and achieve a win-win effect.
2.2 Semi-flexible base has broad application prospects.
Semi-flexible base has been widely used in Zhejiang, Shanghai, Hainan, Jilin and other places. Through their own practical experience and theoretical research, the right amount of gravel, foamed asphalt, cement, etc. It is added to the milling and planing materials of the old pavement, then spread on the base and under the pavement, and rolled to form a semi-flexible base. This semi-flexible base has high strength, and its strength increases with time. It has good high temperature stability, water stability and low temperature resistance.
With the increase of service life of pavement in expressway, Gansu Province, the number of resurfaced sections has also increased year by year. Continue to use the resurfacing mode in previous years, milling the pavement completely before resurfacing, which takes a long time and costs a lot. If recycling technology is adopted, a certain amount of foamed asphalt, cement and crushed stone are added in the milling process of cold recycling equipment, and then the original asphalt pavement is turned into a semi-flexible base in situ, and then the surface is covered with 5cm SMA. This scheme not only makes full use of the old pavement materials, but also reduces the environmental pollution and carbon emission during the mixing process, which greatly saves the transportation and material costs. The semi-flexible base slows down the reflection cracks of the semi-rigid base, and has high strength and good durability in the later stage.
Up to now, Baiyin Levin Center, Lanzhou Levin Center and other high-tech centers in the province have a large number of milling materials in stock. If all these milling materials are used in the secondary road reconstruction project and used as semi-flexible base, it is a win-win scheme.
3 whether the effect of micro-surfacing meets the requirements of environmental protection
Micro-surfacing is a kind of thin layer with high skid resistance and durability, which uses special mechanical equipment to mix polymer modified emulsified asphalt, coarse and fine aggregate, filler, water and additives into slurry mixture according to the design ratio, and spreads it on the original road surface.
Through the analysis of the production formula of emulsified asphalt for micro-surfacing, in the production process of emulsified asphalt, according to the different solid content, different doses of emulsifier are added, and hydrochloric acid (about 3.5%) in the same proportion as emulsifier is added. Hydrochloric acid is volatile and its function is to accelerate the demulsification of emulsified asphalt. Most of hydrochloric acid volatilizes into the air, and a small part is wrapped in asphalt, so it is not easy to release and volatilize. Non-volatile residual hydrochloric acid is diluted by rain when it rains, and volatile hydrochloric acid will also cause serious pollution to the atmosphere.
From 20 12 to 20 15, through the investigation of bridges and drainage structures for four years, it is found that concrete is corroded as long as there are beam ends, slab joints, expansion joints and drainage holes. And through the investigation of the bridge bottoms of Baiyin West Link Bridge, Xiangquan Link Bridge Wangjiashan Exit Bridge and 109 Line, it is found that there are only obvious traces of running water in the places where water seepage occurs on the bridge deck and expansion joints, which does not cause corrosion of beam and slab concrete. The analysis of the causes of beam and slab corrosion shows that the only difference is that micro-surfacing is done on expressway, but the connecting line and 109 national highway are not. Obviously, the residual hydrochloric acid will corrode the structure.
Highway greening construction is the focus of environmental protection
Highway construction and maintenance must attach importance to nature protection and ecological environment construction. A well-designed expressway should be naturally and harmoniously integrated with the surrounding ecological environment. Through greening, the natural environment can be protected, the road capacity can be beautified, the air can be purified, the CO2 in the tail gas can be absorbed, and the noise can be reduced.
Highway greening construction should follow the basic requirements, adjust measures to local conditions, adapt the land to trees, consider the local climate, soil and land types, and choose tree species, lawns and ground cover plants with strong drought resistance, salt tolerance and ornamental value according to the principle of adapting the land to trees, which can not only adapt to the local land conditions, but also meet the requirements of highway greening, such as K 1425+000 in expressway, Bai Liu.
Highway greening construction should also meet safety requirements. Low trees or shrubs should be selected in the central median to prevent glare without affecting the driver's sight, and a safe distance must be left at the corner of the intersection.
In the greening of the interchange area, landscaping is the main way to highlight local characteristics, such as the greening in the ramp enclosure of Baiyin West Exit of Bailan Expressway, with weeping willows and evergreen shrubs as the center and some Chinese roses, ginkgo trees and peach trees cleverly dotted around. Clover is planted in all the land to form a green carpet, and the landscape is composed of geometric curves with large color blocks, which makes the curve of interchange ramp harmonious with the environment and the landscape open and concise.
Slope greening is mainly to prevent water erosion and wind erosion, protect subgrade, reduce noise, absorb harmful gases and create a beautiful driving environment. According to the investigation of road conditions, arch skeleton and hexagonal precast blocks are the main subgrade protection methods in some sections of expressway, Bai Liu. Due to poor soil quality, low fertility, drought and other reasons, so far, the slope vegetation protection in many sections has not been formed, resulting in the lack of soil inside the skeleton and the bare arch skeleton. There is an urgent need to cultivate seedlings in the skeleton, and drought-tolerant and salt-tolerant grass and tree species are needed. Vegetation with strong sand-fixing ability covers the exposed slope and protects the subgrade.
During the construction period, highway greening is only reasonable planting grass and trees, and the key lies in the later maintenance and management. Highway greening land has low fertility and water shortage, making it difficult for plants to grow. Therefore, it is necessary to strengthen the post-cultivation management of greening plants, timely fertilize and water, and add water diversion irrigation facilities. Plants should be trimmed in time and carefully. Pruning can improve the ventilation and light transmission conditions of trees, remove branches of pests and diseases, and make trees flourish. Dig out the dry trunk in time and plant suitable trees and flowers.
5 conclusion
Highway maintenance strategy must adhere to the basic national policy of saving resources and protecting ecological environment, and do a good job in highway greening construction. Road maintenance is like a doctor's treatment. We should not only consider the treatment, but also consider the degree of damage to other organs caused by the side effects of drugs. We serve the society on the premise of saving resources and protecting the environment.
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