In the actual process of cold recycling construction of road base, the main construction materials used include asphalt surface milling material, cement, water, and so on. Usually, when selecting cement, most construction units usually use Portland cement or slag Portland cement due to the consideration of the heat of cementation. This is because such cement contains less heat of cementation and can prevent the occurrence of construction cracks.
Moreover, the construction unit also needs to strictly control the quality of newly added cement and firmly prohibit the use of deteriorated cement. Secondly, the construction unit also needs to ensure that the cement strength truly meets the national standard requirements, whether it is the cement age or stability, which meets the engineering construction requirements. Generally, the initial setting time of cement is around 3-5 hours, and the final setting time is about 6 hours.
In addition, the cold regeneration construction process of road base has high requirements for water use, and the construction unit should try to use drinking water or pure water that is completely free of toxic substances. Furthermore, when selecting milling and planing materials, it is also necessary to ensure the consistency of particle diameter specifications, and it is necessary to effectively combine the needs of engineering construction to select suitable and ideal milling and planing materials. Afterwards, as the main constituent material of the base course mixture, crushed stone should have standardized requirements for its strength, crushing value, etc.
Mix design of cold recycled mixture
The mix design of cold recycled mixture for road base mainly includes three aspects, such as raw material analysis, mix design, and design mix inspection. Follow the "Technical Specifications for Construction of Road and Grassroots in Highway Engineering" to accurately design the mixture ratio and ensure construction quality.
As one of the commonly used technical means in modern highway engineering construction, cold regeneration construction technology has a direct impact on the overall safety and stability of the highway. In order to avoid the occurrence of dangerous hazards, both local management departments and construction enterprises must strengthen the quality control work on the construction site, comprehensively grasp the local geological conditions and natural environmental conditions, Develop standardized construction processes and procedures, adopt advanced construction techniques and techniques, and fundamentally ensure the construction quality of highway engineering.
Based on the milled elevation of the original roadbed, the design elevation of the newly laid base layer of the cold recycled mixture, and the loose paving coefficient determined by the test section, the paving elevation of the newly laid base layer is calculated and the construction setting out operation is carried out.
Smooth road surface
Clean up the debris on the original road surface, clean up the edges, and remove the manhole covers and other structures on the recycled road section. Carry out disease treatment operations such as mud boiling, rutting, and sinking on the original road surface to ensure the smoothness of the original road surface.
Prepare for new feeding
The calculation of the amount of new material added per square meter must strictly follow the average density of the original road regeneration depth. Determine the stacking distance based on the amount of material in each vehicle. When calculating the cement dosage for each square meter of stable layer, it is necessary to strictly follow the cement dosage requirements and determine the vertical and horizontal spacing of cement placement.
Cold regeneration mixing
On the original road surface, the water tanker is driven by the leasing of a cold regeneration machine to move forward. The driving speed is adjusted and controlled appropriately according to the damage situation and regeneration depth of the original road surface. The speed is usually controlled at 6 to 12 meters per minute to ensure that the grading of the milled material does not fluctuate significantly. In sections with severe mesh cracks, the driving speed of the regeneration machine must be effectively reduced, And increase the speed of the milling rotor appropriately. During the operation of the regeneration machine, there must be staff following behind it to check the depth of regeneration at any time. At the same time, the cement content and water content of the mixture should be tested, and adjustments should be coordinated with the regeneration machine staff.
Rolling and shaping
During the initial compaction after the construction of the recycling machine, a steel wheel vibration roller should be used. During the compaction process, high amplitude and low frequency compaction should be used, and the number of compaction passes must meet the compaction degree within the range of 2/3 thickness at the bottom of the recycling layer. The driving speed of steel wheeled rollers must be controlled below 3 kilometers per hour. After completing the initial compaction, the shaping construction can be carried out using a grader.
The grader shall carry out construction on a straight road section in a sequence from both sides to the middle, and in special circumstances, a leveling operation shall also be carried out. The grader shall carry out leveling operations on curved road sections in order from the middle to both sides. The rolling construction should follow the sequence of starting from the edge to the middle, from light to heavy, and from slow to fast, especially for super high road sections, the rolling construction must follow the sequence of starting from the middle to both sides.
Seaming and Turning Treatment
During the process of processing longitudinal joints, construction personnel should reasonably set the width of the road. If there is longitudinal overlap, a full width construction method should be adopted to minimize the overlap and further improve construction efficiency. Moreover, the construction unit also needs to effectively control the time difference between full construction and half construction, which cannot be too long or too short. It is necessary to increase the overlap appropriately according to the construction needs of the project. In addition, when dealing with horizontal turning, the resulting horizontal joints should be treated in advance to avoid downtime.