The properties of cold recycled materials are different from those of traditional road materials, so the requirements for forming are also different. Cold recycled materials can be roughly divided into two categories according to regenerants: inorganic regenerants and asphalt regenerants. When asphalt is regenerated, a small amount of cement is often added to improve its water damage resistance. The commonly used inorganic regenerant is cement, and others include lime fly ash, cement fly ash, etc. Inorganic stable cold regeneration is generally formed and cured according to traditional semi-rigid materials. Carry out heavy compaction test or vibration compaction test at room temperature, and keep in good condition at 20 ℃ or 25 ℃ for 7 days. The water content is determined by the water content strength relationship. The situation of cold regeneration of asphalt stabilizer is complex, and there is no unified method. The Marshall method is a common method to determine the cold cracking strength or the dry cracking strength of recycled asphalt.
The United States issued a questionnaire survey on regenerants to 52 Local highway management agencies across the country. 46 replies, 24 frequently used, 13 places used partial * * regeneration, 4 full depth *, 7 both. Emulsified asphalt is used in 24 places, and most of them use high flow emulsified asphalt. Medium setting or slow setting asphalt is partially used. Lime, fly ash and cement are used in 8 / 4 / 3 places respectively. Composite stabilization of asphalt and cement is widely used in cold regeneration in South Africa, and the amount of cement is generally 1%. It is considered that the addition of cement can significantly improve the water stability of cold recycled materials and improve the mechanical properties of materials, especially the early strength. Because China has rich experience in using semi-rigid base course, and many recycled sections use recycled materials as base course, it is common to stabilize with cement, and when stabilizing with cement, the experimental method mainly refers to the semi-rigid material experiment.
Cold recycled pavement structure
The basic structure of cold recycling abroad is: hot mix asphalt mixture layer + cold recycling layer + old base. The old base course is generally gravel base course. At present, the most commonly used structures of domestic cold recycled roads are hot mix asphalt mixture layer + recycled layer + semi-rigid layer and hot mix asphalt mixture layer + recycled layer. With a large number of pavements entering the maintenance period in China, pavement cold recycling technology will be more widely used. This paper summarizes the technical points of regeneration at home and abroad. There is no special evaluation method for pre cold regeneration evaluation in China, which needs further research; Cold recycled materials are generally used as the base layer at first, and are gradually used as the lower layer at present; In the cold recycling construction in China, cement is more used as a recycling agent, and its experimental method has been relatively unified, mainly referring to the traditional semi-rigid materials; However, the experimental method of cold regeneration of asphalt as regeneration agent is not unified, and further research is needed to determine a reasonable experimental method.
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