Section V: Recycling Application of asphalt pavement materials

The recycling application of asphalt pavement materials mainly involves the recycling mechanism of asphalt pavement materials 、 Technical requirements for regenerant 、 Determining factors of mix proportion of recycled asphalt mixture and production process of factory office .

1、 The purpose and significance of regeneration

（1） Regeneration mechanism

Recycling of asphalt pavement materials , The key is the regeneration of asphalt . The regeneration of asphalt is The reverse process of asphalt aging . In aged old asphalt , Adding a certain component Low viscosity oil （ Regenerant ）, Or add asphalt material of appropriate consistency . Recycled asphalt is better than old asphalt Composite fluidity There's a big improvement , The rheological properties are greatly improved .

• The on-site thermal regeneration of old asphalt pavement is to melt the asphalt concrete of friend aging pavement with a combined heating machine , Then use the heated harrowing machine to harrow it loose , Add a certain amount of regenerant and new asphalt , And pave again with a paver 、 RCC , Turn an old road into a new one .

2、 Technical requirements and selection of regenerant

（1） Regenerant action

Regenerant mainly adopts Mineral oil of low viscosity petroleum system , Such as refining lubricating oil Extract oil 、 Lubricating oil 、 Engine oil and Heavy oil etc. , To save money , The engineering contractor can use the wastes of the above-mentioned various oils .

（2） technical requirement

• It has the ability to soften and penetrate , That is, it has appropriate viscosity .
• It has good rheological properties , The flow rate is close to 1, Showing Newtonian fluid properties .
• It has the ability to dissolve and disperse asphaltene , It should be rich in aromatic phenols . Can regenerate effect coefficient K– The wallpaper of ductility of recycled asphalt and ductility of original asphalt represents the ability of old asphalt to restore the performance of original asphalt after adding regenerant .
• High surface tension .
• Must have good heat resistance and weather resistance （ It is measured by the viscosity ratio before and after the test in the test film oven ）.

（3） Technical indicators

Japanese regenerant quality standards also require ： No toxic substances .

3、 Production and application of recycled materials

（1） Mix proportion of recycled mixture

• The mix proportion design of recycled asphalt mixture can adopt Ordinary hot mix asphalt mixture The design method of , Including aggregate grading 、 Determination of various physical and mechanical performance indexes of mixture .
• The selection of regenerant and the determination of its dosage should consider Viscosity of old asphalt 、 Viscosity of recycled asphalt 、 Viscosity of regenerant Other factors .
• The content of old material in recycled asphalt mixture ： For example, it is directly used for pavement surface , The traffic volume is large , Then the old material content is taken as the lower value , Occupy 30%~ 40%; Use high value when the traffic volume is small , The old material content accounts for 50%~ 80%.

（2） Production process

• Recycled asphalt mixture can be produced according to the recycling method 、 Regeneration site 、 The use of mechanical equipment is divided into hot mix 、 Cold mix regeneration technology , artificial 、 Mechanical mixing , Field regeneration 、 Plant mixing regeneration, etc . When the batch mixer is used for mixing , The content of old materials generally does not exceed 30%. When the drum type mixing mechanism is adopted , The old material content can reach 40%~ 80%.
• At present, the method to determine the optimum asphalt content of recycled asphalt mixture is Marshall test method , In principle, the technical standard shall refer to the technical standard of hot mix asphalt mixture .
• The performance test indexes of recycled asphalt mixture include ： Voids 、 Mineral aggregate clearance ratio 、 saturation 、 Marshall stability 、 Stream value etc. .
• The test items of recycled asphalt mixture include Rutting test stability 、 Residual Marshall stability 、 Freeze thaw splitting tensile strength ratio etc. , Its technical standard refers to the hot mix asphalt mixture standard .

（3） The recycled mixture is used in the lower layer of the pavement

On the basis of ensuring the quality of recycled mixture, it is advisable to use more old materials .