Study On Performance Of Cold Recycling Mixture With Emulsified (Foamed) Asphalt

The asphalt pavement constructed in the 1980s in our country early is entering into rehabilitation period, which produces a large amount of reclaimed asphalt mixture.The technology of asphalt pavement rehabilitation, which can reuse the old asphalt mixture, raise resource utilization ratio and protect ecological environment, accords with the strategic policy of developing recycle economy and realizing sustainable development in our country. So the study of the cold recycling technology has important practical significance.The study of cold recycling mixture mainly focuses on the material mixture design and conventional strength currently . However, studies about the permanent deformation performance,the resistance to shear performance and dynamic modulus about cold recycling asphalt mixture have a little at present. Through a lot of laboratory experiments, the paper aims to systematically study permanent deformation performance, fatigue performance, resistance to shear performance and dynamic modulus of the cold asphalt recycling mixture with emulsified,and also compared with foamed asphalt mixture.The permanent deformation of emulsified asphalt recycled pavements is very important for pavement structure. The paper adopted the dynamic compression creep test to analyze the effect of mix composition on permanent deformation . It was found that increasing a amount of cement or decreasing emulsified asphalt content at a certain degree, it can improve the deformation resistance of the cold recycling mixture with emulsified asphalt. Foamed asphalt recycled mixture has superior deformation resistance over emulsified asphalt recycled mixture.Fatigue resistance is a paramount performance needed to be optimized for cold recycling mixture with emulsified asphalt, which are used for base or subbase layers in pavements. This paper adopts the indirect tensile fatigue test to study of the influence of different material compositions on fatigue properties of emulsified asphalt recycled mixes. The results showed that with increasy of cement at a small amount, the improvement of fatigue resistance for emulsified asphalt recycled mixtures. The recycled asphalt mixes at optimum emulsified asphalt content have relatively good fatigue resistance, strength and flexibility. The stress sensitivity of foamed asphalt recycled mixture is higher than the emulsified asphalt recycled mixture. Fatigue resistance of emulsified asphalt recycled mixes is between semi-rigid material and HMA. The paper uses the penetration shear test to study of the influence of different material compositions on shear resistance performance of emulsified asphalt and foamed asphalt recycled mixes at the temperature of 25℃and 60℃. It was indicated that increase of cement is beneficial to the increase of shear index for emulsified asphalt and foamed asphalt recycled mixes. With the increasing of emulsified asphalt and foamed asphalt content,the maximum shear stress and internal friction angle are decreased, but the cohesion is increased at first then decreased. The maximum shear stress of foamed asphalt recycled mixes is larger than emulsified asphalt recycled mixes.The Hamburg rutting test is used to analysis water stability of cold recycled mix with different asphalt properties. The water stability of asphalt mixture is ranked as follows:shell SBS modified emulsified asphalt>foamed asphalt> shell general emulsified asphalt> domestic emulsified asphalt Y.The study on dynamic modulus of cold recycling mixture can provide the basis for cold recycling layer design and mixture performance evaluation. The paper uses dynamic triaxial tests to study the dynamic modulus of different material compositions,temperature and confining pressure of emulsified asphalt and foamed asphalt recycled mixes.The results shows that the dynamic modulus increases with the increase of confining pressure, cement amount and the decrease of emulsified (foamed)asphalt amount and temperature.