Research On Preparation Of Foamed Asphalt And Erformance Of Foamed Asphalt Cold Recycling Mixture

In21st century, the highway construction technology is maturing. China’s highway construction has entered a period of rapid growth. In the rapid growth of road construction, road maintenance issues have become increasingly prominent.Road maintenance will generate a lot reclaimed asphalt pavement. Discarding the reclaimed asphalt pavement materials can cause environmental pollution and waste asphalt material resources. It does not only comply with the principle of sustainable development of China. Foamed asphalt cold recycling technology not only to the effective use of reclaimed asphalt pavement recycling material, and also saves resources, energy and time, then meets the modern society, sustainable development of low carbon environmental requirements.This article depends on the national key topic—863topic 《Central technologies and equipment of full thickness Asphalt Pavement Cold Recycling》(2009AA11Z106), and have research on performance of foamed asphalt and foamed asphalt cold recycling performance of the mixture. This article main research content includes the following aspects:Asphalt foaming principle and burst mechanism of foamed asphalt; Research and development of laboratory asphalt foam equipment and its operating parameters to determine; Experimental analysis of self-development of asphalt foaming equipment for the asphalt foam impact factors; Reference to the cold recycled mixture of foamed asphalt at domestic and international with the design method, a complete and easy operation of foamed asphalt cold recycling mixture design method is established; Based on the factor of type and amount of foamed asphalt, mineral aggregate temperature, mixing water consumption, curing conditions and cement mixing amount, performance of foamed asphalt cold recycling mixture was analyzed。After more than a year of design and development of foamed asphalt testing machine, it’s not only lower the cost of equipment cost, and reliable, and easy to operate, which produces foamed asphalt fully meet fully meet the foaming effect of 《Technical Specifications for Highway Asphalt Pavement Recycling》(JTG F41-2008) requirements (foamed asphalt half-life greater than8s, the expansion ratio of greater than10times). Using this asphalt foam testing machine do foaming experiments with three kinds of asphalts. Huateng AH-70asphalt at150℃and the foaming water consumption of2%foaming effect reach the best, which half-life is10s and maximum expansion is13times. Donghai AH-70asphalt at160℃and the foaming water consumption of3%foaming effect reach the best, which half-life is10.1s and maximum expansion is12times. Huateng AH-90asphalt at150℃and the foaming water consumption of2%foaming effect reach the best, which half-life is10.6s and maximum expansion is11.5times.Impact factors analysis of asphalt foaming test results shows that:The same asphalt in the same foaming temperature, half-life with increasing water consumption become larger, while the expansion ratio with increasing water consumption become smaller; Above asphalt can be foamed temperature, foaming temperature have no necessary connection with foaming effect; Different types of asphalt have different components, so foaming effect there is a big difference; Different grades asphalts have different viscosity, so compared to low viscosity asphalt have longer half-life, but its expansion is relatively small; Increasing the foaming water temperature can conducive to produce droplets gasification in the foamed asphalt produce process,so it improve the foaming effect. But the proportion of elevation is small, so general practice use of water at room temperature to produce foamed asphalt.Referencing to the cold recycling mixture ratio design method at home and abroad, we establish a complete and easy operation foamed asphalt cold recycled mixture design method. Using of this design method, the test of foamed asphalt cold recycling mixture ratio to determines follows:75%RAP+23%new aggregates+2%cement. The best Huateng AH-70foamed asphalt content is3%.Its Marshall specimens ITS is0.512MPa and ratio of wet ITS and ITS is81.2%, These test result meet the cold recycling mixture ratio design method requirement that ITS greater than0.4MPa and ratio of wet ITS and ITS greater than75%.The same kind of foamed asphalt cold recycling mixture exist best foamed asphalt content. Huateng AH-70best foamed asphalt content and Donghai AH-70best foamed asphalt content of this kind of cold recycling ratio design mixture are all3%.For best mixing water with a foamed asphalt cold recycled mixture, best mixing water of this mixture is the ratio of optimum moisture content of75%to85%. When foamed asphalt cold recycling mixture applied to the actual, mineral aggregate mineral aggregate temperature should not too low and the general temperature that below10℃is not suitable for foamed asphalt cold recycling. With a kind foamed asphalt cold recycled mixture, cement content is not as high as possible. The best cement content of this foamed asphalt cold recycling mixture is1%to2%.