Microscopic Study And Performance Analysis Of Strength Formation Structure Of Foamed Bituminous Recycled Mixture

The foamed asphalt cold regeneration technology has the advantages of simple construction,low cost,energy saving and environmental protection.Thus it should have a wide application space in Heilongjiang Province.However,there is no relevant engineering application with this technology in this region.Moreover,the majority of relevant studies focus on the macroscopic performance of foamed asphalt.There are a few microscopic studies which investigate the strength-forming structure of foamed bituminous reclaimed mixes.Therefore,further research is needed.As the cold recycling technology of foamed asphalt is greatly affected by materials and local environment,systematic lab-based experiments should be conducted before practical applications in this province.In view of this,according to the characteristics of materials and the specific environment conditions of Heilongjiang province,this article carried out several indoor experiments.The aim of the present study was to explore the effect of different factors,i.e.,the amount of asphalt,mixing water consumption and cement content,on the macroscopic properties and microstructure of the reclaimed mixture products.This study successfully found the influential mechanism of target contributors,and the research contents and achievements are as follows:Firstly,this study conducted an indoor foaming experiment with the commonly used asphalt in Heilongjiang province.Based on the forming mechanism,the present study analyzed the correlations and influential significances between forming results and other different factors: the asphalt type,temperature and water consumption.The best asphalt forming conditions asphalt was obtained in this studySecondly,according to the gradation characteristics of old materials,different mix ratios were designed.The best water consumption was obtained through compaction test,and the best amount of asphalt was obtained by using splitting strength as the control index.The test results of the performance of the mixture,using the freeze-thaw splitting test,show that a reasonable amount of asphalt can ensure good water stability,and the graded road performance can meet the requirements.Thirdly,the influence of asphalt content,mixing water content and cement content on the strength and stiffness characteristics of foamed asphalt cold reclaimed mixture was investigated through laboratory experiments.The performance of reclaimed mixture was studied under freeze-thaw cycles.This study found that with reasonable amount of asphalt and mixing water,we can get the mixture with excellent mechanical properties.Also,the increase of cement content can increase the strength and water stability of the mixture.Moreover,with the number of freeze-thaw cycles increases,the strength of the mix decreases and the void fraction increases.Finally,this study qualitatively described the microstructure of foamed asphalt cold reclaimed mixture.The image processing technology was used to obtain the information of fractured specimens,and then an index was established to quantitatively evaluate the dispersive properties and distribution uniformity of asphalt.Then,the effect of the amount of asphalt,mixing water,cement content and moisture intrusion this index were being analyzed.Concerning the macroscopically mechanical properties,the influence of different factors on the forming asphalt performance are obtained as follows: The amount of asphalt and the amount of mixing water will affect the asphalt dispersion properties and distribution uniformity.The increase of cement content has little effect on asphalt dispersion properties,so it can increase the strength of free packing part.After water intrusion,the strength of free packing part decreases rapidly,which results in a rapid decline of mechanical properties.