Foam Asphalt Macro And Micro Evaluation And Mixture Performance Studiese

Foamed asphalt warm mix technology can reduce the harmful gases emitted by traditional hot mix asphalt mixtures,while reducing the construction temperature,and the environmental benefits are obvious.At the same time,compared with other warm mix technologies,there is no need to use chemical additives,and the economic benefits are obvious.However,the effect of residual moisture of foamed bitumen on asphalt binders and mixtures is not clear.This paper aims to comprehensively analyze and evaluate the characteristics of foamed bitumen from macro and micro perspectives,study the influence of bubble micro presence and residual moisture on macro properties,compare high-efficiency foamed asphalt materials,and demonstrate and apply the research results.（1）Experimental study on the foaming characteristics of foamed asphalt:explore the influence of asphalt type,foaming agent,foaming temperature,water consumption and other factors on the foaming effect of foamed asphalt,and determine the optimal foaming conditions.The results showed that water consumption had the greatest influence on the foaming effect.Maoming 70^#matrix asphalt foaming effect is the best,the best foaming conditions are foaming temperature 150°C,water consumption 1.2%;The best foaming condition of Zhenhai 70^#matrix bitumen is 150°C foaming temperature,and water consumption of 0.9%is used as the best foaming condition;The best foaming conditions of Zhonghai 70^#matrix bitumen are foaming temperature 150°C and water consumption of 1.6%.The half-life of the blowing agent on bitumen was obvious,among which cetyltrimethylammonium bromide had the greatest effect on bitumen foaming,and the expansion rate of matrix bitumen increased by 21.5%and the half-life by 63.64%.（2）The conventional properties and rheological properties of foamed bitumen were explored:the viscosity of bitumen in the foaming process decreased significantly,and the viscosity gradually decreased as the foaming temperature increased;Dynamic viscosity is inversely proportional to the expansion rate.The rheological properties of bitumen were studied by dynamic shear rheometer（DSR）and low-temperature bending beam rheometer（BBR）.The residual moisture after foaming has a certain degree of reduction in the high temperature performance and fatigue performance of asphalt;The high temperature performance of cetyltrimethylammonium bromide was restored by the foaming agent;The foaming agent sodium dodecyl benzenesulfonate has the best effect on the fatigue performance recovery of matrix asphalt;The low temperature performance of the foamed bitumen was not significantly improved by the blowing agent.（3）The microscopic properties of foamed bitumen were explored:infrared spectroscopy was used to find that no new functional groups were generated in the foaming process,and the absorption peak intensity at 1019cm^-1 wavenumber was significantly improved by the use of cetyltrimethylammonium bromide,which improved the fluidity of foamed bitumen.The bubbles were effectively retained by freezing method,and the fluorescence microscope polarization mode was used to observe the presence of dense areas and evacuation areas of the bubbles,and the fluorescence mode found that cetyltrimethylammonium bromide combined best with bitumen,which was consistent with the law of the best macroscopic foaming effect.Based on the surface free energy theory,the adhesion of foamed bitumen was evaluated,the surface energy of bitumen was calculated by lying drop method,and compared with the adhesion work before and after foaming of foamed bitumen,it was found that the surface energy of matrix bitumen and SBS modified bitumen decreased after foaming,and the adhesion of SBS modified bitumen after foaming was significantly less affected by residual moisture.After foaming with the addition of three foaming agents,the surface energy and adhesion work of the bitumen exceeded that before foaming.（4）Design the mixing ratio of foamed asphalt warm mixture:determine the best oil-stone ratio is 4.9%,the best compaction temperature is 125°C,and the mixing temperature is 135°C.Compared with the high temperature stability,low temperature crack resistance and water stability of hot mix asphalt and foamed asphalt warm mix mixture,its road performance and hot mix asphalt mixture decreased slightly,which met the specification requirements.According to the indoor test results,the physical engineering application was carried out,the paving and rolling temperature during construction was reduced by25°C,and the harmful gases such as asphalt smoke were greatly reduced,and the on-site test results showed that the road performance of the foamed asphalt warm mix mixture used in this paper was good.