Research On Surfactant-Assisted Warm-Mix SBS Asphalt Foam Technology

In the context of global "carbon peaking" and "carbon neutral",the concept of green and sustainable development has been deeply implemented.Warm mix asphalt technology is economical and environmentally friendly,but pure foam asphalt has limited temperature reduction and has problems such as high moisture sensitivity,poor foaming performance and poor coating of aggregates by the foam.Surfactants can improve the foaming effect of asphalt and make it easier for asphalt to spread on the surface of the aggregate,thus enhancing the aggregate-foam asphalt adhesion and improving the water stability of asphalt mixes.Based on the above analysis,the main research contents and conclusions of this paper are as follows:(1)Based on the foaming characteristics of asphalt,the effects of foaming water quantity,asphalt temperature and surfactant on the foaming effect of 70# matrix asphalt and SBS modified asphalt were investigated,and the mechanism of surfactant’s effect on asphalt foaming was analysed.The most significant effect on the foaming effect of asphalt was found to be the amount of water used for foaming,followed by the temperature of asphalt;the optimum foaming conditions for SBS modified asphalt were determined to be 1.5% water used for foaming and 170°C foaming temperature;the half-life of SBS asphalt foaming could reach more than 22 s when cetyl trimethyl ammonium chloride and sodium methyl cocoyl taurate were mixed at 1.0%,which significantly improved the stability of the foamed asphalt.(2)SBS modified bitumen was selected as the base binder and the effect of surfactants on the conventional performance of SBS asphalt foam was investigated.The results showed that the residual air bubbles inside the SBS asphalt gradually dissipated with time,and its conventional properties were similar to those of the original SBS asphalt;cetyl trimethyl ammonium chloride and sodium methyl cocoyl taurate could enhance the high temperature and aging properties of the SBS asphalt to a certain extent,but had no significant effect on other properties.(3)The effect of surfactants on the high-temperature rheological properties and fatigue properties of the foamed SBS asphalt was investigated by the temperature scan and time scan modes of the dynamic shear rheometer,and the effect of surfactants on the aggregate-foam asphalt adhesion properties was analyzed from the surface free energy theory.It was found that the high temperature rheological properties and fatigue properties of SBS modified bitumen decreased after foaming,and the three surfactants enhanced the high temperature properties of SBS bitumen,but its fatigue properties decreased a little;the water adhesion function of aggregate-asphalt decreased after foaming of SBS modified bitumen,and the surface properties of SBS bitumen were changed by cetyl trimethyl ammonium chloride and sodium methyl cocoyl taurate,and the surface properties of SBS bitumen were changed by cetyl trimethyl ammonium chloride and sodium methyl cocoyl taurate.When cetyl trimethyl ammonium chloride was mixed with 1%,the water and anhydrous adhesion function of aggregate-foam SBS asphalt increased by 11% and 8% respectively,which had a positive effect on the adhesion of foam asphalt-aggregate.(4)The surfactant-assisted warm-mix SBS asphalt mixes were proportionally designed,and the compaction characteristics of the warm-mix SBS asphalt mixes were studied based on the volumetric index method,and the warm-mix effects of the three surfactants and their effects on the road performance of the mixes were analysed.The results showed that the temperature of the surfactant-assisted warm mix SBS asphalt mixture was at most 10℃ lower than that of the conventional foam SBS asphalt mixture;cetyl trimethyl ammonium chloride and sodium methyl cocoyl taurate significantly enhanced the high temperature rutting resistance of the foam SBS asphalt mixture.Above,the resistance to water damage was significantly improved,while the low temperature performance was basically unaffected,but still met the specification requirements.