Preparation And Performance Of Warm Mix Asphalt Additives Based On Geopolymer

Warm-mixed asphalt mixture technology is a new technology that can achieve asphalt mixture mixing at a lower temperature.It plays an active role in saving energy,reducing energy consumption,and improving the durability of asphalt pavement,which has become the focus of world attention of scholars.Geopolymers are used as warm mixing aids for asphalt mixtures.Free water in geopolymers is heated and foamed in the asphalt,causing the volume of the asphalt to expand,thereby reducing the viscosity of the asphalt and making the asphalt have a active effect on fluidity at lower temperatures.In this paper,a geopolymer warming agent was prepared with sodium hydroxide and water glass as stimulants,and its basic physical properties and water loss characteristics were studied by using infrared spectroscopy,X-ray diffraction,thermogravimetry,and scanning electron microscopy.At the same time,the physical properties,chemical composition of geopolymer-asphalt,and the foaming regularity and bubble size of geopolymer in asphalt were analyzed;In addition,the road performance of the geopolymer asphalt mixture was evaluated by the compactness effect of the geopolymer asphalt mixture comprehensively.The main research results and conclusions are as follows:(1)The best preparation condition of geopolymer warming agent is that the silicon-aluminum ratio is 3:1,the stirring time is 8min,the curing time is 72h,and the modulus is 1.4;Geopolymer warming agent is mainly amorphous,with many pores,forming a parallel plate slit-like mesoporous structure with an average pore size of 11.09nm and a specific surface area of 47.658m~2/g;The adsorption process of geopolymers can be divided into three stages:single-layer adsorption,multi-layer adsorption,and capillary condensation.The desorption process is opposite to the adsorption process.Under normal temperature conditions,geopolymer warming agents have good water retention and stability.(2)Geopolymer warming agent has limited impact on the physical properties and chemical composition of asphalt.According to the asphalt viscosity-temperature curve,the optimal blending amount of geopolymer warming agent is 6%,and the optimal mixing temperature is 140°C.The water release process of geopolymer warming agent in asphalt can be divided into two phases:(1)vaporization phase;(2)foaming phase.The size and distribution of air bubbles in the asphalt are affected by the stirring time.Compared with ordinary asphalt mixtures,geopolymer asphalt mixtures have considerable volume performance and better high-temperature stability,but water stability will decrease.(3)During the asphalt heating process,dehydrated and non-dehydrated geopolymers with an amount of 6%(asphalt quality)can effectively inhibit the discharge of asphalt volatiles and respirable particulate matter,and delay the time to reach the limit of serious pollution;In addition,the inhibitory effect of 0.3%geopolymer on particulate matter is not obvious,and the 3%polymer can significantly reduce the emission of particulate matter.