Bond Performance And Interface Simulation Of Supersulfate Cement Based Pavement Repair Materials

With the rapid growth of road traffic flow in China,many roads experience damage due to heavy traffic loading,which appeared with fissure,protuberance,breakage,fracture,and so on.If not repaired in time,these damages will continue to expand to form more serious diseases,bringing greater safety problems and economic losses.Supersulphate cement is a kind of clinker less or no clinker cement with granulated blast furnace slag as the main raw material,gypsum as sulfate exciter,and clinker or lime as alkaline exciter,which has the advantages of simple preparation process,economic and environmental protection,low exothermic heat of hydration and strong resistance to sulfate erosion,etc.It is suitable for use as a road repair material.In this paper,high alkali red mud was used to replace part of the blast furnace slag as both raw material and excitation agent,and water glass was used as an excitation agent.The effects of red mud content,water glass modulus,and content on the performance of supersulphate cement were studied,and the optimum ratio was determined.The bonding interface between the repair material and the old substrate was simulated by ANSYS software.The following conclusions were obtained from the above studies.(1)The results show that with the increase of the modulus and content of water glass,the compressive strength of the sample increases.when red mud was mixed alone,the strength of the specimens was highest at 10 wt.% of red mud.Through the Taguchi method,the best mix ratio is 70 wt.% slag,15 wt.% gypsum,5 wt.% OPC,10 wt.% red mud,2.0 wt.% 1.8M water glass.From the microscopic analysis,it is known that the main hydration products of the cement are ettringite and C-S-H gel.With the increase of the p H value of the cement system increased,the morphology of the C-S-H gels changed.The C-S-H gel changed from fibrous to sheet-like structure,showing a “fish scale” morphology and “foil-like” morphology.(2)The results show that as the roughness of the bonding surface of the old matrix increases,the bonding strength between the new and the old materials increases.Too dry and too wet the bonding surface will cause the w/b ratio at the bonding interface to be different from other parts,affecting the morphology of hydration products at the bonding interface,and affect the bonding strength.With the use of an interface agent,the interface agent fills in the pores created by the manufacture of roughness,improving the mechanical bite between the old and new material and therefore increasing the interface bond.Based on the backscattered electron(BSE)results,the bonding interface occurs the so-called “wall effect”.This caused the interface connection is not tight and the porosity to increase.On a macro level,this is reflected in a reduction in bond strength.(3)Based on the ANSYS finite element analysis software and the bond performance,the simulation analysis of old and new materials is carried out.The results show that for the entire bonded sample when a load is applied,the stress at the bonding interface is significantly greater than other parts of the sample.As the roughness increases,the stress at the interface increases.The results show that for the bonding interface when a load is applied,the rough surface is conducive to the dispersion of stress.Therefore,the rough surface can withstand greater loads.The Force-Displacement Curve simulated by the finite element model is linear,with the maximum load that the specimen can withstand increasing with increasing roughness,and consistent with the actual results.