| Concrete pavements in tunnels are susceptible to gradual deterioration of skid resistance due to abrasion during service,which poses a great risk to traffic safety.Polymer-modified cement mortar(PCM)can be used to repair the skid resistance of old concrete pavements,however,there is still a lack of research on how polymer emulsions can improve the skid resistance and skid-resistance durability of cement mortars.Therefore,this paper reveals the improvement of the skid resistance and skid-resistance durability of PCM from the perspective of surface texture morphology based on the Close-up photography technique.In this paper,ethylene-vinyl acetate copolymer emulsion(EVA),carboxyl styrene butadiene latex(XSBRL)and styrene butadiene latex(SBR)were selected to prepare polymer cement mortar(PCM),quick-setting agent and thixotropic lubricant on the physical and mechanical properties of PCM were analyzed to optimize the material composition of PCM,and the effects of polymer emulsions on the rheological properties and internal microstructure of cement paste were investigated;the surface texture information of PCM was extracted by Close-up photography technique and the 3D surface texture model was established to investigate the effects of three polymer emulsions on the texture roughness and skid resistance of cement mortar,and to clarify the connection between texture roughness and skid resistance;finally,a three-round abrasion tester was used to simulate the abrasion behavior of pavement under traffic load,and the decay of the skid reisistance and the surface texture of PCM was investigated,and then the decay model of the skid reisistance based on the surface texture was established.The results showed that the polymer emulsions improved the fluidity and water retention of the fresh mortar as well as the denseness and cohesion of the hardened mortar,increased the number and uniformity of surface sand particles,and resulted in a general improvement in the surface texture roughness of the three PCMs.All three polymer emulsions enhanced the thixotropy of the cement paste,and EVA and XSBRL also enhanced the yield stress and apparent viscosity of the cement paste,but not SBR;meanwhile,EVA and SBR caused the cement paste to exhibit a "honey"-like rheological behavior,while XSBRL caused the cement paste to exhibit a "toothpaste"-like rheological behavior.The complex variation in rheological properties caused differences in the improvement of the texture roughness by the three polymer emulsions,which in turn caused differences in the skid resistance of the three PCMs:The improvement of surface texture height(Sa),symmetry(Ssk),and core material volume(Vmc)by EVA significantly enhanced the skid resistance of cement mortar,while the improvement of texture sharpness(Sku),slope(Sdq),peak material volume(Vmp),and surface area(Sdr)by XSBRL,although lower than EVA,was significantly higher than that of SBR.The texture abrasion resistance of the three PCMs was improved by the wrapping and filling effect of polymer films and particles on cement hydration products.EVA and XSBRL containing reactive groups formed a 3D cross-linked network structure inside the cement paste and the number of cross-linked network structures inside E-PCM was higher than that of X-PCM,making E-PCM the best and S-PCM the worst in terms of textural abrasion resistance.The anti-slip durability of both E-PCM and X-PCM was better than that of S-PCM,but the size relationship between the E-PCM and X-PCM was related to the polymer content.The attenuation of the anti-slip performance of PCM had a high causal relationship with the variation of the surface texture parameters Sa,Sku,Vm and Spd,indicating that the attenuation of the anti-slip performance of PCM was caused by the abrasion of the surface texture. |
