IntroductionLightweight Ultra High Performance Concrete (LUHPC) exhibits attributes such as reduced weight, high strength, and minimal shrinkage. As a substrate for paving layers, the surface roughness of LUHPC is a critical determinant of interlayer shear resistance, tensile pullout resistance, and the prevention of early slippage and delamination. Notably, the lower surface hardness of gangue porous aggregates contributes significantly to the textural enhancement of LUHPC surfaces. The incorporation of steel fibers not only strengthens the internal bonding within the concrete but also influences the surface texture of LUHPC after roughening treatments. Despite existing research on the textural properties of pavement surfaces, there remains a gap in understanding the preparation of roughened interfaces for efficient application and the quantitative characterization of macro-micro texture characteristics and roughness influenced by steel fibers, which correlates with interlayer shear performance. While existing research has investigated the texture characteristics of pavement surfaces, there remains a critical need for further exploration into the development of roughened interfaces that facilitate effective implementation, a more detailed quantitative characterization of macro-micro texture and roughness, particularly under the influence of steel fibers, is necessary. Such investigations are crucial for establishing a robust correlation with the interlayer shear performance of heterogeneous paving materials. Additionally, Lightweight UHPC-high viscosity high elasticity binder-SMA specimens were fabricated to assess shear strength across different shot blasting intensities and temperatures. Linear regression analyses were conducted to model the relationships between macro-micro texture parameters and shear strength.MethodsThe surface roughness of gangue aggregate LUHPC was achieved through a shot blasting process, with three-dimensional texture data acquired via a handheld laser scanner. The point cloud data was processed using Gaussian filtering in MATLAB software to reconstruct the specimen's surface topography. Subsequently, both macroscopic and microscopic texture profiles of LUHPC were extracted utilizing a band-pass filter. The influence of steel fibers on the surface roughness of the specimen was assessed. An enhanced evaluation index, the Extended Tectonic Depth (ETD), was proposed, drawing upon the sand laying method's measurement principles. The correlations between macro-texture parameters (R_a, R_q, EMTD, EMPD) and micro-texture parameters (C_MT, RMS) with ETD were analyzed. Furthermore, the relationship between shear strengths of the LUHPC-stress absorbing layer-SMA composite specimen and both macro- and micro-texture parameters was examined.Results and discussionAs the degree of shot blasting increased, the surface of LUHPC became rougher, the ETD grew larger, and the shear performance of LUHPC-high viscosity high elasticity binder-SMA improved at different temperatures. Under the influence of steel fiber, increasing the degree of shot blasting effectively enhanced the overall shear strength. With more shot blasting, the coverage of steel shot on the specimen's surface gradually increased, the depth of sanding continued to grow, the height of the steel fiber protrusions increased, and the peak of the specimen profile became larger, while the surface depth of the non-steel fiber portion tended to be homogeneous. The correlation of the ETD with R_a, R_q, EMPD, and RMS was better, and the correlation with EMTD and C_MT was average. The damage in LUHPC-SMA composite specimens primarily occurred in different surface layers of the bond layer, with no damage to the mixture. he correlation of the shear strength at 25 ℃ with R_q and RMS was good, with an R² greater than 0.85. The multivariate analysis of shear strength and macro-micro texture parameters showed that for bivariate macro texture parameters ETD, EMPD, EMTD, R_a, R_q, the R² was greater than 0.85 at 25 ℃, and ranged from 0.6 to 0.85 at -10 ℃. When the bivariate consisted of micro texture parameters RMS and C_MT, the correlation for both 25 ℃ and -10 ℃ was better, with an R² greater than 0.85. The correlation between shear strength and macro-micro texture parameters improved as the number of variables increased.ConclusionsIn view of the influence of steel fibres on the surface texture of the specimens after shot blasting, EMTD and EMPD were used to replace MTD and MPD to characterize the macroscopic texture properties of the materials more effectively; Based on the measurement principle of the sand laying method, the extended tectonic depth (ETD) was proposed as a new evaluation index. Multivariate linear regression analyses of ETD with macro texture parameters (R_a, R_q, EMTD, EMPD) and micro texture parameters (C_MT, RMS) were carried out, and the results showed that the correlation between ETD and macro-micro texture parameters was strong. According to the comprehensive consideration of each index parameter under different degrees of shot blasting, it was stipulated that the ETD of the extended construction depth of the lightweight UHPC surface in the interval of 0.60-0.70 mm was considered as a light shot blasting effect, the interval of 0.70-0.85 mm was considered as a moderate shot blasting effect, and the interval of 0.85-1.15 mm was considered as a heavy shot blasting effect. The correlation analysis of the shear strength of the composite specimens at -10℃ and 25 ℃ with the macroscopic texture parameters (ETD, EMPD, EMTD, R_a, R_q) and the microscopic texture parameters (C_MT and RMS) showed that: The larger the depth of the extended structure, the better the shear performance at the same temperature; The correlation with the shear strength was gradually strengthened with the increase of the number of variables; and the correlation of the all-variable indexes and shear strength was the best at 0.999. The correlation between all variables and shear strength reached 0.999. Comparing the experimental results under different levels of shot blasting, it was concluded that the extended structural depth of lightweight UHPC surfaces had a positive correlation with the shear strength, and therefore the extended structural depth of ETD was recommended to be 0.85-1.15 mm in this paper.