Sand-clay mixtures are often employed as typical reconstituted soils for geotechnical experiments in the laboratory. Sample preparation is an important factor that influences the mechanical behavior of reconstituted clayey soils. It is necessary to use an adapted sample preparation procedure to ensure an optimized sample homogeneity for sand-clay mixtures. There are various methods of soil sample preparation documented in the literature; however, the effect of sample preparation on soil–structure interface shear behavior and soil physical properties has not been well investigated so far. The objective of this paper is to characterize how sample preparation affects the shear behavior of the sand-clay mixture–structure interface and the related physical properties. Sand-clay mixture specimens with clay fractions of 13.75 %, 27.5 %, 41.25 %, and 55 % are prepared by the slurry method and the dry tamping method for the tests. Direct shear tests were carried out on the sand-clay mixture–concrete interface through a device in the laboratory. The physical parameters of the sand-clay mixture samples were measured after the sample preparation and shear tests. A comparison of these results provides an understanding of the role of sample preparation on the sand-clay mixture–concrete interface shear response and physical properties of the samples.