Preparation of preplaced aggregate concrete and experimental study on its strength

•Formulation and formation methods for PAC under certain conditions are proposed.•Strength grade of the non-vibration-formed PAC can reach C30 with a w/c of 0.42.•Strength grade of the vibration-formed PAC can reach C40 with a w/c of 0.42.•PAC has a higher tension-compression ratio than that of normal concrete at the same w/c.•Compressive failure essence in the PAC is consistent with that in normal concrete. In this study, preplaced aggregate concrete (PAC), a type of coarse aggregate interlocking concrete, was prepared. The preparation process comprises the following two main steps: first, the coarse aggregate was piled in a certain way to form a natural skeleton; then, the skeleton was filled with the formulated mortar. In this case, the skeleton was fully filled with the mortar and cemented into an integral body due to the hydration of cement; thus, a type of coarse aggregate interlocking concrete was obtained. To determine the relationship between the strength grade (C20, C30, and C40) and the water-cement ratio (w/c) of the PAC, and to explore the essence of the compression failure in the PAC at the mesoscopic level, tests were conducted to investigate the compressive strength and splitting tensile strength of the PAC. The test results reveal that when the non-vibration-forming method was employed, the strength grade of the PAC reached C20 when the w/c was 0.54 or 0.48, and reached C30 when the w/c was 0.42; when the vibration-forming method was employed, its strength grade reached C20, C30, and C40 when the w/c was 0.54, 0.48, and 0.42, respectively; for the same w/c, the tension-compression ratio of the PAC was higher than that of the reference concrete (C). Thus, the preplacing of the coarse aggregate benefits the tensile strength development of concrete. Moreover, from the mesoscopic aspect, the compression failure tests on the concrete demonstrate that the essence of the compression failure in the PAC is similar to that in the C. The conclusions obtained from this study can be used as a reference for the preparation, formation, and deeper research of PAC.