Structural rebuilding of concrete materials in 3D printing with various types of additives

Abstract

Traditional constructing method can be time-consuming. Limits also exist in traditional construction method. Concrete 3D printing is a kind of novel in-situ construction method which eliminate the use of form works. With the help of robots, construction can be flexible in 3D space. Manpower and time can be effectively saved. As precondition of successfully applying the concrete 3D printing, some rheology property (yield stress, viscosity, thixotropy) of the concrete paste must be satisfied because there is no formwork. Inter layer bonding property is one of the weakness of 3D printed concrete structures. This paper investigates different additives (retarder, reducer, superplasticizer and accelerator) which may help obtain required properties for successful 3D printing. The hydration, thixotropy and side effect are also considered and the hydration process and rheology changing in the time domain are combined to analyze the structural building process. A molecular absorb model is used to explain the micro-scale mechanism. At last, mechanical property of the printed filaments is used to estimate the result.