Rheo-Mechanics Modeling for Constructability Quantification of 3D Printed Concrete скачать в хорошем качестве

Rheo-Mechanics Modeling for Constructability Quantification of 3D Printed Concrete

Presented By: Jacques Kruger, Stellenbosch University Description: 3D printing of concrete (3DPC) generally necessitates that a material readily flows when pumped without any form of segregation present, while also attaining plastic state strength at a high rate for adequate buildability performance once extruded. This complex material behavior consisting of varying time and shear-dependent viscosity is best captured via rotational rheometry. In this work, a bi-linear analytical thixotropy model is initially derived that specifically pertains to 3D printing of cementitious materials. Thereafter, mechanics (i.e. failure criteria) are coupled to the bi-linear material model to yield individual rheo-mechanical predictive models for the quantification of 3DPC constructability, here defined as the holistic fresh state construction process comprising of pumping and extrusion, filament shape retention and buildability. A brief overview on the derivation for each analytical model is presented and experimental verification cases proffered. Thereafter, it is shown how these models can be integrated and utilized to optimize print parameters, essentially yielding the print speed and filament layer height combination that will result in the successful construction of a specified object in the least amount of time. This in turn ensures that the smallest possible pass time is obtained, or time between deposition of successive filament layers, to ultimately achieve the highest degree of mechanical and durability performance for 3DPC elements.