3D printing technology which also known as ‘additive manufacturing’, contains a fabricating process producing a 3 dimensional object with a breeds of raw materials based on the virtual design under computer conductions. Basically, 3D printing process can be divided into two categories: direct deposit and selective reaction. The direct deposit is a process of squirting, spraying or squeezing liquid, paste, or powdered raw materials through printing nozzle while the selective reaction is a process of using heat, light or binder to solidify a light sensitive photopolymer or powder based materials.

The main purpose of this thesis is to examine the feasibility of cementitious composites as the selective reaction 3D printing materials, including the printability of the raw materials, mechan...[ Read more ]

3D printing technology which also known as ‘additive manufacturing’, contains a fabricating process producing a 3 dimensional object with a breeds of raw materials based on the virtual design under computer conductions. Basically, 3D printing process can be divided into two categories: direct deposit and selective reaction. The direct deposit is a process of squirting, spraying or squeezing liquid, paste, or powdered raw materials through printing nozzle while the selective reaction is a process of using heat, light or binder to solidify a light sensitive photopolymer or powder based materials.

The main purpose of this thesis is to examine the feasibility of cementitious composites as the selective reaction 3D printing materials, including the printability of the raw materials, mechanic properties and microstructural characterization of printed product.

Feasibility of cementitious composites as an applicable materials in selective reaction 3D printing technology can be characterized through its printability during printing process, mechanical properties of printed products and the reaction degree observed in microstructures. In this study, experimental work of different mixing proportions of cementitious composites were carried out to examining the feasibility. Firstly, the printing strategy of selective reaction 3D printer was analyzed through typical experimental study of deposition method, compaction mechanism, nozzle selection and liquid rheology, etc. The printing and post process were also investigate during the study. Secondly, Magnesium Potassium Phosphate Cement (MKPC) as a fast repairing material is a good type of material which can be fabricated through selective reaction 3D printer. It can be found that, adding the certain amount of light burned Magnesia oxide (MgO) into MKPC system will surly enhance the mechanical property of printed product. The particle size distribution is the key factor influencing the condition of layer making, which can affect the bonding strength of final printed products. In the modification of selective reaction 3D printer, the nozzle size of 0.06mm and 0.12mm (inner diameter) was suitable to be adjusted with cementitious materials especially for MKPC and alkali-activated cementing components. Feasibility of alkali-activated cements were also investigated through fabricating alkali-activated slag and alkali-activated fly ash. Due to the hydration properties of alkali-activated cements, post processing of curing in high temperature was suggested to be applied to the fabricated products. At last, the combination material system of MKPC and alkali-activated cementing components were also utilized in selective reaction 3D printing system to analysis the mechanical behavior and hydration properties of fabricated composite products. It can be concluded that, the mechanical properties is basically influenced by the setting time of each printing trips of materials, roughness of surface in each printing layer, interaction between overlap distance in each strip and degree of uniform distribution of mixing raw materials.

The main contributions of this study includes investigated the feasibility of cementitious composites utilized in selective reaction 3D printers through modifying a suitable 3D printer which satisfied with printability of cementitious materials and then optimized mixing proportions for magnesium phosphate based materials as well as alkali-activated materials. The selective reaction 3D printer is fully satisfied with cementitious materials in civil engineering not only because its availability for powder formed materials, but also its capability of adjustment in different printing mechanism. It is very flexible in improving jetting system to fit different reaction mechanism of materials system.