چكيده به لاتين
In concrete 3D printing technology, the cementitious material is deposited layerwise with a specific printer used to form the final concrete model or structure. In spite of few studies on mix designs and material selection for utilizing in this technique, however, there is not a relatively comprehensive investigation of the effects of additive and the intrinsic properties of cement materials on the behavioral properties of 3D printed concrete. In this thesis, we intend to introduce appropriate mix designs for this process by applying different construction materials for this process and investigate the properties of 3D printing technology. To do so, first, a 3D printer was fabricated in laboratory scale. Then, by studying the available resources, the effect of materials on mechanical properties, stability and mechanical resistance properties of different concrete were determined and then different mixes were defined for the use of mortar in the 3D printer. Flowability, open time, stability, and compressive strength of printed samples were among the investigated parameters. These tests were carried out on the water to binder ratio, the amount of aggregate, superplasticizer agent and pozzolanic additives such as Microsilica, Glass blast furnace slag and calcium aluminates cement. According to the results of the experiments, Microsilica powder was obtained as the most suitable pozzolanic additive of portland cement in the printed mortar (with 10% replacement with PC). For GBFS, 10% replacement ratio was also achieved wich provided appropriate features for 3D printable concrete. It was determined that the incorporation of CA cement should be limited to 5% of total binder to give applicable open time. Also, it has been observed that the use of 0.8 to 1 percent polycarboxilate based superplasticizer of the total weight of binder give the most optimal properties in terms of rheology, stability and mechanical strength to the printed mortar. Furthermore, the results show that the fine aggregate to binder value of 1.4 and the water to binder ratio of 0.3 is the most optimal values in all of the examined mix designs.
