الفهرس 
Title : Design Of Geopolymer Composites For 3d Printing Applications
SummaryOnly 14 pages are availabe for public view
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Abstract
Lately, several attempts have been made to enhance the environmental friendliness of concrete to make it more appropriate as a ”green building” material and increase the tensile strength of cement composites. However, emissions of greenhouse gases such as CO2 and CO are the primary causes of global warming. One ton of ordinary Portland cement produces about one ton of CO2. The cement industry is one of the large energy-intensive industries, emitting a high amount of carbon dioxide (CO2) due to limestone calcination and fossil fuel combustion. 5% of these emissions are man-made on a global scale, chemical manufacturing processes 50%, and 40% are caused by fuel combustion. Extensive research has been conducted to mitigate the cement industry’s impact, either by increasing the efficiency of the cement manufacturing process or by utilizing byproduct supplementary cementitious materials (SCMs) such as fly ash, ground granulated blast furnace slag GBFS, natural pozzolans, metakaolin, and silica fume, to replace ordinary cement partially. Supplementary cementitious materials have been researched in concrete as pozzolanic materials that react with CH to form extra C-S-H. These compounds have been shown to enhance the mechanical qualities of concrete and its workability and durability.
While several publications promote geopolymers as a ”green” concrete alternative, few studies have measured the environmental effects of geopolymers using the Life Cycle Assessment approach. Concerning metakaolin-based geopolymer concrete, it has been shown that because of the low Si/Al ratio in MK, a considerable quantity of sodium silicate is needed, which negatively influences the environment. Numerous studies have shown that the approach described uses less slag than pure BFS geopolymer concrete. In comparison to pure MK-based geopolymer, this option needs less sodium silicate. A mixture of MK and BFS is used to lessen environmental effects since they include less BFS than a pure BFS geopolymer and also have a considerably lower sodium silicate solution content than a pure MK-based geopolymer. As a result, future research and development in geopolymer concrete technology should concentrate on two viable alternatives. To begin with, the utilization of non-recyclable industrial waste and, secondly, the manufacturing of geopolymer concrete using a mixture of blast furnace slag and activated clay. Additionally, geopolymer concrete production would benefit from the use of waste material with an appropriate Si/Al molar ratio to minimize the quantity of sodium silicate solution utilized.
3D printing technology in the construction sector has garnered considerable interest from scholars and industry practitioners worldwide. This is because 3D concrete printing can enhance concrete construction by lowering construction waste significantly, cost, and time, while also boosting construction safety and geometric flexibility. 3D printing technology enables an unprecedented degree of accuracy and design flexibility. The architects’ vision will no longer be harmed by the human limitations of master builders and bricklayers. Successful creation of printed concretes involves a thorough knowledge of the rheological
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requirements for achieving essential fresh qualities like extrudability, workability, open time, and buildability.
This study aims to an appropriate combination design for 3D printing geopolymer mortar using an inkjet technique similar to contour crafting (on a smaller scale). Furthermore, the fresh qualities of the mortar, namely its rheology and open-time, and its strength, are critical experimental variables to determine the optimal mixture design of the precursors, additives, activators, and w/b ratio. Finally, the requisite pumping pressure and printing speed for effective 3D printing were investigated. Considering the significance of geopolymer in terms of its performance in 3D printing and the scarcity of studies on this subject, as well as the findings of previous research, the overall goal is to propose a methodology for designing geopolymer concrete mixes suitable for 3D printing; the current research objectives are as follows: Examine the effect of fine aggregate size and type, binder type (slag or metakaolin) and ratio (slag: metakaolin), and alkaline solution amount and ratio (NaOH: Na2SiO3) on the specific setting time and mechanical strength development required by the 3D printing machine’s technical specifications; Optimize workability, extrudability, thixotropic open time, shape retention, and buildability for 3D printing.