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Matches in Ghent University Academic Bibliography for { <https://biblio.ugent.be/publication/01GTE5YZBYMDQ21DM3E6JCGFH8> ?p ?o. }

• 01GTE5YZBYMDQ21DM3E6JCGFH8 classification D1.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 promoter F4949240-F0ED-11E1-A9DE-61C894A0A6B4.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 promoter FA3817BC-F0ED-11E1-A9DE-61C894A0A6B4.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 date "2023".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 language "eng".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 type dissertation.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 hasPart 01GTE6AYQM3T0R8CZ85N1VWCB3.pdf.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 hasPart urn:uuid:64058a41-f695-4342-92f2-bb3ae64759f6.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 subject "Technology and Engineering".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 isbn "9789463556866".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 abstract "Concrete is intrinsically one of the greenest construction materials and is widely used in a myriad of applications. Also, concrete is one of the most economical, robust, easy-to-use and widely available materials around the world. It is estimated that the annual consumption of concrete is almost 25 gigatons. Even though the concrete itself is greener compared to other alternative construction materials, 8 % of the total global CO2 emission is caused by the cement and concrete industry. This is because of the tremendous use of concrete around the world. Therefore, one of the ways to reduce CO2 emissions is to minimize concrete consumption. In this regard, extrusion-based concrete 3D printing is a promising technology and has the potential to be a sustainable construction solution by utilizing structural optimization and reducing material usage. However, concrete mixtures used for 3D printing processes require a higher amount of binder and chemical admixtures to meet the stringent rheological requirements. Therefore, one of the main objectives of this thesis is to develop 3D printable concrete mixtures with lower environmental impact. This thesis outlines different strategies to improve the sustainability of 3D printable concrete mixtures. Sustainability can be improved by lowering the binder content and increasing the aggregate content, as the binder phase is the highest CO2-intensive phase. Also, the use of natural and recycled coarse aggregate in the granular skeleton can reduce the environmental impact. A set of 3D printable mixtures were developed with increasing aggregate content and changing the granular skeleton by incorporating natural and recycled coarse aggregates. However, such changes in the granular skeleton can influence the fresh and hardened state performance of the 3D printable mixtures. The increasing aggregate content resulted in increased plastic viscosity, yield stress, pumping pressure and also improved buildability. On the other hand, the incorporation of coarse aggregates and changing the granular skeleton reduced these parameters due to the lower specific surface area and better packing as the paste film thickness increased. Another strategy explored through the thesis is the use of a low CO2 alternative binder system for Portland cement. In this regard, 3D printable mixtures with calcium sulfoaluminate (CSA) cement were designed. Two major challenges for the mixtures with CSA cement were the extremely fast hydration and significantly high plastic viscosity compared to Portland cement. Using a suitable retarder, the rapid hydration was controlled, and the plastic viscosity was lowered by replacing part of the CSA cement with limestone powder. Though the use of a retarder was beneficial in providing the sufficient open time needed for the pumping phase, buildability was adversely affected due to the suppression of hydration. Using a two-stage mixing strategy, i.e., the hydration of a retarded CSA cement mixture with borax was re-initiated at the nozzle/print head with a static mixer, and the conflicting requirements for pumping and stiffening control were eliminated. To understand the extent of sustainability improvement by the abovementioned strategies, a detailed quantitative assessment of the environmental and economic impact of the 3D printable mixtures developed in this study for the production of one cubic meter volume was performed. 3D printable concrete mixtures satisfying a set of performance criteria were evaluated. Increasing the aggregate content decreases the environmental impact. However, incorporating natural and recycled coarse aggregates does not significantly reduce the environmental impact at a lower replacement level. The study provides insights into the environmental and economic impact of extrusion-based 3D concrete printing materials satisfying the same functional requirements. It was observed that the calcium sulfoaluminate-limestone binder systems have significantly lower global warming potential. However, the depletion of fossil resources indicator is much higher than the Portland cement-based mixtures. A significant portion of the material cost (even up to half of the cost) is contributed by the chemical admixtures in the 3D printable concrete mixtures, while the cost contribution by the chemical admixtures was much lower in the case of conventional mould-cast concrete mixtures. The thesis also focuses on the performance assessment of 3D printable concrete mixtures in fresh and hardened states. To assess the drying shrinkage a novel rheometer-based shrinkage measurement technique was developed. The method enables the measurement of shrinkage strains from the onset of preparation of the mixtures. It was found that the incorporation of about 3 wt% shrinkage-reducing agents significantly reduces the early-age shrinkage strain. The effect of early-age drying-induced pore structure changes was investigated using mercury intrusion porosimetry (MIP), loss on ignition and electrical resistivity measurements. When subjected to early-age drying, the porosity of the samples was found to increase significantly, and the assessment of chemically bound water revealed that the degree of hydration was not uniform but varied as a gradient, with the minimum occurring at the drying surface. Also, other shrinkage mitigating strategies were explored, which include the use of polypropylene fibers and the use of coarse aggregates. The effect of polypropylene fibers, shrinkagereducing agent and incorporation of natural or recycled coarse aggregates on the shrinkage cracking potential was assessed by restrained ring tests. The mixtures with the shrinkage-reducing agent and coarse aggregates prolong the time for cracking significantly due to the reduced shrinkage strain, while the addition of fibers increases the time to cracking marginally by enhancing the tensile strength of the mixtures. The study also focused on the porosity and pore structure of 3D-printed concrete elements, as the durability of the concrete is closely linked to its pore structure. The porosity characterisation was done with MIP and X-ray computed micro-tomography (X-ray μCT). Using the MIP data, surface fractal dimension and tortuosity parameters were calculated. It was observed that the CSA-limestone blended system has higher pore complexity and tortuosity than the Portland cement-slag blended mixture. The study revealed that the interlayer region contains larger and interconnected pores with low tortuosity, which could lead to enhanced transport of ions. Significantly higher open porosity and the presence of elongated pores with a high aspect ratio were observed in the interlayer compared to the bulk region. Also, the durability performance of the 3D printable mixtures was assessed by measuring the resistance against chloride migration and salt scaling. It was observed that the chloride migration coefficients were higher due to interconnected pores at the interlayer region and the application of fresh cement paste between the layers enhances the resistance to chloride migration. 3D-printed concrete elements showed much higher resistance to salt scaling as compared to mould-cast concrete due to the compensation of the glue spall stress by suction created from the ice formation at the interlayers. The practical feasibility of one of the most promising 3D printable mixtures developed was demonstrated by 3D printing a 1:4 scale breakwater element (8 kN weight). From the static mechanical tests, it was observed that the peak load at failure of the 3D printed breakwater element was lower than that of a mould-cast breakwater element with the same shape and dimensions. Also, the hydraulic stability of the 3D printed breakwater units was assessed and compared with a practically used breakwater element (ACCROBERMTM II) with wave flume tests at a 1:45 scale. The hydraulic performance of 3D printed breakwater elements was similar to that of the ACCROBERMTM II.".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 author C70F9076-914B-11E9-9F5B-CF1A5707D3EF.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 dateCreated "2023-03-01T08:52:29Z".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 dateModified "2024-11-28T00:06:54Z".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 name "Towards sustainable concrete 3D printing for marine structural applications".
• 01GTE5YZBYMDQ21DM3E6JCGFH8 pagination urn:uuid:dee13bfa-d62d-4cd0-a63a-91643d76bfa8.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 publisher urn:uuid:b00666ba-f790-4ebf-b82f-e1a5483d7fe2.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 sameAs LU-01GTE5YZBYMDQ21DM3E6JCGFH8.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 sourceOrganization urn:uuid:7d39dcf5-8600-4b15-8b61-16da8e47949e.
• 01GTE5YZBYMDQ21DM3E6JCGFH8 type D1.