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Matches in Ghent University Academic Bibliography for { <https://biblio.ugent.be/publication/01J0NRC8R6B5WV36NE7AZQJSP4> ?p ?o. }

• 01J0NRC8R6B5WV36NE7AZQJSP4 classification D1.
• 01J0NRC8R6B5WV36NE7AZQJSP4 promoter F4949240-F0ED-11E1-A9DE-61C894A0A6B4.
• 01J0NRC8R6B5WV36NE7AZQJSP4 promoter FA3817BC-F0ED-11E1-A9DE-61C894A0A6B4.
• 01J0NRC8R6B5WV36NE7AZQJSP4 promoter urn:uuid:72ee8de0-2e4e-4f4c-a247-212e51ec6aab.
• 01J0NRC8R6B5WV36NE7AZQJSP4 date "2024".
• 01J0NRC8R6B5WV36NE7AZQJSP4 language "eng".
• 01J0NRC8R6B5WV36NE7AZQJSP4 type dissertation.
• 01J0NRC8R6B5WV36NE7AZQJSP4 hasPart 01J0NRRMS06QE2X9M0XPJY7JXB.pdf.
• 01J0NRC8R6B5WV36NE7AZQJSP4 hasPart urn:uuid:2ef37ce6-a1cf-4487-a322-35176847ff08.
• 01J0NRC8R6B5WV36NE7AZQJSP4 subject "Technology and Engineering".
• 01J0NRC8R6B5WV36NE7AZQJSP4 abstract "With the proposal of “carbon peak” and “carbon neutrality”, as well as the aging of the population, the transformation of the construction industry towards energy efficiency and automation is imperative. 3D concrete printing technology can realize highly automated construction, which can empower the transformation and upgrading of the construction industry. Currently, the widespread adoption of 3D concrete printing technology is primarily hindered by the limited availability of suitable printable materials, despite the advancements in automation technology. To advance the application and development of 3D concrete printing technology, there is an urgent need to conduct systematic and in-depth research on the design theory, performance evaluation and performance control of materials for 3D printing. Cement-based materials, as the main building materials for extrusion-based 3D concrete printing technology, encounter some challenges that still require resolution. During the printing process, 3D printed cement-based materials (3DPCM) are extruded and deposited layer by layer to form components or buildings in the absence of formwork support and vibratory compaction. Consequently, it poses challenges in the evaluation and control for rheological properties of 3DPCM. Simultaneously, this process inevitably introduces interlayer interfaces in the printed object. It has been demonstrated that the introduced interlayer interface zones are porous and is weak areas in terms of mechanical properties and durability. However, the formation mechanism of interlayer interface zones is not clear yet. In addition, owing to the lack of formwork protection, the performance of 3DPCM becomes sensitive to environmental conditions. Nevertheless, there is a notable scarcity of research on how environmental factors affect the rheological properties and interlayer interface characteristics of 3DPCM. Beyond just considering pores, studying the distribution characteristics of physical phases such as aggregates and hydration products along with their influencing factors is crucial. This would significantly contribute to a comprehensive and deep understanding of the interlayer interface zone, providing insights into its formation mechanisms. Furthermore, it holds great significance in optimizing the interlayer interface zone. Investigating the impact of temperature on the rheological properties and interlayer interface characteristics of 3DPCM can establish a scientific foundation for 3DPCM mix design, performance control, and its application in various environments. Therefore, this research focuses on the rheological properties and layer interface characteristics of 3DPCM, mainly from the following four aspects. Firstly, rheology and ultrasonic transmission methods were employed to comprehensively characterize the structural build-up behavior of 3DPCM. The concepts and calculation methods of the ultimate layer thickness and ultimate printing velocity were proposed, quantitatively characterizing and predicting the printing shape stability and printing efficiency of 3DPCM. Secondly, the phase distribution at the layer interface of 3DPCM was characterized. The influence mechanism of printing height, time interval, cementitious material components on the phase distribution at the interface zone and interlayer adhesion were studied. Furthermore, the formation process and mechanism of the interface between layers were elucidated. Thirdly, the study systematically examined the rheological response mechanism of 3DPCM under varying temperatures. The validation tests for feasibility of active rheology control for 3DPCM based on the coupling of temperature and viscosity modifier were carried out. Fourthly, the phase distribution and components at the layer interface zone of hardened 3DPCM at different temperatures were characterized. The interlayer adhesion properties of 3DPCM after hardening at different temperatures and the influence mechanism of temperature on the layer interface zone were analyzed. The main research findings are as follows: (1) An evaluation method for structural build-up behaviour of 3DPCM is established. The concepts and calculation methods for ultimate layer thickness and printing velocity are proposed, enabling a quantitative correlation between rheological parameters and printing parameters. The instantaneous response and time evolution of different types of redispersible polymer powder (RDP) to the structural build-up of 3DPCM were investigated for the first time based on dynamic and static shear tests. The ultimate layer thickness and printing velocity of 3DPCM are calculated based on dynamic and static yield stresses. It resulted in quantitative characterization of shape stability and printing efficiency of 3DPCM. The results indicate that the progression of shear modulus aligns with the trend observed in ultrasonic pulse velocity, which can be used to characterize the structuration rate of 3DPCM. The effects of RDP on the structural build-up of 3DPCM are affected by the presence or absence of hydroxypropyl methylcellulose ether. Polyvinyl acetateethylene based RDP synthesized with lower ethylene monomer content can improve the shape stability of 3DPCM after extrusion. When its dosage is 4%, the ultimate layer thickness of 3DPCM increased by 203.3% compared with that of blank group. Meanwhile, this RDP can improve the printing efficiency of 3DPCM with HPMC. (2) The phase distribution characteristics at the interlayer interface zone of 3DPCM are revealed. The correlation between these features and interlayer adhesion performance is clarified. Additionally, the formation mechanism of the layer interface zone is elucidated. Compared to the matrix, the layer interface zone exhibits higher porosity and larger pores. The increase in yield stress of 3DPCM tends to weaken the adhesion between layers, resulting in an increase in porosity and pore size. Aggregates are distributed far away from the interface zone owing to the wall effect of particle accumulation, bringing a reduction in the aggregate volume fraction of the layer interface zone compared with the matrix. This thereby weakens the interlocking effect of aggregates. The material deformation and aggregate settlement during printing promote the redistribution of aggregates and pores, causing a decrease in the discrepancy of the aggregate volume fraction and porosity between the interlayer interface zone at the bottom of the sample and the matrix. It also contributes to an increase in this discrepancy between the interlayer interface area and the matrix at the top of the sample. The variation in phase distribution with the printing height, further causes the interlayer bond strength to decrease as the printing height increases. The large number of pores at the interlayer interface zone, coupled with the moisture migration caused by humidity differences and aggregate settlement, provide conditions for the growth and enrichment of calcium hydroxide (CH) at the interlayer interface zone. As the time interval increases, the yield stress of the underlying material increases, accompanied by an increase in the amount of evaporated water. This weakens the adhesion between layers, leading to escalation in pore content, pore size, and the amount of unhydrated cement clinker and CH at the layer interface zone. Prolonged time interval even results in the occurrence of cold cracks in this zone. As a result, the interlayer bond strength of 3DPCM decreases with increasing time interval. (3) The influence law and mechanism of silica fume and ultra-fine fly ash on the phase distribution of layer interface zone and interlayer adhesion are ascertained. Silica fume (SF) enhances the yield stress and structuration rate of 3DPCM, leading to increased deformation resistance and weakened aggregate settlement. As a result, the phase distribution in the interfacial region of 3DPCM is more continuous. This improves the interlayer bond strength and reduces its variation with printing height. SF not only improves the water retention of 3DPCM, but also reduces the CH content at the layer interface zone, due to its high specific surface area and secondary hydration effect. It further strengthens the uniform distribution of hydration products near the layer interface of 3DPCM and reduces the sensitivity of the interlayer bond strength to the time interval. Ultrafine fly ash (UFA) delays cement hydration and reduces the structuration rate of 3DPCM, intensifying the deformation of the bottom layer of the sample and the settlement of the aggregate. This in turn leads to a significant increase in the porosity, while a remarkable decrease in the aggregate content of the interface zone between the top layers of 3DPCM. The deteriorating effect of UFA on the homogeneity of phase distribution at the layer interface zone also causes a decrease in interlayer bond strength of 3DPCM with printing height. Simultaneously, the incorporation of UFA decreases the formation rate of irreversible structures in 3DPCM, reducing the loss of the interlayer bond strength with increasing time interval. (4) The rheological response of 3DPCM to different temperatures and its mechanism are clarified. The active rheology control of 3DPCM based on the coupling of temperature and viscosity modifier is proposed and verified. As the temperature increases from 5 °C to 40 °C, the apparent viscosity of 3DPCM decreases due to the decrease in the viscosity of water and the enhancement of the Brownian motion of particles. The adsorption of hydroxypropyl methylcellulose (HPMC) on the cement surface strengthens particle flocculation and interparticle friction, which reduces the temperature dependence of the apparent viscosity of 3DPCM. The adsorption of polycarboxylate ether-based water reducer (PCE) prevents particle flocculation, thus increasing the sensitivity of the apparent viscosity of 3DPCM at low temperature. The thixotropic area of 3DPCM with incorporated HPMC and PCE monotonically decreases with increasing temperature due to the inhibition of hydration. With increasing temperature, higher dosage of PCE initially decreases the energy storage modulus and static yield stress of 3DPCM due to the enhanced adsorption and steric hindrance effect of PCE. Temperature control mainly affects the dissolution of HPMC and PCE and their adsorption behavior on the surface of cement particles, which in turn alters the rheological response of the 3DPCM. Printing tests confirm that appropriately elevated temperatures can improve the buildability of 3DPCM with HPMC, while this has little effect on the extrudability of 3DPCM. (5) The effects and mechanisms of temperature on the phase distribution characteristics and adhesion properties of the interlayer interface are revealed. High-temperature curing at early age improves the rate and degree of structuration in cement paste and mitigates the aggregate settlement. This thereby improves the uniformity of aggregate distribution and reduces the variations in aggregate volume fraction at the interface zone. High-temperature curing promotes the rapid generation of hydration products, thereby refining the pore diameter and reducing the pore volume at the interlayer interface zone of 3DPCM. Meanwhile, high-temperature curing increases the amount of high-density CSH (HD-CSH) at the interlayer interface zone, hence increasing the average elastic modulus of hydration products. Hightemperature curing also reduces the distribution ranges of atomic ratios, including Si/Ca, Al/Ca and S/Ca of hydration products at the interlayer interface zone of 3DPCM. The curing condition also narrows down the distribution range of the elastic modulus of hydrates at the interlayer interface zone. The improvement in the distribution homogeneity of aggregates, pores and hydration products caused by hightemperature curing contributes to the increase in interlayer bond strength of 3DPCM. Short-term high-temperature curing, while taking measures to prevent water evaporation loss, improves the long-term interlayer bond strength of 3DPCM.".
• 01J0NRC8R6B5WV36NE7AZQJSP4 author ee2cac08-2ade-11ec-9175-915b01dfdd17.
• 01J0NRC8R6B5WV36NE7AZQJSP4 dateCreated "2024-06-18T13:25:29Z".
• 01J0NRC8R6B5WV36NE7AZQJSP4 dateModified "2024-11-28T00:02:41Z".
• 01J0NRC8R6B5WV36NE7AZQJSP4 name "Research on rheological properties and interlayer interface characteristics of 3D printed cement-based materials".
• 01J0NRC8R6B5WV36NE7AZQJSP4 pagination urn:uuid:59930104-3906-4410-8346-c5b730b2f44b.
• 01J0NRC8R6B5WV36NE7AZQJSP4 publisher urn:uuid:33d6a424-8d16-4e69-8f7c-f6106e6729dc.
• 01J0NRC8R6B5WV36NE7AZQJSP4 sameAs LU-01J0NRC8R6B5WV36NE7AZQJSP4.
• 01J0NRC8R6B5WV36NE7AZQJSP4 sourceOrganization urn:uuid:98241d0a-cb27-4b07-aefb-4a4ad283818b.
• 01J0NRC8R6B5WV36NE7AZQJSP4 type D1.