Department of Civil Engineering

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Browsing Department of Civil Engineering by Subject "Additive manufacturing -- Automation."

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    Physico-chemical interventions for improved interlayer adhesion in 3D printable concrete.
    (Stellenbosch : Stellenbosch University, 2024-03) Munemo, Ruvimbo Eustina; Van Zijl, Gideon P. A. G.; Kruger, Jacques; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: 3D concrete printing (3DCP), a revolutionary additive manufacturing (AM) technique, has the potential to transform the construction industry. It is an advantageous technique that offers more geometric freedom while simultaneously promising resource efficiency and enhanced productivity. However, due to the layer-based intrinsic nature of ANL the lack of interlayer adhesion (IA) is a prevalent issue that significantly impacts the mechanical performance of printed structures. Although the mechanism leading to lack of IA between filament layer in 3D printable concrete (3DPC) have been investigated in literature, the synergistic and antagonistic nature of these mechanism• is rarely considered Weak adhesion bet-ween filament layers undermines the inherently advantageous properties of 3DPC, as well as those of the fabrication process. Therefore, to address this issue, this research endeavors to ascertain physico-chemical interventions to bolster IA between 3DPC filaments which do not impede the fabrication process. An extensive review of methods that have been Implemented to enhance interlayer bond strength (IBS) is conducted to elucidate beneficial characteristics and strategies that yield the most desirable IA. Furthermore, strategies employed for modelling the interlayer region (IR) are analysed and used as the foundation for determining ruling parameters in simulation of IBS. Subsequently, a rubric for selection and assessment of effectiveness of an intervention strategy is proposed. The principal selection criterion is that an intervention must enhance IA by leveraging intrinsic properties of 3DPC without hampering the efficiency of the fabrication process. Each intervention IS mechanically and microstructurally characterized and the mechanisms leading to IA enhancement are investigated Two interventions are proposed and implemented Both strategies are novel to the 3DCP industry but show great promise and reliability with a low degree of complexity in both accessibility and implementation. The first intervention, characterised by induction of thermo-hydrokinetics to improve surface malleability and moisture content through the incorporation of a short-lived localised burst of steam on the surface of the preceding filament layer prior to placement of the subsequent filament layer, is presented and rigorously tested to assess the Improvement in IA. The IBS is bolstered by 78 0/0. The Intervention is then evaluated against the pre-set criteria to validate whether it is viable technique for enhancing IBS. The behavior induced by this intervention leading to better IA is subsequently empirically and computationally modelled and analysed to illuminate the Influencing factors and how they contribute to the enhancement of IA. The proposed empirical model appears to be extendable as it was able to accurately simulate the results of other studies conducted m literature yielding statistically significant findings. The second intervention characterized by silicate impregnation in the IR via interfacial surface treatment, IS also presented and evaluated. It bolstered IBS by 103 0/0, as well as the bonded area, as evidenced by the enlarged failure area. This research is a comprehensive investigation into intervention strategies to mitigate the lack of IA, with proposed interventions that not only yield more robust IRS but are also viable techniques that can be seamlessly Integrated into the fabrication process. The findings encourage a more synergistic approach to ensure strategies amalgamate to create resilient structures.