Rheo-mechanical, hardened mechanical characterisation, and tensile creep of limestone calcined clay cement fibre-reinforced printed concrete (LC3-FRPC)

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dc.contributor.advisorBabafemi, Adewumi Johnen_ZA
dc.contributor.advisorVan Zijl, Gideon P. A. G.en_ZA
dc.contributor.authorIbrahim, Kamoru Ademolaen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Civil Engineeringen_ZA
dc.date.accessioned2023-10-30T15:01:02Zen_ZA
dc.date.accessioned2024-02-20T10:32:28Zen_ZA
dc.date.available2023-10-30T15:01:02Zen_ZA
dc.date.available2024-02-20T10:32:28Zen_ZA
dc.date.issued2023-10en_ZA
dc.descriptionThesis (PhD)--Stellenbosch University, 2023.en_ZA
dc.description.abstractENGLISH ABSTRACT: Concrete is a widely used and acceptable civil engineering construction material. It contributes significantly to infrastructural development and global economic growth. However, its major challenge is its vulnerability to environmental degradation, pollution, carbon emissions, and cracking, which have detrimental influence on the sustainability of its applications under high demand, low recycling rates, and loading. The scarcity of raw materials, caused by wastage, overuse, and environmental issues, threatens infrastructural development. Hence, research on an emerging technology named 3D printed concrete (3DPC) to reduce waste, but also time and cost associated with the construction of concrete infrastructure is imperative. 3DPC is an evolving construction method and has been proposed as an alternative and environmental-friendly construction method to traditional construction method. The high cement content required for the 3D extrusion process is being reduced by partial replacement with supplementary cementitious materials (SCMs) such as fly ash, slag, and silica fume. However, these SCMs are limited in volume and do not have global spread, implying an urgent need for alternatives, but also care for the longevity of infrastructure. Limestone calcined clay cement (LC3) is a suitable SCM for sustainable concrete because of its global availability and comparable early and later strength gain, as recommended by previous studies. When polypropylene fibres are added to the mix, control of plastic shrinkage cracks, increased toughness, and reduced brittleness of 3DPC can be achieved. The main goal of this study is to investigate the rheology, hardened mechanical properties, and tensile creep of fibre-reinforced 3DPC containing LC3 (LC3-FRPC) by quantifying its layer deformation, but also the orthogonal interlayer bond deformation at different stress levels under sustained loadings. To achieve the goal stated above, this research develops the material mix design satisfying 3DPC requirements for early strength and stiffness, shrinkage cracking resistance and mechanical properties, including interfacial bond. The rheology and hardened mechanical properties of LC3-FRPC were compared to that of the fly ash-based counterpart (FA-FRPC). The strategy for strengthening the interfacial bond of LC3-FRPC with effective microorganisms (EM), which enhances not only the bond strength but also improves mechanical capacities are presented. The mechanical responses were verified by microstructural analysis through scanning electron microscopy augmented by energy-dispersive X-ray spectroscopy and X-ray computed tomography to assess the hydration products of the blended binders and the self-healing action of LC3 and EM in FRPC. Then, the creep and shrinkage deformations in two orthogonal directions, and other parameters associated with creep responses, including creep fracture are also conducted experimentally on LC3-FRPC. The creep specimens were subjected to sustained stresses of 40, 60, and 80% of the direct tensile strength, and 40% of the flexural strength results obtained from the quasi-static tests. The results revealed that FRPC mixtures tested showed good rheological properties, with LC3-FRPC showing improved the workability, open time, and buildability by 1.7%, 15.4%, and 19%, respectively, compared to FA-FRPC. FA-FRPC outperformed LC3-FRPC in compression, tension, and flexure because of its lower water demand, but the bond strength between the interfacial layers is higher in LC3-FRPC than in FA-FRPC, with an increase of 8.1% for tension and 9.8% for flexure. EM-enhanced LC3-FRPC had significantly higher bond strengths than the reference LC3-FRPC in both direct tension (26.1%) and flexure (33.7%), thereby implying a lower level of anisotropy. The effects of the binders, particularly the LC3 and the EM on the strengths of FRPC and the macropores at the interfaces of printed concrete, improved the material by forming more calcite crystals. Finally, for the creep response under sustained loadings, none of the LC3-FRPC specimens fractured in tension and flexure. Instead, higher direct tensile and flexural strengths were recorded for the creep specimens after 225 days loaded at different stress levels.en_ZA
dc.description.abstractAFRIKAANS OPSOMMING: Beton is 'n wyd gebruikte en aanvaarbare boumateriaal vir siviele ingenieurswese. Dit dra aansienlik by tot infrastruktuurontwikkeling en globale ekonomiese groei. Die grootste uitdaging daarvan is egter sy kwesbaarheid vir agteruitgang weens omgewingsblootstelling, besoedeling, koolstofvrystellings en krake, wat 'n nadelige invloed op die volhoubaarheid van sy toepassings onder hoë aanvraag, lae herwinningsyfers en belasting het. Die skaarste aan grondstowwe, wat veroorsaak word deur vermorsing, oorbenutting en omgewingskwessies, bedreig infrastruktuurontwikkeling. Daarom is navorsing oor 'n opkomende tegnologie genaamd 3D-gedrukte beton (3DPC) noodsaaklik om vermorsing te verminder, maar ook tyd en koste verbonde aan die konstruksie van beton infrastruktuur. 3DPC is 'n ontwikkelende konstruksiemetode en is voorgestel as 'n alternatiewe en omgewingsvriendelike konstruksiemetode tot tradisionele konstruksiemetode. Die hoë sementinhoud wat vir die 3D-ekstrusieproses benodig word, word verminder deur gedeeltelike vervanging met aanvullende sementmateriaal (SCM's) soos vliegas, slagment en silika-dampe. Hierdie SCM's is egter beperk in volume en is nie wêreldwyd verspreid nie, wat 'n dringende behoefte aan alternatiewe impliseer, maar sorg ook vir die lang lewe van infrastruktuur. Kalksteengebrande kleisement (LC3) is 'n geskikte SCM vir volhoubare beton vanweë die globale beskikbaarheid en vergelykbare vroeë en latere sterktetoename, soos aanbeveel deur vorige studies. Wanneer polipropileenvesels by die mengsel gevoeg word, kan plastiese krimpkrake beheer word, en verhoogde taaiheid en verminderde brosheid van 3DPC bereik word. Die hoofdoel van hierdie studie is om die reologie, verharde meganiese eienskappe en trekkruip van veselversterkte 3DPC wat LC3 bevat (LC3-FRPC) te ondersoek deur die laagvervorming daarvan te kwantifiseer, maar ook die ortogonale tussenlaagbindingsdeformasie by verskillende spanningsvlakke onder volgehoue belastings. Om die doel hierbo genoem te bereik, ontwikkel hierdie navorsing die materiaalmengselontwerp wat voldoen aan 3DPC vereistes vir vroeë sterkte en styfheid, krimpkraakweerstand en meganiese eienskappe, insluitend intervlak verbandsterkte. Die reologie en verharde meganiese eienskappe van LC3-FRPC is vergelyk met dié van die vliegas-gebaseerde eweknie (FA-FRPC). Die strategie vir die versterking van die intervlak verband van LC3-FRPC met effektiewe mikroörganismes (EM), wat nie net die bindingssterkte verbeter nie, maar ook meganiese kapasiteit verbeter, word aangebied. Die meganiese gedrag is geverifieer deur mikrostrukturele analise deur skandeerelektronmikroskopie aangevul deur energie-verspreidende X-straalspektroskopie en X-straal rekenaartomografie om die hidrasie produkte van die gemengde binders en die selfgenesende aksie van LC3 en EM in FRPC te assesseer. Dan word die kruip- en krimpdeformasies in twee ortogonale rigtings, en ander parametermetings wat met kruipgedrag, insluitend kruipbreuk geassosieer word, ook eksperimenteel op LC3-FRPC uitgevoer. Die kruipmonsters is onderwerp aan volgehoue spannings van 40, 60 en 80% van die direkte treksterkte, en 40% van die buigsterkte-resultate verkry uit die kwasistatiese toetse. Die resultate het aan die lig gebring dat FRPC-mengsels wat getoets is, goeie reologiese eienskappe getoon het, met LC3-FRPC wat die werkbaarheid, ooptyd en boubaarheid met onderskeidelik 1.7%, 15.4% en 19% verbeter het in vergelyking met FA-FRPC. FA-FRPC het beter gevaar as LC3-FRPC in druk, trek en buiging vanweë sy laer wateraanvraag, maar die verbandsterkte tussen die gedrukte lae is hoër in LC3-FRPC as in FA-FRPC, met 'n toename van 8.1% vir trek en 9,8% vir buiging. EM-versterkte LC3-FRPC het aansienlik hoër verbandsterktes as die verwysing LC3-FRPC in beide direkte trek (26.1%) en buiging (33.7%), wat 'n laer vlak van anisotropie impliseer. Die uitwerking van die binders, veral die LC3 en die EM op die sterkpunte van FRPC en die makroporieë by die intervlakke van gedrukte beton, het die materiaal verbeter deur meer kalsietkristalle te vorm. Ten slotte, vir die kruipgedrag onder volgehoue belasting, het geen van die LC3-FRPC monsters in trek en buiging gebreek nie. In plaas daarvan is hoër direkte trek- en buigsterktes aangeteken vir die kruipmonsters na 225 dae gelaai by verskillende spanningsvlakke.en_ZA
dc.description.versionDoctoralen_ZA
dc.embargo.terms2024-06-30en_ZA
dc.format.extentxxxi, 232 pages : illustrationsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/129408en_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch University
dc.subject.lcshThree-dimensional printingen_ZA
dc.subject.lcshConcrete construction industryen_ZA
dc.subject.lcsh3D concrete printingen_ZA
dc.subject.lcshConcrete -- Service lifeen_ZA
dc.titleRheo-mechanical, hardened mechanical characterisation, and tensile creep of limestone calcined clay cement fibre-reinforced printed concrete (LC3-FRPC)en_ZA
dc.typeThesisen_ZA
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