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Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete
Mhene, T. 2025. Mechanical Characterisation and Compressive Creep of Recycled Aggregate Limestone Calcined Clay Cement Concrete. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/122d3fad-e2e6-4616-9af2-875469d9de55
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613759063719936 |
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| access_status_str | Open Access |
| author | Mhene, Tafadzwa Mthokozisi |
| author2 | Babafemi, Adewumi John |
| author_browse | Babafemi, Adewumi John Mhene, Tafadzwa Mthokozisi |
| author_facet | Babafemi, Adewumi John Mhene, Tafadzwa Mthokozisi |
| author_sort | Mhene, Tafadzwa Mthokozisi |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Mhene, T. 2025. Mechanical Characterisation and Compressive Creep of Recycled Aggregate Limestone Calcined Clay Cement Concrete. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/122d3fad-e2e6-4616-9af2-875469d9de55 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132610 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:14.564Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132610 Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete Mhene, Tafadzwa Mthokozisi Babafemi, Adewumi John Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. Cement -- Mechanical properties Limestone -- Biodegradation Concrete -- Creep Portland cement -- Additives UCTD Mhene, T. 2025. Mechanical Characterisation and Compressive Creep of Recycled Aggregate Limestone Calcined Clay Cement Concrete. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/122d3fad-e2e6-4616-9af2-875469d9de55 Thesis (MEng)--Stellenbosch University, 2025. ENGLISH ABSTRACT: Concrete is one of the most widely utilised materials in the construction of civil infrastructure, with a demand closely proportional to the demand of Portland cement (PC). However, PC production poses significant environmental challenges. An evolutionary technological breakthrough is the adoption of limestone calcined clay cement (LC³) composed of clinker, calcined kaolinite clay, limestone, and gypsum. While studies have investigated the mechanical and durability performance of LC³ at the paste and mortar levels, research on LC³ concrete under sustained compressive loadings is sparse. This study aims to characterise the quasi-static properties and time-dependent deformation behaviour of LC³ concrete under sustained compressive loadings. Additionally, to enhance sustainability, recycled fine aggregate (RFA) from construction and demolition waste (C&DW) replaced natural sand in LC³ concrete. The optimal replacement level was further analysed for time-dependent strain characteristics. To achieve this, a control PC concrete mix with a water-to-cement ratio of 0.55 was prepared, and 47.5% of PC was replaced by LC² constituents in a 2:1 calcined clay-to-limestone ratio, with an additional 2.5% gypsum included, to maintain sulphate levels. Polypropylene (PP) fibres were added at 1% by volume, creating a fibre-reinforced (FR) LC³ mix, while RFA was substituted for natural sand in LC³ concrete to create 25%, 50%, and 100% RFA-LC³ mixtures. A polycarboxylate ether (PCE) liquid based superplasticiser (SP) was dosed at 1% by the binder mass across all mixtures to enhance workability. In total, six concrete mixtures were tested, which are PC, LC³, FR-LC³, 25% RFA-LC³, 50% RFA-LC³, and 100% RFA-LC³. Workability, fresh density, setting time, and air content were assessed for each mixture. LC³-based mixtures generally show shorter setting times than PC, and workability decreases with higher RFA levels and PP fibre addition. FR-LC³ concrete exhibits higher air content than other mixtures, while RFA substitutions show a decreasing trend in air content with higher RFA levels. The compressive strength of water-cured LC³ concrete is comparable to PC concrete at 28 days. However, FR-LC³ concrete has the lowest compressive strength compared to other mixtures. Notably, 100% RFA-LC³ concrete has a compressive strength similar to PC concrete at 28 days. Flexural strengths of LC³ concrete are greater than those of PC concrete, with PP fibres significantly enhancing this property in LC³ concrete. Splitting tensile strengths of LC³ concrete are comparable to PC concrete, following the same trend as compressive strength. Although 25% RFA-LC³ concrete initially exhibits lower flexural and tensile strength than LC³ concrete and PC concrete, both strength properties increase with higher RFA replacement levels, with 100% RFA-LC³ demonstrating the highest flexural strength at 90 days. The modulus of elasticity across all mixtures follows the same trend as the compressive strength trends after 28 days of curing. Microstructural analysis (SEM and EDS) validates the agreement between the mechanical and microstructural properties of the mixtures. LC³ concrete exhibits lower drying shrinkage than PC concrete, with 100% RFA-LC³ concrete exhibiting the lowest shrinkage throughout the testing period. In FR-LC³ concrete, PP fibres initially increase shrinkage for the first 35 days, after which shrinkage strains drop below those of unreinforced LC³ concrete. The 100% RFA-LC³ concrete mixture exhibits a higher creep compliance at 50% stress level than the other concrete mixtures. In conclusion, LC³ concrete has a comparable mechanical performance to PC concrete, with enhanced performance in drying shrinkage and creep compliance, making it a suitable alternative in construction. These findings provide a benchmark for comparison to future research on the creep of LC³ concrete, particularly for concrete made with calcined kaolinite clays from South Africa. Further studies should focus on modelling the creep of LC³ concrete for long-term performance, for example, 50 years or more (100 years), field-scale testing, tensile creep, flexural creep of LC³ concrete at stress levels above 50%, and life cycle assessment of LC³ concrete with RFA from C&DW to promote a circular economy. AFRIKAANSE OPSOMMING: Beton bly een van die mees gebruikte materiale in siviele infrastruktuur, met 'n vraag wat nou eweredig is aan die vraag na Portland-sement (PC). PC-produksie hou egter aansienlike omgewingsuitdagings in. 'n Evolusionêre tegnologiese deurbraak is die aanvaarding van kalksteen gekalsineerde klei sement (LC3) wat bestaan uit klinker, gekalsineerde kaoliniet klei, kalksteen en gips. Terwyl studies die meganiese en duursaamheidsprestasie van LC3 op die pasta- en mortelvlak beoordeel het, is daar 'n gebrek aan literatuur oor die kruip van LC3-beton. Hierdie studie het ten doel om die kwasi-statiese eienskappe en tydafhanklike vervorming van LC3-beton onder volgehoue drukladings te ondersoek. Om volhoubaarheid te verbeter, het herwinde fyn aggregaat (RFA) van konstruksie- en slopingsafval (C&DW) natuurlike sand in LC3-beton vervang. Die optimale vervangingsvlak is verder ontleed vir tydafhanklike stameienskappe. Om dit te bereik, is 'n kontrole-PC-betonmengsel met 'n water-tot-sement-verhouding van 0,55 voorberei, en 47,5% van PC is vervang deur LC3-bestanddele in 'n 2:1 gekalsineerde klei-tot-kalksteen-verhouding, met 'n bykomende 2,5% gips ingesluit, om sulfaatvlakke te handhaaf. PP-vesels is teen 1% per volume bygevoeg, wat 'n veselversterkte (FR) LC3-mengsel geskep het, terwyl RFA vervang is met natuurlike sand in LC3-beton om 25%, 50% en 100% RFA-LC3-mengsels te skep. 'n Polikarboksilaateter (PCE) vloeistofgebaseerde superplastiseerder (SP) is teen 1% per volume oor alle mengsels gedoseer om werkbaarheid te verbeter. In totaal is ses betonmengsels getoets, wat PC, LC3, FR-LC3, 25% RFA-LC3, 50% RFA-LC3 en 100% RFA-LC3. Werkbaarheid, vars digtheid, stoltyd en luginhoud is vir elke mengsel beoordeel. LC3-gebaseerde mengsels toon oor die algemeen korter insteltye as rekenaar, en werkbaarheid neem af met hoër RFA-vlakke en PP-veseltoevoeging. FR-LC3-beton vertoon hoër luginhoud as ander mengsels, terwyl RFA-vervangings 'n dalende neiging in luginhoud met hoër RFA-vlakke toon. Die druksterkte van watergeharde LC3-beton is vergelykbaar met PC-beton op 28 dae. FR-LC3 het egter die laagste druksterkte in vergelyking met ander mengsels. Veral, 100% RFA-LC3 het 'n druksterkte soortgelyk aan dié van PC op 28 dae. Buigsterktes van LC3-beton is oor die algemeen hoër as dié van PC, met PP-vesels wat hierdie eienskap in LC3 aansienlik verbeter. Splitsingstreksterktes van LC3-beton is vergelykbaar met PC-beton, volgens dieselfde neiging as druksterkte. Alhoewel 25% RFA-LC3 aanvanklik laer buig- en treksterkte vertoon as LC3 en PC, neem albei sterkte-eienskappe toe met hoër RFA-vervanging vlakke, met 100% RFA-LC3 wat die hoogste buigsterkte op 90 dae toon. Die elastisiteitsmodulus oor alle mengsels volg dieselfde neiging as die druksterkteneigings na 28 dae van uitharding. Mikrostrukturele analise (SEM en EDX) bevestig die ooreenkoms tussen die meganiese en mikrostrukturele eienskappe van die mengsels. LC3-beton vertoon laer droogkrimp as PC, met 100% RFA-LC3 wat die laagste krimp gedurende die toetsperiode toon. In FR-LC3 verhoog PP-vesels aanvanklik krimping vir die eerste 35 dae, waarna krimpstamme onder dié van onversterkte LC3 daal. Drukdroogkruip by 30% en 50% stresvlakke volg 'n soortgelyke patroon as droogkrimp. 100% RFA-LC3 vertoon 'n hoër kruipnakoming by 50% spanningsvlak as die ander betonmengsels, wat dui op verskillende meganismes wat kruip by verhoogde spanningsvlakke beheer in vergelyking met krimp. Ten slotte, LC3-beton het 'n vergelykbare meganiese werkverrigting as rekenaar, met verbeterde werkverrigting in droogkrimp en kruipnakoming, wat dit 'n geskikte alternatief in konstruksie maak. Hierdie bevindings bied 'n maatstaf vir vergelyking met toekomstige navorsing oor die kruip van LC3-beton, veral vir beton wat met gekalsineerde kaolinietklei uit Suid-Afrika gemaak is. Verdere studies moet fokus op die modellering van die kruip van LC3-beton vir langtermynprestasie, byvoorbeeld 50 jaar of meer (100 jaar), veldskaaltoetsing, trekkruip, buigkruip van LC3-beton by spanningsvlakke bo 50%, en lewensiklusbeoordeling van LC3-beton met RFA van C&DW om 'n sirkulêre ekonomie te bevorder. Masters 2025-06-11T13:27:54Z 2025-06-11T13:27:54Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132610 en Stellenbosch University xxii, 167 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Cement -- Mechanical properties Limestone -- Biodegradation Concrete -- Creep Portland cement -- Additives UCTD Mhene, Tafadzwa Mthokozisi Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete |
| title | Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete |
| title_full | Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete |
| title_fullStr | Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete |
| title_full_unstemmed | Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete |
| title_short | Mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete |
| title_sort | mechanical characterisation and compressive creep of recycled aggregate limestone calcined clay cement concrete |
| topic | Cement -- Mechanical properties Limestone -- Biodegradation Concrete -- Creep Portland cement -- Additives UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132610 |
| work_keys_str_mv | AT mhenetafadzwamthokozisi mechanicalcharacterisationandcompressivecreepofrecycledaggregatelimestonecalcinedclaycementconcrete |