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Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction
Thesis (MEng)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867613920025378816 |
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| access_status_str | Open Access |
| author | Steyn, Kari |
| author2 | Babafemi, John Babafemi |
| author_browse | Babafemi, John Babafemi Steyn, Kari |
| author_facet | Babafemi, John Babafemi Steyn, Kari |
| author_sort | Steyn, Kari |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134831 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:43:48.089Z |
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| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134831 Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction Steyn, Kari Babafemi, John Babafemi De Villiers, Wibke Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. Carbon sequestration Sustainable buildings -- Design and construction Building materials -- Testing Thesis (MEng)--Stellenbosch University, 2025. Steyn, K. 2025. Mechanical, Durability and Carbon Sequestration Performance of Hempcrete for Carbon-Negative Construction. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/73274da9-77a3-4910-804e-d487ce26bb88 ENGLISH ABSTRACT: In view of the significant contribution of the construction industry to global greenhouse gas emissions, a growing imperative for environmentally responsible construction practices has been recognised, consequently prompting heightened scholarly interest in the development of sustainable construction materials. Within this context, hempcrete has garnered significant interest due to its carbon-negative attributes, enabling dual pathways for carbon sequestration through both photosynthesis mechanisms, during hemp plant growth, and binder carbonation processes over the material’s lifecycle. In addition, hempcrete exhibits favourable hygrothermal properties, demonstrates inherent fire resistance and is resistant to mould and insects. Hence, demonstrating both environmental and functional potential, hempcrete has emerged as a promising alternative for mitigating the environmental consequences of the construction industry and advancing efforts towards achieving net-zero climate targets. This study investigated the microstructural characteristics of constituent materials, mechanical properties, durability properties and the carbon sequestration potential of hempcrete, for the advancement of scientific knowledge and understanding of hempcrete and its practical applicability in the construction sector. Two hempcrete mix designs were developed and investigated to evaluate the influence of binder composition on the performance and properties of hempcrete. Specifically, the reference hempcrete mix design employed a lime and metakaolin binder, whilst the second incorporated a partial replacement of the binder with potassium sulphate. The experimental framework encompassed microstructural characterisation, including particle size distribution analysis, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray fluorescence spectrometry and inductively coupled plasma mass spectrometry. Mechanical properties were evaluated through density and compressive strength tests on ambient-cured and oven-dried hempcrete specimens. Durability tests included capillary water absorption, drying shrinkage and oxygen permeability index tests. Furthermore, the experimental framework addressed environmental performance through investigating the carbon sequestration potential of the developed hempcrete. The results demonstrated that a 3% replacement of the binder, by weight, with potassium sulphate (PS), notably enhanced the compressive strength performance of hempcrete specimens at all curing ages, whilst preserving the density and lightweight nature of the material. Specifically, the presence of PS enhanced the compressive strength by 50.47% and 99.73% at 7 and 14 days, respectively, whereas at 28 days, the compressive strength improved from 0.41 MPa to 0.68 MPa, corresponding to a 64.99% increase. In addition, the hempcrete developed in this study presented superior compressive strengths when compared to various bio-based building materials documented in existing literature, with particularly elevated performance recorded for hempcrete containing potassium sulphate (0.68 MPa). In terms of durability, potassium sulphate inclusion was observed to reduce the drying shrinkage of hempcrete and had no notable effects on the capillary water absorption behaviour relative to the reference mix design. Results demonstrated that the drying shrinkage was reduced from 0.344% to 0.247% through the inclusion of PS, while the 24-hour capillary water absorption coefficient associated with PS inclusion reflected a value of 0.09 kg/(m2s0.5) relative to the 0.08 kg/(m2s0.5) observed for the reference hempcrete formulation. Investigations into the oxygen permeability index of hempcrete specimens confirmed that the experimental procedure, originally developed for the evaluation of conventional concrete, was unsuitable for the assessment of highly permeable construction materials, such as the hempcrete investigated in this study. Carbon sequestration assessments demonstrated that the developed hempcrete has the capacity to sequester more CO2 than is emitted throughout its production, with REF and M1 presenting net-negative GHG emissions of -0.491 kg CO2e/specimen and -0.47 kg_CO2e/specimen, respectively. PS inclusion exerted a marginal influence on the carbon sequestration capacity of hempcrete specimens, thus confirming that PS exhibits considerable potential for enhancing hempcrete properties, while simultaneously preserving the environmental credentials of the material. Collectively, the observed improvements in compressive strength and reduction in drying shrinkage, associated with PS inclusion, address technical constraints and strengthen the suitability of hempcrete for implementation in mainstream construction applications. Furthermore, the preservation of negative net GHG emissions demonstrates that the hempcrete developed in this study aligns with emerging policy developments that prioritise the progression towards carbon-negative construction practices. AFRIKAANSE OPSOMMING: In die lig van die beduidende bydrae van die konstruksiebedryf tot globale kweekhuisgasvrystellings, is ‘n toenemende noodsaaklikheid vir omgewingsbewuste konstruksiepraktyke erken. Die gevolg is verhoogde wetenskaplike belangstelling in die ontwikkeling van volhoubare konstruksie materiaal. Binne hierdie konteks, het hempcrete aansienlik belangstelling gelok weëns die materiaal se koolstof-negatiewe eienskappe, waardeer tweeledige roetes vir koolstofsekwestrasie deur middel van fotosintesemeganismes, tydens hemp-plantgroei, en bindmiddelkarboneringsprosesse oor die materiaal se lewensiklus bewerkstellig word. Daarbenewens beskik hempcrete oor gunstige higrotermiese eienskappe, vertoon inherente brandweerstand, sowel as skimmel- en insekweerstand. Gevolglik het hempcrete, deur beide omgewings- en funksionele potensiaal te vertoon, as ‘n belowende alternatief na vore gekom vir die versagting van omgewingsgevolge van die konstruksiebedryf en die bevordering van pogings tot netto-nul klimaatsdoelwitte. Hierdie tesis ondersoek die mikrostrukturele kenmerke van samestellende materiale, meganiese eienskappe, duursaamheidseienskappe en die koolstofsekwestrasie potensiaal van hempcrete, vir die bevordering van wetenskaplike kennis en begrip van hempcrete sowel as die materiaal se praktiese toepaslikheid in die konstruksiebedryf. Twee hempcrete mengselontwerpe was ontwikkel en ondersoek om die invloed van bindmateriaal samestelling op die werkverrigting en eienskappe van hempcrete, te evalueer. Spesifiek, die verwysings hempcrete mengselontwerp het kalk en metakaolien as bindmateriaal gebruik, terwyl die tweede ‘n gedeeltelike vervanging van die bindmateriaal, met kaliumsulfaat, ingesluit het. Die eksperimentele raamwerk het mikrostrukturele karakteriseering ingesluit, insluitend deeltjiegroteverspreidingsontleding, skanderende elektronmikroskopie gekoppel aan energie-dispersiewe X-straalspektrometrie, X-straalfluoresserende ontleding en Induktief gekoppelde plasma-massaspektrometrie. Meganiese eienskappe was geëvalueer deur digtheid en druksterkte toetse op omgewing-geharde en oondgedroogte hempcrete toetsmonsters. Duursaamheidstoetse het kapillêre waterabsorpsie, droogkrimping en suurstofdeurlaatbaarheidsindeks toetse ingesluit. Bykomend, die eksperimentele raamwerk het die omgewingsprestasie aangespreek, deur die koolstofsekwestrasiepotensiaal van die ontwikkelde hempcrete te ondersoek. Die resultate het getoon dat ‘n 3% vervanging van die bindmateriaal, volgens massa, met kaliumsulfaat (PS), ‘n noemenswaardige verbetering in druksterkte prestasie van hempcrete toetsmonsters aangedui het, by alle verhardingstye, terwyl die digtheid en liggewig aard van die materiaal behoue gebly het. Spesifiek, die teenwoordigheid van PS het die druksterkte met 50.47% en 99.73% op 7 en 14 dae, onderskeidelik, verbeter, terwyl die drusterkte op 28 dae van 0.41 MPa tot 0.68 MPa verbeter het, wat ooreenstem met ‘n 64.99% verhoging. Daarby, het die ontwikkelde hempcrete hoër druksterkte getoon in vergelyking met verskeie bio-gebaseerde boumateriale wat gedokumenteer is in bestaande studies, met besonder verhoogde sterkte aangeteken vir hempcrete wat PS ingesluit het (0.68 MPa). In terme van duursaamheid, het die teenwoordigheid van PS die droogkrimping van hempcrete verminder en het geen noemenswaardige uitwerking op die kapillêre waterabsorpsie gedrag, relatief tot die verwysings hempcrete, gehad nie. Die resultate het aangetoon dat die droogkrimping van 0.344% tot 0.247% verminder was deur die insluiting van PS, terwyl die 24-uur kapillêre waterabsorpsie koëffisiënt, geassosieer met PS-insluiting, ‘n resultaat van 0.089 kg/(m2s0.5) weerspieël het, relatief tot die 0.082_kg/(m2s0.5) wat waargeneem is vir die verwysings hempcrete. Ondersoeke na suurstofdeurlaatbaarheidsindeks van hempcrete toetsmonsters, het bevestig dat die eksperimentele prosedure, wat aanvanklik vir die evaluering van konvensionele beton ontwerp is, ondoelmatig was vir die evaluasie van hoogs deurlaatbare konstruksiemateriale, soos die hempcrete ondersoek in hierdie studie. Koolstofsekwestrasie asseserings het gedemonstreer dat die ontwerpte hempcrete die vermoë het om meer CO2 te sekwestreer as wat vrygestel is tydens die produksie daarvan, met REF en M1 wat netto negatiewe GHG emissies van onderskeidelik -0.491 kg_CO2e/toetsmonster en -0.47 kg CO2e/toetsmonster toon. PS-insluiting het ‘n geringe invloed uitgeoefen op die koolstofsekwestrasie kapasiteit van hempcrete toetsmonsters, wat dus bevestig dat PS aansienlike potensiaal toon vir die verbetering van hempcrete eienskappe, terwyl dit terselfdertyd omgewingsprestasie van die materiaal behou. Gesamentlik, spreek die waargenome verbeterings in druksterkte en die afname in droogkrimping, wat aan die insluiting van PS toeskryfbaar is, die tegniese beperkings aan en verhoog die geskiktheid van hempcrete vir implementering in hoofstroomkonstruksiepraktyke. Hierbenewens toon die behoud van netto negatiewe GHG emissies dat die studie ontwikkelde hempcrete met opkomende beleidsraamwerke stook, wat die vordering na koolstof-negatiewe konstruksiepraktyke prioritiseer. Masters 2026-01-12T06:42:43Z 2026-01-12T06:42:43Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134831 Stellenbosch University xxv, 213 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Carbon sequestration Sustainable buildings -- Design and construction Building materials -- Testing Steyn, Kari Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction |
| title | Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction |
| title_full | Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction |
| title_fullStr | Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction |
| title_full_unstemmed | Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction |
| title_short | Mechanical, durability and carbon sequestration performance of hempcrete for carbon-negative construction |
| title_sort | mechanical durability and carbon sequestration performance of hempcrete for carbon negative construction |
| topic | Carbon sequestration Sustainable buildings -- Design and construction Building materials -- Testing |
| url | https://scholar.sun.ac.za/handle/10019.1/134831 |
| work_keys_str_mv | AT steynkari mechanicaldurabilityandcarbonsequestrationperformanceofhempcreteforcarbonnegativeconstruction |