The structural use of alkali activated materials (Geopolymers)
| dc.contributor.advisor | Boshoff, William Peter | en_ZA |
| dc.contributor.author | Louw, Joachim Paul | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. | en_ZA |
| dc.date.accessioned | 2017-02-08T11:26:54Z | |
| dc.date.accessioned | 2017-03-29T11:33:35Z | |
| dc.date.available | 2017-02-08T11:26:54Z | |
| dc.date.available | 2017-03-29T11:33:35Z | |
| dc.date.issued | 2017-03 | |
| dc.description | Thesis (MEng)--Stellenbosch University, 2017. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Alkali activated materials (AAMs), also referred to as geopolymer concretes, are a new generation of alternative construction materials, which are formed through the alkali activation of clinker-free binder materials, such as fly ash and slag. Compared to Ordinary Portland cement (OPC) concrete, the production of AAMs is associated with low energy consumption and low carbon dioxide (CO2) emissions, together with promising mechanical properties. The main goal of this study is to determine the structural use of a fly ash/slag based AAM, activated with sodium silicate and sodium hydroxide. The mechanical properties, with the focus on the compressive strength and the elastic modulus, as well as the structural behaviour of reinforced AAMs are investigated to achieve this goal. For the mechanical properties of AAMs, several of mix parameters were varied, which include: the type of activator; the calcium content; the activator concentration; the dosage; the modulus of the activator; and the coarse aggregate content and size. Compressive strengths of up to 67 MPa were obtained, while the elastic modulus was low in comparison with that typically found for OPC concrete, with values between 10 GPa and 32 GPa. The mechanical properties were mainly influenced by calcium content, sodium hydroxide concentration and the activator modulus. Large scale reinforced AAM beams were tested in bending in order to obtain the flexural behaviour of reinforced AAMs, while reinforcement pull-out tests were performed to determine the bond behaviour between AAMs and the reinforcement. For both these tests, two AAM mixes were compared against two OPC mixes with similar strengths. It was found that it is possible to use design codes, such as the EN 1992-1-1, (2004), for the ULS design of reinforced AAM beams. However, attention has to be given to the low elastic modulus in order to reduce the large deflections of the AAM beams. The design codes also seem to be inadequate for the deflection calculations of AAMs. Promising results were obtained in terms of the design bond stress of AAMs, as they were generally higher than that of the OPC-mixes. This indicates that shorter embedded lengths can possibly be used for AAMs. It can be concluded that the AAMs is still some time away from being used as a structural material, as there is still a number of issues, for example the low elastic modulus, that need to be addressed. However, there is potential for AAMs as a structural material, if these problems are solved. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Alkali geaktiveerde materiale (AGMe), ook genoem geopolimeerbeton, is ’n nuwe generasie van alternatiewe konstruksie materiale. AGMe bestaan uit klinker-vry binder materiale, soos vliegas en slagment, wat geaktiveer word deur alkaliese oplossings. In vergelyking met normale “OPC” beton, word AGMe verband gehou met lae energieverbruik en lae vrystelling van koolstofdioksied (CO2). Belowende meganiese eienskappe is ook al verky met AGMe. Die hoofdoel van hierdie studie is om die strukturele gebruik van ’n vliegas/slagmentgebaseerde AGM, geaktiveer deur natrium silikaat en natrium hidroksied, te bepaal. Dit was gedoen deur die meganiese eienskappe, met die fokus op die druksterkte en elastisiteitsmodulus, sowel as die stukturele gedrag van bewapende AGMe te ondersoek. Vir die meganiese eienskappe van AGMe, was verskeie meng variasies getoets . Hierdie meng variasies sluit in: die tipe aktiveerder; die kalsium inhoud; die aktiveerder konsentrasie; die aktiveerder- dosis en modulus; en die klip inhoud en grootte. Druksterktes van so hoog as 67 MPa was verkry, terwyl die elastisiteitsmodulus laag was (tussen 10 GPa en 32 GPa) in vergelyking met tipiese waardes verky deur OPC beton. Die meganiese eienskappe was hoofsaaklik beinvloed deur die kalsium inhoud, natrium hidroksied konsentrasie en die aktiveerder modulus. Groot skaal bewapende AGM balke was getoets in buiging om die buig gedrag van bewapende AGMe te bepaal, terwyl die bindings gedrag tussen AGMe en staal bewapening verkry was deur bewapening uittrek toetse. Twee AGM menge was vergelyk met twee OPC menge met dieselfde sterktes, vir buide hierdie twee toetse. Dit was gevind dat ontwerp kodes, soos die EN 1992-1- 1, (2004), kan gebruik word om bewapende AGM balke te ontwerp, maar aandag moet gegee word aan die lae elastiteitsmodulus om die groot defleksies te verhoed. Dit blyk ook of die ontwerp kodes onvoldoende is vir die defleksie berekeninge van AGMe. Belowende resultate was verkry in terme van die ontwerp-verbindingspanning vir AGMe, wat oor die algemeen groter was invergelyking met die OPC menge. Dit dui aan dat korter verbindings lengtes heel moontlik gebruik kan word vir AGMe. Daar kan tot ’n gevolgtrekking gekom word dat AGMe groot potensiaal het as ’n alternatiewe strukturele materiaal, maar verkeie probleme, soos die lae elastisiteitsmodulus, sal eers ondersoek en opgelos moet word. | af_ZA |
| dc.format.extent | 169 pages : illustrations | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/100809 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Geopolymers | en_ZA |
| dc.subject | Construction materials -- Mechanical properties | en_ZA |
| dc.subject | Alkali-aggregate reactions | en_ZA |
| dc.subject | Structural analysis (Engineering) | en_ZA |
| dc.subject | Fly ash | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | The structural use of alkali activated materials (Geopolymers) | en_ZA |
| dc.type | Thesis | en_ZA |