Influence of calcium sulphate to plasticiser/superplasticiser interaction on concrete performance
| dc.contributor.advisor | Combrinck, Riaan | en_ZA |
| dc.contributor.author | Bessinger, Johandre Marthinus Hubert | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. | en_ZA |
| dc.date.accessioned | 2020-10-20T16:23:18Z | |
| dc.date.accessioned | 2021-01-31T19:37:23Z | |
| dc.date.available | 2020-10-20T16:23:18Z | |
| dc.date.available | 2021-01-31T19:37:23Z | |
| dc.date.issued | 2020-12 | |
| dc.description | Thesis (MEng)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: With the continuously increasing use of concrete as a construction material the development of materials to enhance concrete performance has received a great deal of attention over the past few decades. However, one cause of inadequate concrete performance is found to stem from the cement production process itself. During the grinding of clinker, calcium sulphate dihydrate (gypsum) is added to produce cement. It is noted that the milling of clinker and calcium sulphate, to produce cement, causes peaks in temperature at localised areas within the mil. These increased temperatures result in the dehydration of calcium sulphate dihydrate to hemihydrate and to a lesser extent, anhydrite. Calcium sulphate regulates the hydration of tricalcium aluminates; the reaction of tricalcium aluminates with calcium sulphate dominates the early hydration stage of cement. This facilitates a dormant period during which cementitious materials, such as concrete, maintain its workability which allows sufficient time for transport, placement and finishing of concrete. This dehydration of dihydrate to hemihydrate, and to a lesser extent anhydrite, influences the solubility and dissolution rate of the calcium sulphate in cementitious materials. The type of calcium sulphate therefore influences the hydration kinetics of cement. This dehydration of dihydrate to hemihydrate particularly influences the setting time and susceptibility to false/flash set of cementitious materials. Modern concrete design often includes the use of chemical and mineral admixtures to provide improved fresh and hardened state properties that produce higher quality concrete structures. However, chemical admixtures such as plasticiser/superplasticiser, incorporated into concrete to increase workability or reduce water demand while maintaining workability, also have an affinity towards tricalcium aluminates in cement. This gives rise to cement – plasticiser/superplasticiser compatibility issues caused by the variation in type of calcium sulphate present in cement. This study therefore aims to establish the influence of the relation between calcium sulphate and plasticiser/superplasticiser on concrete performance. The influence of this interaction on concrete performance is evaluated through the use of slump,slump flow, rheology, setting time and compressive strength properties. An attempt is made to explain the influence of the relation between calcium sulphate and plasticiser/superplasticiser on the aforementioned concrete properties by considering the influence of plasticiser/superplastisers on calcium sulphate solubility. Solubility tests showed that the presence of plasticiser/superplasticiser increases the solubility of calcium sulphate hemihydrate and to a lesser extent, dihydrate. A correlation is found between the solubility of calcium sulphate and concrete fresh state properties. The presence of hemihydrate in cement is found to cause a decrease in concrete workability while increasing the rate at which concrete stiffens. The presence of hemihydrate also causes the rate of early compression strength gain to increase. This is verified by evaluating the influence of calcium sulphate – plasticiser/superplasticiser combinations on hydration temperature curves. From the evaluation of temperature hydration curves it is observed that the type of calcium sulphate present in cement influences the length of dormant period during hydration; hemihydrate causing a reduction of the dormant period. The magnitude of this reduction in length of dormant period is observed to be dependent on the presence and type of plasticiser/superplasticiser. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: iv Opsomming Met die toeneemende gebruik van beton as konstruksiemateriaal, het die ontwikkeling van materiale om betonprestasie te verbeter baie aandag geniet oor die afgelope paar dekades. Daar bly steeds oorsake van onvoldoende betonprestasie wat oorsprong vind in byvoorbeeld die sementproduksieproses. Tydens die maal van klinker word kalsiumsulfaatdihidraat (gips) bygevoeg om sement te produseer. Temperatuurpieke kom voor op gelokaliseerde gebiede binne die meul tydens die maal van klinker en kalsiumsulfaat. Hierdie verhoogde temperature lei tot die dehidrasie van kalsiumsulfaatdihidraat tot kalsiumsulfaathemihidraat en tot 'n mindere mate, kalsiumsulfaatanhidriet. Kalsiumsulfaat reguleer die hidrasie van trikalsiumaluminate in klinker. Dit is die reaksie van trikalsiumaluminate met kalsiumsulfaat wat die vroeë hidrasie periode van sement oorheers. Die reaksie gee aanleiding tot 'n dormante periode waartydens sementhoudende materiale, soos beton, genoegsame werkbaarheid behou wat die vervoer, plasing en afwerking van beton moontlik maak. Die dehidrasie van dihidraat tot hemihidraat, en tot 'n mindere mate anhidriet, beïnvloed die oplosbaarheid en diffusietempo van kalsiumsulfaat in sementhoudende materiale. Die tipe kalsiumsulfaat beïnvloed dus die hidrasie-kinetika van sement. Hierdie dehidrasie van dihidraat tot hemihydraat beïnvloed veral die settyd en moontlike vals/blits set van sementhoudende materiale. Moderne betonontwerp sluit dikwels die gebruik van chemiese en mineraal bymiddels in om verbeterde vars en geharde eienskappe te lewer wat betonstrukture van hoër gehalte lewer. Chemiese bymiddels soos plastiseerders/superplastiseerders, wat by beton gevoeg word om die vars toestand te manipuleer, het egter ook 'n affiniteit vir trikalsiumaluminate in sement. Dit gee aanleiding tot probleme met die verenigbaarheid van sement - plastiseerder/superplastiseerder wat veroorsaak word deur die variasie in tipe kalsiumsulfaat wat in sement voorkom. Die doel van hierdie studie is om die invloed van die verband tussen kalsiumsulfaat en plastiseerder/superplastiseerder op betonprestasie, vas te stel.Die invloed van hierdie interaksie op betongedrag word geëvalueer aan die hand van uitsakking, uitsakkingsvloei, reologie, settyd en druksterkte-eienskappe. Daar word gepoog om die invloed van die interaksie tussen kalsiumsulfaat en plastiseerder/superplastiseerder op die bogenoemde v beton-eienskappe te verklaar deur die invloed van plastiseerders/superplastiseerders op die oplosbaarheid van kalsiumsulfaat in ag te neem. Oplosbaarheidstoetse het getoon dat die teenwoordigheid van plastiseerder/superplastiseerder die oplosbaarheid van kalsiumsulfaathemihidraat en tot 'n mindere mate -dihidraat verhoog. ‘n Korrelasie is gevind tussen die oplosbaarheid van kalsiumsulfaat en die vars toestand eienskappe van beton. Daar is gevind dat die teenwoordigheid van hemihidraat in sement 'n afname in die werkbaarheid van beton veroorsaak, terwyl die tempo waarteen beton verstyf, verhoog word. Die teenwoordigheid van hemihidraat veroorsaak ook dat die tempo waarteen vroeë druksterkte toeneem, verhoog. Dit word bevestig deur die invloed van kalsiumsulfaat-plastiseerder/superplastiseerder kombinasies op hidrasie temperatuur te evalueer. Uit die evaluering van hidrasie temperatuurkurwes is daar gevind dat die tipe kalsiumsulfaat wat in sement teenwoordig is, die duurte van die dormante periode tydens hidrasie beïnvloed. Daar is gevind dat hemihidraat die dormante periode verkort,waar die grootte van hierdie verkorting afhanklik is van die teenwoordigheid en tipe plastiseerder/superplastiseerder. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.format.extent | 125 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/109152 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Calcium sulphate | en_ZA |
| dc.subject | Plasticizers | en_ZA |
| dc.subject | Rheology | en_ZA |
| dc.subject | Building materials | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.subject | Superplasticity | en_ZA |
| dc.subject | Concrete -- Deformations (Mechanics) | en_ZA |
| dc.title | Influence of calcium sulphate to plasticiser/superplasticiser interaction on concrete performance | en_ZA |
| dc.type | Thesis | en_ZA |