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Photocopy of typescript. / Bibliography: leaves 131-134. / viii, 134 leaves ill

Geopolymers, a class of largely X-ray amorphous aluminosilicate binder materials, have been studied extensively over the past several decades, but largely from an empirical standpoint. The primary aim of this investigation has been to apply a more science-based approach to the study of geopolymers, including introducing a variety of mathematical modelling techniques to the field. The nanostructure of geopolymers is analysed via an extensive literature review, and conclusions regarding the presence and role of crystallinity within the geopolymer structure are drawn. Si/Al ordering within the tetrahedral aluminosilicate gel framework is described by a statistical thermodynamic model, which provides an accurate representation of the distribution of Si and Al sites within the framework as well as physically reasonable values for the energy penalty associated with ordering violation. Framework and extraframework structure within the geopolymer binder are also described by the pair distribution function (PDF) technique, whereby synchrotron X-ray scattering data are converted via a Fourier transform-based method into real-space structural data on an Ångstrom length scale. Real-space Rietveld analysis of geopolymers crystallised at high temperature is used to back-calculate and analyse the original geopolymer structure, and the primary change in very short-range structure from the as-synthesised geopolymer to the high-temperature crystalline product is observed to be a shift in the location of the extraframework charge-balancing cation.

Geopolymer cements offer an alternative to, and potential replacement for, ordinary Portland cement (OPC). Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. There is already a considerable amount of work and research conducted on geopolymers in the past decades, and it is now possible to implement this technology commercially. However, to ensure that geopolymer becomes commercially available and able to be used in the world, further understanding of its ability to provide durable and long lasting materials is required. One main property which is still relatively unexplored compared to other properties is its shrinkage properties. The objective of this thesis is therefore to examine the shrinkage of geopolymers and factors which might influence it. / The factors which influence geopolymer strength were investigated as being the factors which may influence shrinkage. The selection of the activating solution is an important factor in forming the final product of a geopolymer. Activating solution SiO2/Na2O ratio is determined to be an important influence on the shrinkage of geopolymer. SEM images of the samples enable observation of the sample topology and microstructure. An important observation was the existence of a ‘knee point’ which also occurs in OPC shrinkage. The ‘knee point’ is the point where the shrinkage goes from rapid shrinkage to slow shrinkage. From SEMs it is noted that the samples past the knee point are shown to have a smoother topology which means it is more reacted. / Autogenous shrinkage is an important issue for OPC containing a high amount of silica, and is also a key factor in geopolymer shrinkage. Autogenous shrinkage is tested by keeping samples in a sealed environment where water lost to drying is kept to a minimum. It is noted that sealing and bagging the samples reduces the shrinkage considerably. The water to cement ratio, which is an important factor in OPC shrinkage, is also explored for the case of geopolymers. Water content plays an important role in determining early stage shrinkage, and has little to no effect on the later stage shrinkage. The water loss from the samples during drying on exposure to environment is noted and compared. The addition of more water did not necessary means that more water was lost. / Addition of slag is known to be beneficial to geopolymers by giving early structural strength and faster setting time. Commercial geopolymer concrete will also include the use of slag. However, the addition of slag up to a certain extent gives a deleterious affect on shrinkage. / A different type of Class F fly ash source with different composition data was used to see its effect on shrinkage, with only a slight influence observed between the two ashes tested. Fly ash was also ground for different lengths of time before use in geopolymerization, with grinding for less than 12 hours giving higher shrinkage than an unground sample, but shrinkage the decreasing with grinding for 18 or 24 hours. This initial higher shrinkage has been attributed to the mechanism of grinding which resulted in unevenly shaped fly ash particles taking up a larger initial volume resulting in higher shrinkage. The sample grinded for 24 hours showed higher shrinkage due to the particle size to be so fine that agglomerates may have form during mixing which would result in a lower reaction rate which increases the shrinkage. Elevated curing temperatures also reduce geopolymer shrinkage. / Thus, it is clear that the shrinkage of geopolymers is influenced by a wide range of variables, and more notably by a few important variables: activating solution ratio, addition of water, grinding and bagging. The shrinkage of geopolymers can be correlated to the strength to a certain extent. However, the understanding of the shrinkage of geopolymers is still at a very initial phase, and further research is required.