Efflorescence is the presence of insoluble salts upon the surface of concrete or masonry products. The aims of this project were to understand efflorescence and to evaluate metakaolin as an additive for efflorescence prevention. Computer modelling was used in order to simulate the effect of alkali upon relevant phases. Alkali was shown to depress the solubility of calcium hydroxide via the common ion effect, increase, in general, the solubility of calcium carbonate via the foreign ion effect and dramatically increase the solubility and rate of uptake of carbon dioxide into solution. The raindrop model is an attempt to simulate the processes leading to efflorescence. A raindrop falling onto a roof tile is assumed firstly to leach ions from the tile, secondly, to absorb atmospheric carbon dioxide and thirdly to precipitate calcium carbonate. The raindrop model calculates that the formation of efflorescence is primarily dependant upon leaching rather than drying effects. Sensitivity studies show that even when significant sulphate is leached, calcium carbonate remains the prevalent efflorescent phase. Metakaolin, a type of burnt clay pozzolan, had previously been cited as preventing efflorescence. However, this study showed that the performance of metakaolin is affected by the presence of micaceous and other impurity phases which are activated upon heating to metakaolinization temperatures, and readily release alkalis. This study found that the main products of metakaolin hydration in alkaline solutions are gehlenite hydrate and amorphous C-A-S-H gels. The latter was shown to absorb alkalis, particularly potassium, from solution. Results are presented of wet-dry and renewal of leachant leaching tests on two metakaolin blends and a neat OPC paste control. Wet-dry leaching, judged to be the most realistic leach test, produces leaching trends not noted in other leaching tests.

Insulating historic masonry buildings will improve thermal performance. However, heritage requirements often limit the addition of insulation to the interior surface. This can lead to colder and wetter walls. Freezing temperatures coupled with high moisture levels in the brick leave the walls susceptible to frost damage. Current retrofit designs attempt to control condensation of interior moisture. However, these designs do not consider exterior moisture sources, nor do they allow for interstitial moisture to be easily removed. This thesis presents an innovative, ventilated masonry retrofit that utilizes drainage and drying to address moisture accumulation issues. Computer simulations are used to assess and compare the hygrothermal performance of typical and ventilated masonry retrofits. The results show masonry moisture contents are reduced when ventilation drying is provided. Further, these simulations show it may be possible to increase thermal insulation levels in historic masonry buildings without damaging the very façade to be preserved.

In the last decade, Australian civil engineers have not paid enough attention to earthquake resistant design of structures. It was commonly believed that the earthquake risk was insignificant thus earthquake resistant design was not considered for most buildings. Earthquake resistant design of structures has become an important issue in Australia following the Newcastle earthquake in 1989. / Masonry is one of the most commonly used materials throughout Australia for the construction of low rise buildings. Even though the history of past earthquakes has shown that masonry buildings suffered the maximum damage and accounted for the maximum loss of life, they continue to be popular. It was evident from the Newcastle earthquake that most unreinforced masonry structures were seriously damaged. Therefore it is important to retrofit and strengthen existing masonry structures to resist the potential earthquake damages. / For the last twenty years, several seismic retrofitting techniques for masonry structures have been developed and practiced, but rarely validated with experiments and numerical modelling. Further more, the research has been carried out mainly in America and Japan where the risk of major earthquake is high. In Australia, although unreinforced masonry is one of the most popular types of construction, research into seismic retrofitting of masonry structures is rare. / The purpose of this research is to develop a new, cheaper and high strength seismic retrofitting technique for masonry structures. An innovative retrofitting technique is presented for improving the seismic resistance of unreinforced masonry walls using cable systems. In this thesis, the experimental results from four unreinforced masonry walls and eight unreinforced masonry walls retrofitted with cable systems are presented. Seven unreinforced masonry walls retrofitted with FRP were also conducted in this research for comparison purpose. All walls were tested under combined constant gravity load and incrementally increasing in-plane lateral displacement reversals. The results showed that both the strength and ductility of tested specimens were significantly enhanced with this new technique. Seismic retrofitting of unreinforced masonry walls with cables proved to be an effective and reliable strengthening alternative. / In this thesis, a basic mechanical model has been introduced first using the simple truss model. Then, two nonlinear finite element models based on this basic mechanical model have been developed to validate the experimental results. One model is developed for unreinforced masonry walls retrofitted by cable system and the other model is developed for unreinforced masonry walls retrofitted by FRP. All of the models have been found between the analytical and experimental results are reasonably good agreement. The model takes into account the material nonlinearities as well as damage due to progressive cracking. Behaviour of the masonry is modelled using the theory of plasticity and cracking is modelled using smear cracking approach. The model is generated using ABAQUS Finite Element program. The validity of the model is established by comparison with the experimental results. It is shown that both of the numerical models are capable of predicting not only the load carrying capacity, but also the failure mode and, ductility of the retrofitted masonry walls. / This thesis reviews the literature on all seismic retrofitting techniques and compares their advantages and disadvantages to identify the most effective and economic retrofitting method for unreinforced masonry buildings. It also presents the basic concepts of seismic retrofitting and summarizes the findings from recent experimental and analytical research activities on the seismic retrofitting of unreinforced masonry buildings and provides some retrofit strategies on the most common failure modes. It is expected that this thesis will provide some guidelines to assist Australian engineers to retrofit unreinforced masonry buildings. / Thesis (PhD)--University of South Australia, 2005.

Thesis (Ph.D.) -- McMaster University, 2003. / Includes bibliographical references (leaves 90-95). Also available via World Wide Web.

Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 2000? / Amendments pasted onto front end-cover. Bibliography: p. 221-240.

Thesis (Ph.D.)--University of Adelaide, School of Civil and Environmental Engineering, 2004. / "November 2004" Bibliography: p.167-179.

Thesis (M.S. in civil engineering)--Washington State University, May 2008. / Includes bibliographical references (p. 53-54).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 221-226.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Richard E. Klingner. Vita. Includes bibliographical references.

Thesis (Ph.D.)--McMaster University, 2005. / Advisor: R.G. Drysdale. Includes bibliographical references (p. 270-276). Also available online.