This thesis investigates the shear capacity of concrete T-beams prestressed with CFRP cables (CFCC) and contributes to the scarce research available for shear behavior of FRP prestressed concrete beams. Four beams are tested under distributed load, while twelve beams are tested under four point bending. Three different a/d ratios of 1.5, 2.5 and 3.5 are investigated. The results show that the shear capacity of the beams increases significantly when a/d is reduced below 2.5. The effect of FRP stirrups on the shear capacity of the beams is investigated and it is shown that the minimum required stirrups according to CSA-S6-10 are ineffective in deep beams with a/d = 1.5. The accuracy of current North American shear design formulas for FRP prestressed concrete beams subjected to four-point bending and distributed load is evaluated. The available strut and tie models are studied for determining the shear capacity of FRP prestressed deep beams.

The results of an experimental and theoretical investigation into the behaviour of reinforced concrete flat slab-column connections are presented. In the experimental programme 33 lightweight and 8 normal weight slabs were failed in punching shear. The specimens were simply supported and loaded vertically through central, monolithic column stubs. Three lightweight aggregates were used, and the concrete strength and section depth varied. It was found that slabs made with Lytag, Solite and limestone aggregates failed at similar loads, but slabs made with Leca aggregate concrete failed at approximately 70% of the former group (other variables being equal). In the theoretical investigation an analysis was developed to model the various stages of the slabs' behaviour under increasing load. The analysis enabled the critical pre-failure and punching loads to be calculated. Satisfactory agreement was established between the pre-failure values. The load at which failure occurred in the compression zone was computed using one of two methods designed to accommodate the differing characteristics of the concretes used. The methods depend on an idealisation of the behaviour of the shear crack which enables the compression zone stresses to be. established. Comparison of these stresses with a criterion of failure gives the concrete failure load. The ultimate punching load includes the enhancing effects, on the concrete failure load, of inplane stresses and dowel action. Good agreement between the theoretical, and. experimental punching values was established. The thesis includes a review of previous experimental and analytical work performed on normal and lightweight aggregate slabs. The existing empirical data is shown to be limited in several areas, especially for lightweight aggregate concrete tests. The application of existing formulae to the present experimental work does not provide a satisfactory agreement with the results. Three of the equations axe re-evaluated to pr6vide a closer fit with the present test results and for a wider based group of lightweight aggregate tests. The provisions of ACI 318-71 and CP. 110 : 1972 are also applied to the slabs of the present test series, and are shown to be conservative. Finally recommendations for future work are given.

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Extensive literature reviews are presented in this thesis with respect to the hydration of slag, especially on the mechanism of hydration. The range of work in the thesis includes: 1) compressive strength testing on slag cement pastes and slag pastes with other alkaline activators; the effect of curing temperatures and slag compositions were specially discussed. 2) Analysis of pore fluid from slag/NaOH pastes. 3) Porosity and pore structure analysis of slag cement pastes as a function of age. 4) Phase development in hydrating slag or slag cement pastes. 5) Microstructural and microchemical development of slag hydration products. Electron microscopy has shown that several chemically and microstructurally distinct zones quickly develop in a hydrating slag cement paste. Initially, a dense layer of gel-like hydration product forms around slag grains. The microstructure and chemistry of the gel are not constant, but evolve with time. Microstructural evolution is manifested by the crystallization of the previously formed gel hydrate, with the formation of a hydrotalcite-like phase. This crystallization is accompanied by distinctive chemical evolution, in which Ca, Si and some A1 migrate into the outer matrix; however, Mg appears to be virtually immobile. The evolution results in the creation of pores in the in-situ slag hydration zones, and at the same time, the marked densification of the outer matrix. Mass balance calculations are used to support the microstructural observations and to generalize on them, so the extent of the densification potential can be assessed. The ability to calculate the potential for densification, at least in principle, is regarded as an important step forward in the design for durability. A theory, based on the microstructural observations, is proposed to account for the differences between the calculated and observed porosities.

The microstructure and performance of calcium sulfoaluminate (CSA) cements are described. CSA cements contain C₄A<sub>3S, 4CaO.3Al₂O₃.SO₃,and are interground with gypsum/anhydrite. They have been used structurally in China for more than 20 years and elsewhere as special cements in non-structural applications. Their long-term behaviour of depends on ettringite, a relatively fragile substance, and a novel matrix former compared with Portland cement. The mineralogy, evolution of hydrate and microstructure of CSA cement pastes and concretes were studied to relate hydration products and microstructure with performances. Samples taken from in-service structures in China, ranging from several to 25 years old, were investigated. Drying methods for cement pastes affect experimental results, especially for ettringite-based materials and are reported. Calorimetry, X-ray diffraction, microprobe and porosimetry are used to investigate early (<24 hours) and late hydration processes in different curing regimes. A "shrinking sphere" model is proposed to explain hydration processes. At early stages, mineralogy differs between inner and outer products: the former contain mainly AFm and C-S-H while the latter contains mainly ettringite and gibbsite. At 25°C, these differences persist but inner products densify the paste. At 55°C, and at 85°C, substantial siliceous hydrogarnet, forms after ~3 d. It is a major inner product. This results in a volume decrease and coarsening of pores. Long-term exposure to higher temperatures ~85°C is harmful. The impact of water:cement ratios on hydration mechanisms is reported. Depths of carbonation of CSA cement concrete are reported: results show similar resistance Portland cement concrete. Pipe immersed in seawater for 16 years shows that CSA cement has excellent resistance to seawater attack. The steel in the pipe is uncorroded even though chloride ions have penetrated the cover. Long-term exposure to high temperatures, 85°C, of CSA cement should be avoided but under normal in-service conditions its long-term behaviour is satisfactory.

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