This research analyzes the microstructure of hardened blended cement pastes. Fly ash was used to replace Portland cement type I paste. Test results indicated that hardened blended cement paste were significantly affected by duration after mixing. The X-ray diffraction (XRD) and the scanning electron microscope (SEM) showed changes of microstructure by duration.

This paper presents the results of an experimental study on the compressive strength, splitting tensile strength and modulus of elasticity characteristics of high performance concrete. These tests were carried out to evaluate the mechanical properties of HPC for up to 7 and 28 days. Mixtures were prepared with water to binder ratio of 0.40. Two mixtures were containing fly ash at 25%, silica fume at 5% cement replacement, respectively. Another mixture was contains blast furnace slag and fly ash at 25%. Three standard 100¥a200 cylinder specimens were prepared. HPC showed improvement in the compressive strength and splitting tensile strength when ordinary Portland cement was replaced with silica fume. Compare with specimens FA25 and BS25FA25, specimen SF5 showed much more modulus of elasticity. It shows that the use of the blast furnace slag of 25% and fly ash of 25% cement replacement has caused a small increase in compressive strength and splitting tensile strength and modulus of elasticity compared to the only use of fly ash of 25% at 28days. The results indicated that the use of blast furnace slag or silica fume provided the good performance compare to fly ash when the mechanical properties of the high performance concretes were taken into account.

The present study concerns a technique for determining the chloride binding capacity, using the XRD curve containing the peaks for Friedel's salt. The influence of chloride binding on the corrosion behaviour was also evaluated. The binding capacity of chloride ions in cement paste was determined by the water extraction method. As a result, it was found that the chloride binding capacity is strongly dependent on the W/C, binder type, curing age and total chloride concentration in the paste. It is notable that chloride binding has a crucial influence on corrosion propagation: an increase in the binding capacity resulted in a decrease in the corrosion rate at a given chloride concentration in mortar specimens. However, the impact of chloride binding on the onset of corrosion was marginal, presumably due to a release of bound chlorides into free chlorides at the stage of corrosion, accompanying a pH fall in the vicinity of the steel. A strong relation between the peak intensity for Friedel's salt and the concentration of bound chloride was observed, which can be used to determine the bound chlorides and thus the risk of chloride-induced corrosion of steel in concrete.

This paper reports an investigation in which the performance of fly ash, blast furnace slag and silica fume high strength concretes were studied under 7 and 28 curing days. Three high strength concrete mixtures were made in this investigation. Mixtures containing 25% fly ash, 25% fly ash and 25% blast furnace slag, and 5% silica fume as cement replacement, respectively. The water-binder ratio of all the high strength concrete mixtures was kept constant at 0.34. The replacement of silica fume in the high strength concrete mixtures indicated higher value of the compressive strength, splitting tensile and modulus of elasticity. In addition, blast furnace slag is effective for strength and modulus of elasticity improvement between 7 to 28 curing days.

The use of mineral admixture such as fly ash, blast furnace slag and silica fume in making high performance concrete has increased. The objective of this study is to investigate mechanical properties of compressive strength, splitting tensile strength and modulus of elasticity of hardened high performance concrete.