Concrete with a pore solution of pH 10-12 is less alkaline than sound concrete but would still produce a strong color hange with phenolphthalein indicator. It therefore follows that the indicator test is likely to underestimate the depth to which carbonation has occurred. The indicator has not changed color near the top and bottom surfaces, suggesting that these near-surface regions are carbonated to a depth of at least 3 mm from the top surface and 5 mm from the lower surface. Where the indicator has turned purple - the center of the slab - the pH of the concrete pore fluid remains high (above 8.6, probably nearer 10).. Based on the above technical background, this study was devoted to examine the depth analysis of carbonated concrete quantitatively.

Many researchers have defined critical chloride content as a specific value. The studies reporting critical threshold chloride content have involved the experimental measurement of the average amount of the total chloride content. The studies have tried to define the critical chloride content within the scope of their experimental concrete mix proportion at arbitrary time. However, there is no agreement on its value. The purpose of this study is to explore the combined effect of oxygen and chloride on reinforcement corrosion. In the experimental recipe, water soluble oxygen is taken into account to define the critical chloride content. Corrosion current density of reinforcement was measured by linear polarization resistance method.

There is an increasing need for new materials and methods for rapid but durable repair of concrete. The author outlines the main properties and reports on some aspects of durability derived from laboratory investigation. Micro-fibre reinforced polymer cementitious materials provide early strength materials and can be considered dimensionally stable. Compressive and bonding strengths show a satisfactory strength. Meanwhile, the micro-fibre reinforced polymer cementitious materials had a low permeability which doesn’t allow water vapour to diffuse through the matrix. Details are expected to be given of successful applications on most of all concrete structures.