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This paper examines the influence of different aggregate size distributions on the fracture behaviour of high strength concrete. Three-point bend test was performed on 63 notched beams casted using three aggregate size distributions and two water to binder ratios. The total fracture energy, GF, and critical stress intensity factor, KIC, were used to determine the fracture characteristic of concrete. The results show that the values of GF decrease substantially with increasing coarseness of aggregate grain structure, λ. Values of KIC also decreased but demonstrated only limited dependence on λ. In contrast, reducing the total w/b ratio substantially increases the value of KIC but had no measurable effect on GF

Uncertainties associated with modelling of deteriorating bridges strongly affect management decisions, such as inspection, maintenance and repair actions. These uncertainties can be reduced by the effective use of health monitoring systems, through which information regarding in situ performance can be incorporated in the management of bridges. The objectives of this paper are twofold; first, an improved chloride induced deterioration model for concrete bridges is proposed that can quantify degradation in performance soon after chlorides are deposited on the bridge, rather than when initiation of corrosion at the reinforcement level takes place. As a result, the implications of introducing proactive health monitoring can be assessed using probabilistic durability criteria. Thus, the second objective of the paper is to present a methodology for performance updating of deteriorating concrete bridges fitted with a proactive health monitoring system. This methodology is illustrated via a simple example of a typical bridge element, such as a beam or a part of a slab. The results highlight the benefits from introducing 'smart' technology in managing bridges subject to deterioration, and quantify the reduction in uncertainties and their subsequent effect on predictions of future bridge performance. © 2004 Elsevier Ltd. All rights reserved

Chloride-induced corrosion of steel rebar embedded in concrete is one of the major concerns influencing the durability of reinforced concrete structures. It is widely recognized that the carbonation in concrete affects the chloride diffusivity and accelerates chloride-induced reinforcement corrosion. The service load related cracks also have a dominant influence on the reinforcement corrosion. This study aims to investigate the potential impact of concrete carbonation on the chloride penetration resistance, and the rate of corrosion, in RC structures subjected to service related cracks, which is not yet fully understood within the literature. The experimental programme involves casting concrete prisms (100 x 100 x 500 mm) with different water-cement ratios of 0.4, 0.5 and 0.6 and with four different crack width ranges (0, 0.05-0.15 mm, 0.15-0.25 mm and 0.25-0.35 mm), developed through flexural loading of prisms. These samples were exposed initially to accelerated carbon dioxide (CO2) environment and then exposed to the accelerated chloride environment. Carbonation depth, chloride penetration, and the degree of corrosion (using half-cell potential and linear polarization resistance) were experimentally measured. The results indicated that (i): The depth of carbonation increases with the increase in crack width and w/c ratio, (ii) chloride penetration depth and chloride concentration profile in concrete structures increases significantly due to the influence of carbonation and (iii) half-cell corrosion potential and linear polarization resistance increases significantly when carbonated concrete samples are exposed to the chloride environment relative to the uncarbonated concrete samples.

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