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Chloride exposures represent some of the most aggressive conditions in which concrete structures are located., Approaches followed in most national standards in the provision of durability for these normally give guidance in terms of mixture limits (minimum cement content and strength grade and maximum w/c), concrete cover depth and in some cases, cement type. In addition to controlling these, there are other routes that can extend performance, which concentrate either on (i) extending time to corrosion ini- tiation, by minimising rates of chloride ingress (eg controlled permeability formwork, silane coating and waterproofing admixtures) or (iij limiting corrosion rates, once conditions are such that the process can occur (eg corrosion inhibitors and stainless steel). This paper assesses the chloride resistance performance (in terms of chloride diffusion rates, chloride content at cover depth and reinforcement corrosion rates) of both conventional (methods in national standards) and other means of achieving corrosion resistant concretes and establishes how the more novel routes may fit within the mixture limit chloride durability specification frameworks. The results from tests on site produced concrete and concrete in a coastal exposure are used to explore the specification route for one of the novel systems (CPF).

At the beginning of 2000, a research and development program was begun to design and produce SCC using ternary blended cements with further additions of ground granulated blast furnace slag (GGBFS), silica fume or limestone filler, leading to the production and use of SCC in construction by 2001. SCC from actual construction works were evaluated, in fresh and hardened state, aimed at determining their compressive strength and some durability associated parameters, such as air permeability, chloride penetrability and sorptivity. SCC showed at least similar durability-related performance as compared to conventional concrete with similar compressive strength, although the latter had equal or lower W/C and higher cement content. Moreover, the special properties of the self-compacting concrete in the fresh state may lead to a significant reduction of compaction defects, thus improving the overall durability of the structure. The applicability of Codes and standards that impose limits for the W/C on a prescriptive basis for durability come into question. These limits should consider the actual durability related properties of SCC that show better performance than conventional concrete for a given W/C or cement content. Performance-related Codes could be more appropriate if they take into account the actual behavior of this new concrete.

In terms of recycling of materials and effective uses of resources, the application of solid wastes to materials for concrete has been discussed. If the wastes are used for materials for concrete, the leaching behavior of ions from concrete as well as durability of concrete is a serious issue, especially as the behavior of heavy metal ions in concrete is concerned. Currently, however, there is no method for evaluating the leaching behavior of heavy metal ions that is appropriate for concrete structures. Since samples are crushed and ground in testing methods used commonly now, almost all of the contents of heavy metal ions are measured including the metal ions that may not be leached out of concrete because of hydration reaction with cement. We should evaluate leaching behavior of heavy metal ions not from a powder sample of concrete but from a massive body such as a concrete structure. In this study, testing methods for determining the leaching behavior of heavy metal ions from concrete structures are investigated and a method for prospecting long term leaching of heavy metal ions from concrete is discussed.

Reinforcing steel in concrete is normally protected against corrosion due to the high pH-value of the pore solution of the concrete. When a critical chloride concentration in the concrete is exceeded at the steel surface the passive layer is destroyed and corrosion of the steel starts. This critical chloride content for the corrosion of black steel is strongly dependent on the pH-value of the pore solution: the higher the concentration of OH--ions the higher the critical chloride content. For steel fibres, earlier investigations have shown, that they do not corrode in concrete even in presence of high chloride contents. Therefore it could be assumed, that the critical corrosion-inducing chloride content of steel fibres in concrete is distinctly higher than that of conventional reinforcing steel. To verify this assumption the corrosion-inducing chloride content of steel fibres has been investigated in artificial chloride-containing pore solutions at different pH-values. Five different types of steel fibres, one lashing (or tying) wire and one as reference reinforcing steel were investigated at 3 different pH-value ranges. The concentration of chloride within the pore solution was gradually increased in time steps of 12 h. The beginning of corrosion was determined by electrical current as well as potential measurements. Furthermore, additional investigations were carried out with intermediate products of the fibre production (steel wires with different diameters) to investigate whether the critical chloride content of the wires depends on the diameter of the fibres. The investigations show that steel fibres in artificial chloride-containing pore so- lutions have a significant increased resistance against chloride-inducing corrosion compared to conventional reinforcing steel for high pH-values. With decreasing diameter of wires the critical chloride content increases gradually.

Fracture mechanics parameters, mainly Fracture toughness K1c and Critical ef- fective crack extension (Aacc), may be used to monitor deterioration of concrete members subjected to sulfate attack, specially Delayed ettringite formation. Concrete beams containing cements with different contents of C3A, gypsum and granulated blast furnace slag were casted and submitted to Fu's accelerated curing method (1), to trigger delayed ettringite formation. Then all specimens were immersed in 23 +- 1 oC saturated lime water for a period of 3 and 6 months, measuring the changes experienced in both Fracture Toughness and Critical Effective Crack Extension, following the Bazant-RILEM recommended practice. Additional sets of beams were tested to monitor Longitudinal Resonance Frequency, Ultrasonic Pulse Velocity and Length Change. X-ray Diffraction and Scanning Electron Microsope studies were carried out to confirm the presence of Delayed Ettringite Formation. At the present paper a brief introduction of Fracture Mechanics applied to concrete is included and test results up to date are presented.