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The paper presents a methodology fordamage evaluation of fiber-reinforced concrete (FRC) exposed to elevated temperatures of 400 oC to 800 oC. The residual compressive strength fraction of cylindrical FRC specimens with a water–cement ratio of 0.47 and total fiber volume fraction of 1.2% was evaluated for mixtures with variousproportions of steel and polypropylene fibers. The residual compressive strength fraction increased with the increase in the proportion of steel fiber at 400 oC. The residual strength fractions of mixtures with variousfiber proportions changedless with increasedexposure temperature. The effectiveness of visual inspection and ultrasonic nondestructive tests in assessing theeffects oftemperature exposure and the residual compressive strength fraction was evaluated. The experimental results indicate apotential application of the nondestructive tests on damage assessmentof FRC with variousmixture proportions. Anequation for estimating the residual compressive strength fraction based on ultrasonic pulse velocity was developed.

This study is conducted (1) to examine the influence of recycled aggregate on interfacial transition zone (ITZ), strength, chloride penetration, and carbonation of concrete, and (2) to propose a method for improving strength, chloride penetration, and carbonation resistances of concrete using recycled aggregates. Five types of recycled aggregate, and four levels of water-binder ratio are used in this study. The recycled aggregate concrete is evaluated according to compressive strength, tensile strength, chloride penetration depth, and carbonation depth. The characteristics of ITZs in recycled aggregate concrete are also measured and used to explain the influence of recycled aggregate on the mentioned properties. Additionally, the double-mixing method for improving strength, chloride penetration, and carbonation resistances of recycled aggregate concrete is evaluated in this study. DOI: 10.1061/(ASCE)0899-1561(2003)15:5(443) CE Database subject headings: Recycling; Concrete aggregates; Chlorides; Carbonation.

This paper deals with the macrocell and microcell corrosion of steel bars in cracked concrete exposed to a marine environment. For this, short-term accelerated laboratory and long-term exposure tests were carried out. Test items include electrochemical and physical evaluations of corrosion, chloride ion content in concrete, and oxygen permeability through concrete. Analyses by scanning electron microscopy and electron probe microanalyzer were also carried out to confirm the deposit in the healed cracks. For an unhealed crack, the portion of the steel bar located at the root of the crack acts as an anode and other portions as a cathode. Also, microcell corrosion at the cracked region is higher than the uncracked region. Macrocell corrosion process and the degree of macro and microcell corrosion are significantly influenced by the water/cement. In a natural marine environment, narrower cracks heal due to the deposition of ettringite, calcite, and brucite in the crack. This reduces the corrosion rate significantly at the cracked region. DOI: 10.1061/(ASCE)0899-1561(2003)15:5(460) CE Database subject headings: Chlorides; Concrete; Corrosion; Steel; Cracking; Coastal environment.