In this study, corrosion behavior of six different dual-phase (DP) steels with varying morphologies and martensite content has been examined in comparison to ferrite-pearlite steel in concrete. Intercritical annealing and intermediate quenching heat treatments have been applied to the reinforcing steel in order to obtain DP steels with different morphologies and content of martensite. Corrosion experiments were conducted in two stages. In the first stage, the corrosion potential of steels embedded in concrete was measured every day for a period of 30 days in accordance with ASTM C 876 standard. In the second stage, anodic and cathodic polarization values of these steels were obtained and then the corrosion currents were determined with the aid of cathodic polarization curves. It has been observed that both the amount of martensite and the morphology of the phase constituents have definite effect on the corrosion behavior of DP steel embedded in concrete. As a result of this study, it is found that corrosion rate of dual-phase steel has increased with increase amount of martensite.

h i g h l i g h t s We investigated the performance of the mortar with marble dust and glass fiber exposed to high temperature. This article applied the Taguchi method and ANOVA analysis. The compressive strength increased with increase of marble dust percentage. The most important parameter on the responses was found as temperature degree.

This paper investigated the usability of marble dust and glass fiber against the harmful effects of freeze-thaw (FT) cycles on cement mortars as experimentally and statistically. To this end, the cement mortar specimens containing marble dust (0%, 20%, 40% and 50% by volume) and glass fiber (0 kg/m 3 , 0.25 kg/m 3 , 0.50 kg/m 3 , 0.75 kg/m 3) were prepared. The compressive and flexural strengths of the specimens were determined after being exposed to FT cycles. In order to reduce the numbers of experiments, an L 16 (4 2 Â 2 1) Taguchi orthogonal array was adopted to the study. Amounts of glass fiber, percentages of marble dust and cycles of freeze-thaw, were changed to explore their effects on the compressive and flexural strengths of the mortar specimens. Statistically effects of the factors were also determined by using analysis of variance (ANOVA) method. Finally, experimental findings were compared with statistical results and a good agreement between them was achieved.

Table 1 Mechanical properties of rubberized concrete (28 days) Properites Concrete 5% 10% 15% 20% without rubber lLB KLB lLB KLB lLB KLB ILB KLB

SAEIOIO structural carbon steel, which has a low cost price and wide range of use in the construction industry, has been studied as dual phase (DP) steel subjected to appropriate heat treatment, and its mechanical properties have been investigated under various tempering conditions. Intercritical annealing heat treatment has been applied to the reinforcing steel in order to obtain DP steels with different martensite volume fraction. In addition, these DP steels have been tempered at 200, 300 and 400 'C for 45 min and then cooled to the room temperature. Mechanical properties such as tensile strength, yield strength, reduction in cross-sectional area, total elongation, resilience modulus and toughness have been examined. Furthermore, fractographic examination has been done with scanning electron microscope (SEM) as well as metallographic examination of the steels. As a result of this study, it is found that mechanical properties of DP steel have changed according to the hardness and ratio of martensite phase. In addition, tensile strength, yield strength and resilience modulus of the steels have been reduced. In contrast, the total elongation, reduction of the cross-sectional area and toughness have been increased.