A study on the influence of crack widths and type of bars (plain and deformed) on corrosion of steel bars in cracked concrete is presented here. Microcell and macrocell corrosions of plain and deformed steel bars were investigated on 10 × 10 × 40 cm single crack specimens with crack widths of 0.1, 0.3, and 0.7 mm. Water-to-cement ratios were 0.3, 0.5, and 0.7. Electrochemical investigations were also conducted on 15 × 15 × 125 cm multicrack specimens with plain and deformed bars. For these specimens, water-to-cement ratios were 0.5 and 0.7 and crack widths were varied from 0.1 to 0.4 mm. After electrochemical investigations, chloride ions in concrete, corroded areas, weight losses, and pit diameters of the steel bars were investigated. The entire study was carried out in an artificially created chloride ion-induced corrosion environment. The study concludes that the relationship between crack widths and corrosion rate is observed at the very early age of exposure. Water-to-cement ratio and corrosion rate relationship is clearer than crack widths and corrosion rate relationship. Deformed bars are more prone to corrosion than plain bars.

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 signifi...

To address SDG12 (ensure sustainable consumption and production patterns), and to provide technical evidence for alternative concrete constituents to traditional natural river sand, stone fine aggregate (SFA), brick fine aggregate (BFA), ladle-refined furnace slag aggregate (LFS), recycled brick fine aggregate (RBFA), and washed waste fine aggregate (WWF), ready-mix concrete plants were investigated. Concrete and mortar specimens were made with different variables, such as replacement volume of natural sand with different alternative fine aggregates, water-to-cement ratio (W/C), and sand-to-aggregate volume ratio (s/a). The concrete and mortar specimens were tested for workability, compressive strength, tensile strength, and Young’s modulus (for concrete) at 7, 28, and 90 days. The experimental results show that the compressive strength of concrete increases when natural sand is replaced with BFA, SFA, and LFS. The optimum replacement amounts are 30%, 30%, and 20% for BFA, SFA, and LFS, respectively. For RBFA, the compressive strength of concrete is increased even at 100% replacement of natural sand by RBFA. For WWF, the compressive strength of concrete increases up to a replacement of 20%. Utilizing these alternative fine aggregates can be utilized to ensure a circular economy in construction industries and reduce the consumption of around 30% of natural river sand.