Freeze-thaw damage of ultra fine dredged sand concrete based on microstructure characteristics

Abstract

This study investigates the freeze-thaw damage of dredged sand concrete by conducting freeze-thaw cycles tests on concrete samples with different replacements of dredged sand. CT scanning tests, MIP tests, SEM tests, and XRD tests were performed. The test results indicate that the addition of dredged sand can optimize the micro pore structure of concrete and enhance the strength and frost resistance of concrete. The test results show that the freeze-thaw deterioration exhibits layer characteristics. The porosity is reduced by 22.49 % and 33.97 % when the dredged sand replacement is 25 % and 50 %, respectively. The total pore length of the concrete specimens M0, M25 and M50 are measured as 344.10 mm, 305.74 mm, and 286.37 mm, respectively. The connectivity decreases with the increasing of dredged sand replacement. The pore structure fractal dimension increases with the increasing of the dredged sand replacements. As the optimized pore structure is achieved by substituting some dredged sand, the frost resistance of concrete is improved. Finally, The relation between the porosity and the freeze-thaw cycles is established as well as the relation between freeze-thaw damage and compressive strength. Consequently, both the freeze-thaw life and compressive strength can be predicted based on the porosity.

Keywords

• Dredged sand concrete
• Microstructure
• Damage model
• Freeze-thaw cycles