Mechanical properties, durability, and ITZ characteristics of full-grade dam concrete prepared by aggregates with surface rust stains

Abstract

Aggregates with surface rust stains (ASRS) is very common in the construction of water conservancy and hydropower projects. The purpose of this paper is to provide the possibility to utilize rusted raw rocks as aggregate in dam concrete. The physical and chemical properties of rusted raw rocks are measured. In addition, comparisons of their mechanics and the durability of dam concrete prepared by ASRS and rust-free limestone aggregates (RFLA) are investigated. The characteristics of interfacial transition zone (ITZ) between aggregate and paste are investigated by the means of scanning electron microscope with energy dispersive spectrum (SEM-EDS) and nano-indentation technology. The results show the apparent density and uniaxial compressive strength of ASRS are lower than the RFLA by 10 kg/m3 and 5.3 MPa, respectively. The compressive strengths of ASRS concrete are approximate those of RFLA concrete. The tensile strength of ASRS concrete is lower than that of RFLA concrete by 13 %. The ASRS slightly reduces the dam concrete frost resistance and impermeability. The ITZ average thickness of the ASRS sample is thicker than that of the RFLA sample by 15.0–20.0 μm. The values of indentation modulus and hardness observed across the ITZ in the ASRS sample are lower than those of the RFLA sample by 6.31 GPa and 0.11 GPa, respectively. The ASRS can be utilized as aggregates in dam concrete, such as in the structure with lower tensile strength requirements.