Macroscopic mechanical properties and microstructure characteristics of steel slag fine aggregate concrete

Several studies investigated the macroscopic mechanical properties of steel slag fine aggregate concrete. However, few studies have been conducted to evaluate the effect of steel slag fine aggregate (SSA) on the microstructural characteristics of concrete. This study mainly investigated the microstructure characteristics of the concrete and mortar mixtures incorporated with different SSA contents combined with macroscopic mechanical properties. The steel slag particles were grounded into smaller particle sizes ranging from 1 to 4.75 mm to obtain SSA and incorporated into cement-based composites to replace natural sand at 0%, 10%, 20%, and 30%. The X-ray fluorescence spectrometer (XRF), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), nanoindentation, and Mercury Intrusion Porosimetry (MIP) tests were carried out to investigate the microstructure characteristics of the cement composites . The results indicate that the 30% and 10% SSA content improved the compressive strength of mortar and concrete specimens by 1.13% and 5.60%, respectively. The SSA enhanced the hydration products of the cement matrix , which densified the matrix, reducing the number of micro-cracks. Moreover, the EDS's result indicates that the interface transition area of SSA is approximately 8 μm, higher than that of natural aggregate. The average hardness and elastic modulus are 24.0% and 67% higher than that of natural aggregate, respectively. Minimum porosity and desirable pore structures were achieved with 10% SSA content. The fractal dimensional analysis showed that the fractal dimension has a good correlation with macroscopic mechanical properties and pore structure parameters. • In this study, The highlights were summarized as follows: • Combine the macroscopic mechanical properties and microstructure characteristics of SSC for analysis. • The microscopic characteristics of SSC are studied from multiple perspectives through various microscopic methods. • The relationship between the fractal dimension of SSC and various pore structure parameters and basic strength is analyzed.