Test and Microstructural Analysis of a Steel Slag Cement-Based Material Using the Response Surface Method.

Area of Science:

• Materials Science
• Civil Engineering
• Geochemistry

Background:

• Steel slag cement-based gel slurry (SCGS) offers a sustainable alternative in construction materials.
• Optimizing SCGS properties is crucial for enhancing its mechanical performance and application potential.
• Understanding the influence of supplementary cementitious materials like silica fume and fly ash is key to SCGS development.

Purpose of the Study:

• To determine the optimal preparation parameters for steel slag cement-based gel slurry (SCGS).
• To investigate the effects of silica fume, fly ash, and curing temperature on SCGS strength.
• To analyze the hydration products and strength development mechanisms of optimized SCGS.

Main Methods:

• Response surface methodology (RSM) was employed to model and optimize SCGS preparation.
• Analysis of variance (ANOVA) and 3D surface models were used to assess variable effects.
• Scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterized hydration products and microstructure.

Main Results:

• Optimal parameters were identified, leading to predicted compressive strengths of 32.59 MPa (3 days) and 55.81 MPa (28 days).
• Actual strengths closely matched predictions (31.78 MPa at 3 days, 53.94 MPa at 28 days), confirming model accuracy.
• Silica fume's SiO2 hydration and fly ash/steel slag's physical filling effects influenced early strength.

Conclusions:

• The optimized SCGS demonstrated reliable and high compressive and flexural strengths.
• Early strength is attributed to silica fume hydration and inert material filling effects.
• Later strength development is linked to C3S hydration in steel slag and volcanic ash activity of fly ash.