A new gelling material: properties of recycled aggregate concrete under conditions of complete cement replacement using steel slag, ore slag and fly ash

This study investigates the material properties of different types of Soil Solidification Rock (SSR) in comparison with Portland Cement (OPC), using techniques such as X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The strength and calcium-silicon ratio of the SSR paste was determined, and its overall quality was comprehensively evaluated. Under the condition of 9% SSR incorporation, recycled aggregate completely replaced natural aggregate, allowing for an in-depth analysis of the effects of different SSR types on the mechanical properties and sulfate resistance durability of recycled aggregate concrete (RAC). The results indicate that factors such as the water-binder ratio, calcium-silicon ratio, and the content of fly ash and steel slag significantly affect SSR performance. The optimal hydration reaction occurred with a water-cement ratio of 0.55. Additionally, when the calcium-silicon ratio was below 3, higher values correlated with increased 28-day strength of SSR mortar. Consequently, the calcium-silicon ratio can serve as a key index for evaluating SSR quality. Soil Solidification Rock Recycled Aggregate Concrete (SSR RAC) with approximately 30% fly ash content achieved an unconfined compressive strength (UCS) exceeding 15 MPa. However, fly ash and steel slag contents above 30% led to reduced compressive strength. For fly ash content of 30% or less, increasing fly ash content improved sulfate corrosion resistance in SSR RAC. Furthermore, the metal oxide content in the SSR RAC should be controlled within 20% to 30% for optimal performance.本研究以硅酸盐水泥（Portland Cement，OPC）为对照，采用X射线荧光光谱法（X-ray fluorescence spectroscopy，XRF）、X射线衍射法（X-ray diffraction，XRD）、扫描电子显微镜（Scanning Electron Microscopy，SEM）与能量色散光谱法（Energy Dispersive Spectroscopy，EDS）等表征手段，探究不同类型土壤固化岩（Soil Solidification Rock，SSR）的材料特性。研究测定了SSR浆体的强度与钙硅比，并对其综合品质进行了全面评价。在SSR掺量为9%、再生骨料完全取代天然骨料的工况下，本研究可深入分析不同类型SSR对再生骨料混凝土（recycled aggregate concrete，RAC）力学性能与抗硫酸盐侵蚀耐久性的影响。研究结果表明，水胶比、钙硅比以及粉煤灰与钢渣掺量等因素对SSR性能具有显著影响：当水灰比为0.55时，水化反应效果最佳。此外，当钙硅比低于3时，钙硅比越高，SSR砂浆的28天抗压强度越高，因此钙硅比可作为评价SSR品质的核心指标。粉煤灰掺量约为30%的土壤固化岩再生骨料混凝土（Soil Solidification Rock Recycled Aggregate Concrete，SSR RAC）的无侧限抗压强度（unconfined compressive strength，UCS）可超过15 MPa；但当粉煤灰与钢渣掺量超过30%时，抗压强度会出现下降。当粉煤灰掺量不超过30%时，提高粉煤灰掺量可提升SSR RAC的抗硫酸盐腐蚀性能。此外，为保证SSR RAC的最优性能，其金属氧化物含量应控制在20%~30%区间内。