Abstract
This article investigates the effect of carbon steel slag (CS) and stainless steel slag (SS) on the hydration of cement (OPC). Two slags were used to replace cement at a replacement ratio of 15% (CS15 and SS15) and 30% (CS30 and SS30), respectively, by binder weight. Test results demonstrated that the hydration rate of OPC-CS binder is similar to that of OPC-SS binder at 3 days but higher than the latter at later ages. The negative effect of steel slag (CS) on the strength of cement mortar can be neglected when its replacement ratio does not exceed 15%. X-ray diffraction (XRD) and thermogravimetry (TG) show that the incorporation of SS tends to decrease calcium hydroxide (CH) content more than the incorporation of CS in the cement matrix. BSE (backscattered electron)/EDX (energy-dispersive X-ray spectroscopy) analyses estimate the average Si/Ca ratio of CS30 and SS30 at 90 days to be 0.41(Ca/Si = 2.44) and 0.45(Ca/Si = 2.22), respectively, compared to 0.43 (Ca/Si = 2.33) for pure cement.
Highlights
As a key ingredient of concrete, cement with its huge production flows causes significant societal and environmental impacts
It is believed that the major active minerals of steel slags as well as cement are clinker minerals represented in calcium silicates [4, 5]
The e ect of steel slag (SS) compared to carbon steel slag (CS) is more obvious for declining hydration heat at the acceleratory period of the exothermic reaction
Summary
As a key ingredient of concrete, cement with its huge production flows causes significant societal and environmental impacts. Liu and Li [11] found that increasing steel slag fineness enhanced its early exothermic rate and increased early hydration heat and nonevaporable water content They observed that blended cement mortar containing finer steel slag gains higher 28-day strength. Several studies report about the valorization of the hydraulic properties of carbon steel slag or stainless steel slag one at a time, the di erence in the behavior between the two materials as a binder compared to each other is still unexplored. This study is aimed at investigating the in uence of carbon steel slag and stainless steel slag with high neness on the microstructure and the mechanical properties of cement Such investigations shall be bene cial for increasing the utilization ratio of these two by-products. Polished slag samples hydrated at 90 d were scanned with secondary electron (SE) in the electron microscope (FEI quanta 3D FEG, USA) with a complementation of EDX elemental mapping and backscattered electron (BSE) with applied electron energy of 15 kV
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