Study On Steel Slag And Blast Furnace Slag-Based Cementing Material

Cementing material from industrial waste residues has better physical mechanicalproperties and excellent durability property. It belongs to green building materials with thecharacteristics of energy saving, utilizing industrial waste and environmental protectionand has become hotspot in cementing material research field in recent years. Steel slag andblast-furnace slag, two major industrial waste residues, have potential hydraulic property.They were restricted wide use in the cement field for their lower activity. In this paper, thelow alkalinity cementing material of eco-type was prepared from steel slag andblast-furnace slag (SSC) through the physical activation and chemical activation based onthe idea of synergistic effect.Based on grinding performance of steel slag and blast furnace slag, a compositegrinding aid KD was develop and then high activity powder of steel slag and blast furnaceslag was prepared. It was found that specific surface area and particle size were the mainfactors to the mechanical strength of the SSC. The steel slag powder of below1μm and theblast furnace slag powder below3μm contribute most for the mechanical strength. Theappropriate grinding time were confirmed to be50min and80min, the correspondingspecific surface areas were486.2m2/kg and436.9m2/kg. In such case, the particlecontents of steel slag powder of below1μm and the blast furnace slag powder below3μmwere57.15%and79.95%, respectively.The effects of different chemical activators on performance of the SSC wereinvestigated, and a special activator HQ was developed with the mass ratio: desulfurizedgypsum65%, clinker13%, calcium hydroxide4%, calcium formate13%, sodiumsilicate2%, early strength water reducer3%. The SSC was prepared and the materialproportioning was: steel slag40.45%, blast furnace slag40.45%, activator HQ19.1%.The product conforms to Grade42.5GB175-2007(Ordinary Portland cement, Chinanational standard). In addition, the water requirement for the standard consistence, settingtime, and soundness were also up to the standard. The synergistic effect of between steelslag and blast-furnace slag raw materials, different components in activator, differenthydration products, and between hydration products and unreacted raw materials were themain factors for the strength formation and development of cementing material.The grinding effect of composite grinding aids KD and triethanolamine(onecommercially available grinding aid)were studied using X-ray diffraction (XRD), FI-IR and scanning electron microscopy (SEM). The results showed that the former has a bettergrinding effect result from the synergistic effect of functional groups such as hydroxy andlamine groups. The activated mechanisms of activator HQ and the hydration reactionmechanisms of SSC were studied using SEM and X-ray diffraction. The hydrationproducts were mainly ettringite and gel-type materials like hydrated calcium silicate andhydrated aluminate calcium.Durability is an important index to evaluate the performance of cementing material.The durability properties of SSC were investigated, such as long-term strength, dryingshrinkage, impermeability, carbonization, frost resistance and sulfate erosion. It wasshowed that SSC had better performance than ordinary Portland cement, except forrelatively poor carbonization. Therefore, SSC has excellent durability and can replaceordinary Portland cement in the application of general civil engineering structures.