The Research On The Hydration Characteristics Of Air Cooling Slag

Energy saving and emission reduction in steel industry have become an urgenttopic. In order to recover the sensible heat in molten slag, dry granulation technologyhas become a direction for processing slag and resource utilization. Currently, theresearch on whether the dry granulated blast furnace slag can replace the traditionalwater quenching granulated blast furnace slag or not in order to achieve goodapplication in cement haven’t been reported. Therefore, the comparative study onhydration property of air cooling slag blended cement and water quenching slagblended cement were investigated in order to provide experimental and referencebasis for the application of dry granulated slag in cement.Firstly, different basicity factors, temperatures of slag discharge and coolingmethods were designed, and industrial limestone, fly ash and other materials wereused to simulate the preparation of slags in laboratory. Then, XRD, IR, TG-DTA andSEM were used to analyze the mineral composition, structure, microscopicmorphology and other characteristics of slags in order to study the effect of basicityfactors and formation condition on the characteristics of slags. The research indicatedthat the composition, structure and other features of slags had close relationship withbasicity factor, temperature of slag discharge and cooling method.Based on the study of slag characteristics, through testing the compressive strengthof slag-Portland blended cement pastes, the influence of slags under different formingconditions on the mechanical strength of blended cement were analyzed. At28days,the compressive strength of blended paste prepared by the air cooling slag which thebasicity factor, temperature of discharge and glass content were0.9,1450℃and11.07%respectively was the best, and equaled to the industrial slag blended cementpastes. XRD, TG-DSC and SEM were conducted on the composition andmicrostructure of air cooling slag blended cement pastes which presented bettercompressive strength at28days, and the comparative study on water cooling slagblended cement were carried out. The results showed that the hydration products ofair cooling slag blended cement and water quenching slag blended cement were thesame, but at28days, the air cooling slag blended cement presented higher hydrationdegree and more denser hydration production structures. And the influences of aircooling slag, water quenching slag and industrial slag at various fineness on thecompressive strength of slag blended cement pastes were studied, the results showedthat with the increase of specific surface area of slags, the compressive strength ofblended cement pastes had different degrees of growth. At the same time, through testing the hydration exothermic rate of slag blended cement, the effects of slag oncement hydration evolution were analyzed and discussed.At last, the air cooling slag and water quenching slag which the basicity andtemperature of discharge were0.9and1450℃respectively were chosen as studyobject, and0.1M NaOH solution were used as alkaline solution to simulate reactioncharacteristics of slag in cement hydration solution. pH of leaching liquid at variousreaction ages were tested, in addition, the concentration of active Ca, Si and Al inleaching liquid were determined by ICP, also, the microscopic morphology andelement of the reacted slag were analyzed by SEM/EDS, and then the dissolutionproperty of slags in alkaline solution were studied, which provided reference value forhydration mechanism of slag in cement concrete.