| The influence of the replacement ratio, fineness of superfine slag powder on the properties of cement paste at different ages was investigated by tests with XRD. The results showed that compared with the reference slurry, the diffraction peak intensity of the Ca(OH)2crystal drops sharply in the28-day hydrated cement sample blended with superfine slag powder, and that the consumed quantity of Ca(OH)2is in close relation with the age of hydrated cement sample and the replacement. ratio and fineness of the powder. The hydration rate of the cement paste with PI000superfine slag powder(measured specific area:1824m/kg) is so quick that the secondary hydration reaction can be completed basically just in3days. No significant change is found in Ca(OH)2diffraction peak intensity in the period of3～60days. The hydrated cement’s absorbability of Ca(OH)2is enhanced with the increasing slag fineness and slag powder’s specific area. However, the hydration processes of such clinkers as C2S and C3S are not shortened with the decreasing quantity of Ca(OH)2crystal, which shows new hydration products produced. Hydrogrosularite and tobermorite can be observed at the age of3d, gismondine can be observed at the age of7d, and Granular calcium silicon stone can be observed at the age of14d, and hydrogarnet can be observed at the age of28d. It is also tested that superfine slag powder can promote the early ettringite formation.In this paper the influence of superfine slag powder on hydration property and paste performance at different curing temperature is also investigated. The results showed that with the increase of curing temperature, pore porosity of cement hydration sample reduced, and at the same time the number of holes with large diameter increased. Therefore structure ordered degree increased, the local density also increasee but not even, led to strength increased at first, then decreased.High curing temperature in the early age improved cement hydration degree, especially to binding materials added by superfine slag powder. But early hydration reaction was so rapid that further hydration was hampered, which resulted in the content of superfine slag powder in the concrete be restricted to some extent.This paper deals with RPC produced by superfine slag powder and natural sands with a low water-binder ratio(0.2or so), which strength can achieve100MPa after28d standand curing. An analysis, based on the mercury intrusion porosimetry, is made of the relationship between strength and pore structure parameters. The results show that the strength can be improved in the range of30-45%, when the dosage of superfine slag powder varied from5%to15%; the linearity between compressive strength, water-binder ratio and the hole with a diametre larger than100nm are0.72and0.92respectively.Early strength increase of complex concrete mixed with fly ash and superfine slag powder is more apparent, and post strength increase significantly higher than the base concrete.Only mixed10%superfine slag powder can effectively reduce the concrete28d chloride permeability coefficient. When binding materials is350kg/m3, the permeability coefficient was reduced by2.5%, while binding materials470kg/m3in by21%.28d chloride permeability coefficient of composite concrete mixed with FA and P1000super slag powder was lower than concrete mixed with FA and P800super slag powder, for example, while the binding materials was430kg/m3, reduced by34%; on the contraty, when mixed with S95slag powder and P100or P800respectively, the opppsite result was obtained.28d chloride permeability coefficient of composite concrete mixed with S95and P800slag powder was lower than concrete mixed with S95and P1000slag powder by the range of40%to55%.The early cracking resistance of concrete with high-volume mineral admixture was investigated by the flat tests. The results showed that per unit cracking area, as well as the cracking area’s growth rate of the concrete sample is enlarged with the increasing content of binding material; Experiments also have suggested that the concrete’s caring and shaping method has a great deal of influence on the early cracking resistance property of concrete with high-volume mineral admixture.Carbonization test showed that, carbonation depth of concrete only mixed with50%slag powder was much smaller than concrete only mixed with50%fly ash. Carbonation depth of concrete only mixed with fly ash is2～5times of concrete only mixed with slag powder. By adding with fly ash and slag powder or fly ash and superfine slag powder concrete’s resistance of carbonate are all improved. And the concrete’s resistance of carbonate is enhanced with the increasing slag fineness. |
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