Metallurgical slag as a component in blended cement

Abstract

Metallurgical slags (granulated and air-cooled), are disposed as waste from the ferro-manganese and ferro-manganese–silicon alloys manufacturing plants. They find little use unlike blast furnace slags from steel plants. Investigations were carried out to explore the possibility of using high MnO and low MnO metallurgical slags on samples obtained from an alloy plant in India. Low MnO granulated slag was used in making blended slag cement with ordinary Portland cement (OPC). Addition of slag lowered the compressive strength of the blended cement as compared to that of OPC used. However, the composition of a 50:50 blend, ground to 3000 cm 2/g (Blaine), was found to conform to IS 455:1989 for Portland slag cements and also to IS 269:1989, 33 grade OPC, with respect to standard consistency, setting times, soundness and compressive strength (22 MPa at 7 days and 33 MPa at 28 days) tests carried out as per IS 4031:1988. X-Ray diffraction analysis showed that low MnO granulated slag was non-crystalline, whereas the air-cooled slags were crystalline containing mainly quartz, MnO and Mn 2O 3. Chemical analysis showed that the slag samples were low in CaO and Fe 2O 3 contents and high in SiO 2, Al 2O 3, MnO, MgO, Na 2O and K 2O, thus indicating pozzolanic reactions contributing to a great extent in the strength development of blended slag cement compositions studied. High MnO (>15%) and MgO (>8%) containing slags were considered unsuitable for blended cements because of their deleterious effects. Air-cooled lumpy slag was evaluated for use as aggregates in concrete. All the tests were carried out as per IS 2386:1963, methods of test for aggregate for concrete and to conform to IS 383:1990, coarse and fine aggregates from natural resources. The material passed all the tests viz. crushing strength, impact value, abrasion, alkali aggregate soundness, except for deleterious materials content. This slag could be used, with slight modification, for non-structural concrete. The results of the investigations provide a direction for profitable plans for making blended slag cements.