Research Of Enhance Mechanism And Application On Supersulphated Cement Using Metallurgical Slag

Super-sulphated cement, also known as Sulphate-activated slag cement or Gypsum-slag cement, it uses sulphate combined with appropriate alkaline to stimulate hydration. Super-sulphated cement has many advantages, such as excellent sulfate resistance, high strength, low hydration heat, high temperature resistance, low energy consumption.Through comprehensive performance research of different super-sulphate cement systems, this study identifies the suitable content range of different binders in each system, determines the optimized proportion which obtains good workability, mechanical properties and durability, and realizes a safe planned high-value use of metallurgical slag to save the land of stockpiling and protect natural resource.Two systems are studied in this paper. They are super-sulphated cement with GBFS and super-sulphated cement with steel slag; Comprehensive performance research includes water requirement for normal consistency, setting time, stability, compressive strength, flexural strength, drying shrinkage, carbonation test, freezing-thawing test, XRD, SEM and thermal analysis.The results show:(1)By adjusting the proportion,32.5,42.5 and 52.5 strength grade super-sulphated cement which meets the national standard can be prepared. (2)Alkaline activator is able to adjust setting time and water requirement for normal consistency of super-sulphated cement, improve the early strength. Clinker has stimulated effect to the hydration of steel slag and slag, appropriate dosage of clinker can significantly improve the strength of super-sulphated cement. (3)28d compressive strength of super-sulfated cement with GBFS and 1%clinker content is more than 60MPa. Changing the type of gypsum, the setting time of super-sulphated cement increased and mechanical strength decreased. Additives have good adaptability and no obvious influence on super-sulphated cement. (4)The finer the fineness of steel slag, the higher the hydration activity which causes the cement sets faster and gain higher strength. Fly ash extends the setting time of super-sulphate cement with steel slag, improve later strength. Calcined kaolin increases water requirement for normal consistency, extends the setting time and improves strength. (5)The anti-carbonation and anti-freeze performance of super-sulphated cement is poor. (6)The hydration products of super-sulphated cement are mainly ettringite and CSH gel. SEM observation found that there residues gypsum phase and (steel) slag particles which are not fully hydrated in hardened cement paste. There are more pore in hardened paste of super-sulfate cement with GBFS, ettringite crystal grows on the pore wall and its shape is short rod or fine needle; There are less pore in hardened paste of super-sulfate cement with steel slag, the fine needle ettringite crystals generates from the interface between the hydration products and (steel) slag particles.