Limits of Microfines Content in Manufactured Sand for Purposes of High Strength Concrete

摘要

Microfines with particle size being less than 75 μm are inevitably existed in manufactured sand (MS). According to GB/T 14684-2001 of the Chinese National Standard of Sand for Building, microfine content in MS used in concrete graded higher than C60 is limited to the level of 3%. The paper presents the results of studies on the C60 high strength concretes (HSCs) prepared from MS with microfine content of 3.5%, 7.0%, 10.5% and 14.0%. In addition to the workability and strength of the C60 HSCs, modulus of elasticity, drying shrinkage, chloride diffusion coefficient as well as freezing and thawing resistance were determined. Moreover, substitution cement with the microfine as mineral admixture is studied. Hereby, it was put forward that the microfine content in MS can be increased up to 10.5% when using MS to prepare C60 HSCs, and the part microfine can be used as mineral admixture, the substitution amount is approximately 10% of cement.