Fineness of Densified Microsilica and Dispersion in Concrete Mixes. Volume 1 or 2

摘要

This study explores the effect of densification of microsilica on the mechanical and other engineering properties of concrete used on Ohio Department of Transportation (ODOT) projects. American Society for Testing and Materials (ASTM) C 1240 requires wet-sieved microsilica to pass a No. 325 sieve with no more than 10% retained. Densified microsilica samples submitted to ODOT sometimes do not meet this specification, since the sieving process may not be able to break the bonds formed due to densification. During this study, No. 325 sieve tests on three microsilica types (undensified, densified, and abused by prolonged exposure to moisture) were performed at the ODOT laboratory, but none of the materials tested were found to conform to the ASTM fineness specification. This calls into question the application of this procedure to assessing the suitability of densified microsilica for use in concrete. In contrast, the compressive and flexural strengths of concretes mixed with each of the three microsilica types exceeded those envisaged by ODOT Item 499.03 Concrete-General: Proportioning.