CHARACTERIZATION AND POZZOLANIC PROPERTIES OF SILICA FUME STORED IN AN OPEN POND

A wide range of properties (e.g., physical, chemical, mineralogical, microstructural, and pozzolanic) of silica fume are reported. This silica fume was derived from silicon metal production and stored in ponds under water for about a year. Its properties are compared to those of the silica fume from the daily production. The characteristics of the ponded silica fume are high SiO2 > 95%, LOI < 2.6%, and total trace element content of about 3000 ppm. It crystalline matter is composed of quartz, cristobalite, silicon metal, silicon carbide, and wood chips. This silica fume has undergone some degree of diagenetic process that yielded aggregation and degraded its pozzolanic reactivity as measured by the rate of consumption of Ca(OH)(2). In turn, the silica fume from the daily production is characterized by its high pozzolanic activity. Nevertheless, the compressive strength of these two types of silica fume is about the same. This is in accord with other findings illustrating that strength gain results from both the filler effect and the pozzolanic properties.