| Research Abstract |
A siliceous powdered waste (primary component: SiO_2 density: about 2.65g/cm^3, specific surface area: 5〜200m^2/kg,) is discharged from a silica sand industry, classified as industrial waste (sludge) and chemically stable at normal temperature. About 0.6 million tons of siliceous waste per year as an industrial byproduct. The siliceous powdered waste is partially recycled, however about 80% remains unused. Finding an effective use for this material as a resource is an important issue.
In order to use siliceous powdered waste effectively in high-fluidity concrete, the authors studied the mixing of concrete with siliceous powdered waste and its effect on fresh and hardening properties of the concrete. As silica sand products are commonly manufactured using wet processes, hence siliceous powdered waste is discharged wet. To investigate the broad application of siliceous powdered waste in the as-discharged state, as a consideration of energy conservation, experiments were performed for specimens with different moisture contents and different grades.
The findings of this study can be summarized as follows:
・The siliceous powdered waste was found to enhance the resistance to segregation of concrete, and to be applicable for use in high-fluidity concrete. The water-cement ratio was 0.50, the slump flow for the unit water content of 175 kg/m^3 was about 70.0 cm, and the 28-day compressive strength was about 35 Mpa.
・It is possible to manufacture concrete with homogenous fresh and hardening properties using siliceous powdered waste by calculating the unit water content with consideration of the water adsorbed in the siliceous powdered waste.
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