SGI VARIA ' SWEDISH GEOTECHNICAL INSTITUTE STATENS GEOTEKNISKA INSTITUT

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STATENS GEOTEKNISKA INSTITUT

'

SWEDISH GEOTECHNICAL INSTITUTE

SGI VARIA

¹⁸⁵

Jan Hartlen, Pär Elander, Sten Kullberg.

Tom Lundgren, Bengt Rosen

RESTPRODUKT FRAN VAT-TORR RöKGASAVSVAVLING Laboratoriebestämning av egenskaperna hos ostabiliserad och stabiliserad produkt

Rapport till REFORSK 1986-12-22

LINKÖPING 1987

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portion of fly ash is approximately twice that of the desulphurization product (a 2:1 ratio). If cement is added, strength increases and per

meability decreases further. When adding cement, the proportion of de

sulphurization product should be reduced. The addition of 3-5% cement produces an exceptionally impervious product suitable, for example, in covering environmeQtally hazardous waste. Freeze-thaw tests have shown that mixes of fly ash and desulphurization products are not frost

resistant. However, a frost-resistant product appears obtainable ^by adding at least 10% cement together with sand or an air pore agent.

The products become brittle after hardening, leading to a risk of crack

ing. Tests have shown that a certain degreee of spontaneous healing may be obtained. Where usage involves high demands, special construction measures must be taken to reduce the risk of cracking.

As well as dust creation, environmental effects include leaching of salts and heavy metals. Leaching tests of different mixes have shown that it is primarily chlorides that are easily soluble.

In the hybrid products, the salt concentrations in the desulphurization product control the concentrations in the leached water. The heavy metal concentration from the desulphurization products are of the same order of size for most metals as for leachate from fly ash, even if varia- tions occur in both directions. Leachate from the hybrid products does not differ significantly in any way from the basic products. Therefore, stabilization with cement does not appear to lead to any general binding of metals, even if some influence has been found. If the hybrid products are permitted to harden for a longer period of time, initial tests indicate that the leaching properties may change favourably. Owing to the very

high impermeability of the hybrid products, leaching of heavy metals will be slight. However, environmental analyses, such as those described in Chapter 9, should normally be performed before the product is used.

The hybrid product appears suitable for covering environmentally hazardous waste, being fully comparable with clay sealing and sand-bentonite sealing as specified in the Mine Wastes project of the National Swedish Environment Protection Board.

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