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WHC-SD-W100-TI-003 Rev. 0<br />

Pulverized fly ash contains mostly silica and alumina, with very little<br />

calcium. The lack of calcium requires addition of lime or cement to activate<br />

this material. Fly ash can be added in ratios as high as 10:1 and still<br />

obtain a suitable final waste form.<br />

Gypsum cement<br />

Gypsum cement is composed of hydrated calcium sulfate. It has a lower<br />

compressive strength than portland cement. The elimination of calcium<br />

hydroxide gives this material a lower pH than OPC.<br />

Plaster of paris<br />

Plaster of paris is the most recognizable gypsum cement. This same material<br />

is also used in wallboard.<br />

Envirostone"'")<br />

This material is a proprietary mixture based on gypsum cement. The<br />

proprietary additives are claimed to make this mix more compatible with<br />

organic and acidic wastes.<br />

Modified cements<br />

Cement mixtures can be modified to enhance their ability to incorporate<br />

difficult wastes, and to increase their resistance to loss of soluble waste<br />

constituents through leaching.<br />

Physical absorbents<br />

Physical absorbents are used to incorporate non-hydraulic materials such as<br />

_liquid arganics _into the -waste matrix.<br />

Polymer impregnated cement<br />

Polymer impregnation is a method to decrease leachability be filling the<br />

interstitial pores with water-resistant polymer.<br />

Thermoplastic Polymers<br />

Thermoplastic polymers are a class of materials that melt at elevated<br />

temperatures. These matrices can be used to immobilize materials through<br />

micro- and macro- encapsulation.<br />

Bitumen ( asphalt)<br />

Bituminous polymers are familiar materials used in the construction of roads,<br />

and in the roofing industry. They are produced from crude oil, and can have<br />

varying physical properties.<br />

Straight run<br />

G-4

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