CONCRETE REPLACEMENT

Concrete replacement

Waste paper sludge as a cement replacement method

Waste paper sludge

Paper mill sludge is the main environmental and economic trouble for companies in the paper and board industry. The paper sludge is a byproduct of the re-pulping and de-inking of paper. The total amount of sludge from paper mills only in UK annually is exceeding 1 million tons on an annual basis. The main process of disposal and recycling for sludge are land spreading as a fertiliser that can be used in agriculture, combustion ,in CHP plants in a paper mill, production of paper sludge ash, or disposal to landfill. (Glowacki 1994)

In functional terms, waste paper sludge ash could be described as a free flowing sand /silt. After the burning of waste paper sludge at more or less 800 °C, the accompanying ash has responsive alumina and silica, in the form of metakaolin that could add be used as an ingredient in the production of cement.

Potential applications of waste paper sludge and waste paper sludge ash

Waste paper sludge

Some of the possible uses of waste paper sludge in construction products, which involves the replacement of cement, include usage in board products like substitute fuels for manufacturing cement, plasterboard, and brick manufacture. The major bounding element is the difficult to manage nature of physical properties of the material and its content, which has a high amount of moisture. Waste paper sludge can be treated to divide the fiber and fractions of mineral and to dry out the material by utilizing a technique, which was developed in Canada.

Application

The waste paper sludge has been the most widely investigated value-added alternatives for RPS (Recycled Paper Mill Sludge). The material's high moisture and inorganic levels are the reasons commonly cited as limitations for this application. High fiber - low inorganic portions can be isolated through physical separation, and moisture content can be reduced to below the 30% level so that sludge combustion is sustainable in commercial burners/boilers. Use as a fuel in the cement industry may be a viable alternative since heavy metals will be encapsulated in the slag. (Pickell and Wunderlich 1995)

Significance of Recycled Paper Mill Sludge

Information on the amount of industrial waste generated by the pulp and paper industry in a worldwide basis is limited. Several studies carried out in North America assessed the quantity and source of paper mill sludge in the late 1990's. They reported that 5.8 million dry tons of residues were generated by the entire industry in 1995. Data concerning the amount of residue from recycling operations is also limited. In 1998, the potential residue from all mills with de-inking capacity in North America was reported to be over 4.9 million tonla from an installed capacity of 9.7 million tonla. A survey of the Canadian pulp and paper industry reported solid wastes of 7.1 dry Mt, of which 12% or 825,000 t were from deinked paper solids. Similar statistics were computed for mills in Quebec where 45 mills reportedly produced 240,000 t/a of RPS (Recycled Paper Mill ...