Structural demolition technologies

There are a number of criteria to consider when selecting the right demolition

procedure:

— Technical criteria: component materials, geometry and accessibility

— Radiation protection criteria: minimising aerosol release, primary and secondary waste, avoiding spreading decontamination, ease of decontamination, high level of recyclability of installations used

— Financial criteria: setup costs, equipment costs, operating costs, cutting services

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Fig. 4.26 Making a cut-out in the control area using wire saws and overlapping core drillings

— Strategic criteria: site location, demolition strategy, disposal routes, constraints of materials handling strategy

Demolishing concrete and reinforced concrete structures is often done using wire saws. These have the advantage that large-format blocks can be obtained which can be readily carried away; the drawbacks are that cutting and cooling water may be required and drill holes have to be made to guide the wires in first (Figure 4.26).

Contaminated concrete layers can be demolished as shown below, depending on the nature and depth of the contamination involved (Table 4.2, Figure 4.27).

Table 4.2 Methods for decontaminating reinforced concrete sections

Nature and Depth of Contamination

Method

Loose contamination on surface of concrete which can be wiped off

Vacuum, brush off, wipe off, wash or spray, apply chemicals

Subsurface contamination (has penetrated and attached itself)

Grind off, mill over large areas (Figure 4.27) flame hammer and chisel

Deeper contamination into concrete

Chisel off conventionally, mill over large areas, combine milling and chiselling

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Fig. 4.27 HOCHTIEF Decon surface milling system in use [36]