| 摘要 |
Pre-foamed polystyrene globules not more than 24 hours old are mixed into concrete for pre-cast concrete mouldings. Steam at 2 - 3 atmospheres is injected into the concrete once it has been cast into a closed mould. - In the prefd. version the steam is injected from the bottom and in large mouldings also from the sides. An impervious sheet of a material pref. plastic is placed on top of the mould. - The function of the polystyrene is to exert an internal pressure resulting from its swelling after the steam injection. This yields better moulding surface and improves their mechanical properties.
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