Page 12 - Haddonstone

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2.4 At a Glance Guide to Manufacturing Method Properties

Property Semi-dry Wet cast Fibre reinforced

Cube strength Typical range 35-50 MPa Typical range 35-50 MPa Typical range 35-50 MPa but with
enhanced tensile and bending
strength

Size More common to traditional Also suitable for large and Suitable for thin wall units and for
traditional units where increased
units such as cills, heads, structural units tensile strength is required

string courses, cornices etc.

Colour Highly authentic stone shades Highly authentic stone shades Highly authentic stone shades

Handling As natural stone As concrete As concrete

Appearance Slightly open texture, similar to Dense close texture with option Dense close texture with option of
as supplied natural Portland and Bathstones of secondary finishes. secondary finishes.

Appearance on Weathers in a similar manner to Retains supplied appearance Retains supplied appearance
Weathering natural Portland and Bathstones for a longer period for a longer period

Product Strength Function of unit geometry. Structural units can be both semi dry or Function of unit geometry. Thin wall

wet cast. For structural requirements reference should be made to units can be produced due to the

BS EN 1992 and BS EN 1996 the increased tensile and bending

strength. For structural requirements

reference should be made to BS EN

1992 and BS EN 1996

Product Output Highly cost effective through Requires greater mould Requires greater mould
multiple use of same mould investment or longer lead times investment or longer lead times

2.5 Summary of Main Finishing Methods for Cast Stone

Finishing methods Description

Rubbed Finish Dry rubbing is usually carried out with an abrasive pad or sandpaper block to remove surface laitance.

(Wet Cast only) Wet rubbing produces a clean smooth surface and can be of some help in delaying evaporation during the early

curing period.

Simulated Tooled Finishes Highly detailed designs can be achieved by taking mould plates from natural stone masters. Semi dry units also
allow a limited amount of post production reworking using traditional tools.

Acid Etching A good simulation of rubbed limestone can be achieved by the use of a solution of hydrochloric or another
suitable acid applied carefully to a previous well-wetted surface. A further improvement is possible by wet
rubbing down with an abrasive pad following the acid treatment.

Sand and Grit Blasting This is a popular method of removing surface laitance and exposing to a controlled degree the underlying
aggregate/cement matrix.

Wet Ground Finishes This is a method of finishing by which the surface of the units is removed to depth varying, according to

(Wet Cast only) requirements, from a nominal 1mm to a maximum not usually exceeding 3mm. In the same way as for natural

granite or marble, cast stone can be given a full polish, subject to the mix ingredients.

Extract from research report produced by the Concrete Technology Dept at Dundee University