Geoscience Reference
In-Depth Information
Introduction
1
PETROGRAPHY
cement, which can be mixed with sand and water to make
mortar for bonding masonry units. Gypsum is heated to
produce plaster and plasterboard. Large stone blocks are
used as armourstone protection for coastlines and
riverbanks. Aggregates from crushed rock are used for
roadstone, either loose or in layers bound by bitumen, as
macadam and asphalt. Both crushed rock and natural
gravel aggregates are mixed with Portland cement and
water to produce concrete. Aggregates of all origins are
used as fill materials for earthworks. Pure silica sands are
melted and cast into glass for windows and other
architectural elements. Clay soils can be used to make sun-
dried or kiln-fired bricks for masonry construction,
architectural terracotta, and ceramic tiles. Figure
1
provides
a summary of the main resources used for bulk
construction, showing the links between the various raw
materials, the finished products, and their uses.
Geomaterials are defined as 'processed or unprocessed
soils, rocks or minerals used in the construction of
buildings or structures, including man-made construction
materials manufactured from soils, rocks or minerals'
(Fookes, 1991). The definition deliberately includes man-
made materials such as bricks or cement but excludes
allied engineering materials whose manufacturing is more
extensive, such as steel and synthetic paints.
Geologically derived materials have been used in
construction for much of human history and, being
geologically common, are available worldwide. Strong
rocks provide dimension stone for masonry, cladding, and
flooring, while thinly bedded or cleavable rocks are suitable
for roofing. Limestone can be calcined to produce lime or
1
Cut or
crushed product
Kilned or
fired product
Raw materials
Mixture
Use
Slate
Sea and river
defences
Armourstone
Sandstone
+ bitumen
= asphalt
Surfacing
Igneous
rock
Crushed rock
Lime binders
Foundation fill
Limestone
Dimension stone
Gypsum plaster
Gypsum
Buildings
Mortar, render,
screed
Clay or
shale
Brick clay
Portland cement
Structures
Bricks and clay
products
Sand
Glass
Concrete
products
Concrete
Gravel
1
Flow chart showing the relationships between the main geological construction materials and their uses
(adapted from Woodcock, 1994).
