Civil Engineering Reference
In-Depth Information
Large quarries spoil the landscape even if they eventually become overgrown
and part of the landscape. They can also lead to altered groundwater conditions
and damage local ecosystems. To extract granite for use as crushed stone by the
'gloryhole' method involves drilling the mountain or rock from the top and
extracting stones by drilling a vertical tunnel which gets wider the deeper it
goes. This means less visual disturbance of the landscape.
Stone often contains radioactive elements such as thorium and radium, and a
quarry can increase the general level of radiation in a neighbourhood by emitting
radon gas. Generally the extraction of slate, limestone, marble and sandstone
have very little, if any chance, of causing radiation risks. Extracting volcanic or
alum slate requires caution, including the measurement of radiation levels before
removing stone for general use.
Environmental hazards of the industry include noise, vibration and dust -
quartz stone dust is the most harmful. The more work stone needs, the greater
the potential damage. By using undressed stone direct from the field these prob-
lems are avoided. If radioactive stone is avoided in construction there will be no
problem during the use of the building, and demolition waste will also be inert.
All building stone is recyclable, especially from bridges, steps and other forms
of pressed blocks. These second-hand products are usually valuable. Crushed
stone has a potential for recycling when concrete is re-used as aggregate for fur-
ther concrete production.
Production of building stone
Stone quarrying has always been based on a simple and labour-intensive tech-
nology which had difficulty in competing with growing industrialization. The
work was heavy and could cause physical damage to workers. Developing tech-
nology could make the work lighter and should make stone a more competitive
material. In many countries with low and medium industrialization stone can
cost as little as a quarter of the price of concrete. In highly industrialized coun-
tries there are signs of improved competition as part of an aesthetic and qualita-
tive drive. A significant factor which will strengthen the case for using local stone
is that in conventional concrete production the amount of energy comprises
25-70 per cent of the price of the product, and is likely to increase.
Stone from fields and beaches lie freely scattered in nature. Throughout time these
stones have been used and carefully stored. In Denmark as recently as the twentieth
century, the round beach stone was so highly valued that several parts of the coast
have been totally emptied! This round stone is particularly suitable for building in or
near water, especially for piers. But the possibilities are still relatively limited, as con-
crete has difficulty bonding to the smooth surface. For larger buildings these loose
stones have usually been cut into rectangular blocks for ease of handling.
