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Melting Concrete
Name: Alex
Status: Other
Grade: 9-12
Location: N/A
Country: N/A
Date: July 2006
Question:
Does concrete melt? If it does, at what temperature?
Replies:
Alex,
Concrete does not melt, at least not in the way you may be
thinking. Concrete is composed largely of gravel an sand,
with Portland cement that holds the sand and gravel together
into a solid mass. The sand and gravel will melt, but you
will not be doing it in your kitchen oven! A temperature of
several thousand degrees is needed, and the result will be
much the same as the lava that comes out of volcanos. After
all, gravel and sand are just rock, as is molten lava. The
Portland cement in concrete, is a mixture of various hydrates
and silicates of calcium, aluminum and other elements. It too
is a "rocky" material that will not melt at any practical
temperature, either.
Regards,
Robert Wilson
Concrete is a very complicated mixture of different metal oxides,
hydroxides, and silicates (many of which form extensive,
interpenetrating networks), mixed with a filler material such as
gravel or rock. It does not maintain its chemical identity when
heated. If concrete is heated to a high enough temperature, the
hydroxides decompose to form oxides and water; the water is quickly
lost as the vapor. The remaining metal oxides are quite refractory;
they remain solid at very high temperatures. The rock components of
concrete will decompose or melt at differing temperatures depending
on their mineral composition.
So the short answer to your question is that concrete will decompose
rather then melt when heated, and the clinker that remains after it
cools back down will unmistakably not be concrete.
Richard Barrans
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Update: June 2012
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