Melting Concrete

name         Alex
status       other
grade        9-12
location     N/A

Question -   Does concrete melt?  If it does, at what temperature?
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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
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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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