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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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