Expansion Cracks

August 23, 2003

Expansionbreak copy

Provided by: Kent Barnes
Summary authors & editors: Jim Foster; Kent Barnes

Why is this sidewalk buckled? All materials expand and contract with daily and seasonal temperature variations. Solid rock, or manmade substances such as concrete, or even steel, can generate huge internal forces when there isn't enough room to expand. The photo above was taken on a hot (near 100 F or 37.4 C) summer day (July 13, 2003) in Great Falls, Montana, and the concrete sidewalk rafted as a result of the high temperatures. However, even though expansion cracks are evident, they weren't sufficient to handle the pressures of the constrained concrete.

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