Chemistry KS3 & GCSE: Why is concrete so brittle?
Mark Miodownik tests the strength of a concrete beam by walking along it.
He discovers that the concrete is not able to tolerate the bending effect his weight is having on it.
Compression is seen in the top surface of the beam, and tension is seen in the bottom of the beam, which causes it to fracture.
An animation is used to explain that tiny pores in the concrete expand when stretched, causing cracks to appear and grow.
This clip is from Materials: How They Work.
Show this clip to a class before challenging them to design a concrete beam that would perform better under tension (changing the ratios of the mix for example).
Students can then make these and they can be tested under tension as a class competition.
These clips will be relevant for teaching Chemistry at KS3 and GCSE/KS4 in England, Wales and Northern Ireland and National 4/5 or Higher in Scotland. The topics discussed will support OCR, Edexcel, AQA, WJEC GCSE in GCSE in England and Wales, CCEA GCSE in Northern Ireland and SQA National 4/5 and Higher in Scotland.