This practical involves students making up different samples of concrete, waiting until dry and then testing the strength of the samples using masses or a 'g' clamp.
Equipment required (per set):
Using varying combinations of sand, gravel, cement and water, students can make a selection of differing types of concrete mixtures. These mixtures can be poured into empty petri dishes if the strength is going to be tested using 'g' clamps or into the mould templates if masses will be used.
- four disposable cups
- 'g' clamp
- teaspoon or large spatula
- petri dishes or mould templates x 4
- masses (optional)
- Nichrome wire (optional)
Testing strength using concrete bars
The bar templates can be found HERE in our templates section. They will need to be printed on fairly stiff card, cut out and then held together using paper clips. The mould can then be filled with the wet concrete mixture and left to dry.
Once the concrete has set, the bar can be placed on two 100g slotted masses, ensuring the centre of the bar is slightly off of the work surface. Masses can then be added to the centre of the bar until it breaks.
Further reinforcement can be achieved by placing lengths of nichrome wire into the wet concrete mix and allowing it to dry. The wires help hold the concrete together and improve rigidity and strength.
Testing using 'g' clamps
Once the petri dishes have been filled and left to dry, a 'g' clamp can be applied to the centre of the sample and screwed until cracks appear in the concrete. Students can count the amount of turns it takes for the sample to crack and can then compare the other samples.
When storing cement, ensure it is kept in a cool dry place. Moisture may harden the dry powder over time if kept in a humid environment.
Yellow builder's sand is best for making concrete although other sand types such as white sand are available through builders merchants which students may want to experiment with.
Tables showing different concrete mixes can be found HERE in our info library section.