Ancient Roman Pozzolanic Concrete Brick Fabrication

60 mins Ages 10-14 Outdoor

A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.

Materials Needed

  • • Hydrated lime (Calcium hydroxide) (1/2 cup)
  • • Crushed terracotta flowerpot brick dust (1 cup)
  • • Builder’s sand (1 cup)
  • • Cut milk carton or small plastic casting mold (1 unit)
  • • Safety goggles, dust mask, and gloves (1 set)

Pro Tips

  • → Crush old terracotta flowerpot shards into fine red powder inside a heavy canvas bag with a hammer.
  • → Mix hydrated lime, terracotta dust, and sand in a 1:2:2 ratio with water to form mortar.
  • → Pack into an empty half-pint milk carton mold: the lime reacts with reactive silicates in the brick dust to cure into real stone.

Safety First

Wear dust mask and safety goggles when handling powdered lime; avoid direct skin contact with wet lime.

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Step-by-Step Instructions

1

Step 1

Pound terracotta pot shards inside a canvas bag with a hammer to produce 1 cup of fine red brick dust.

2

Step 2

Mix 1/2 cup hydrated lime, 1 cup brick dust, and 1 cup sand in a bucket while wearing safety goggles and mask.

3

Step 3

Add water gradually until a thick, workable paste forms, then pack tightly into a cut cardboard milk carton mold.

4

Step 4

Smooth the top, let set for 48 hours, peel away the carton, and inspect the rock-hard Roman masonry brick.

What they are learning

Pozzolanic reaction chemistry Hydraulic underwater concrete curing Ancient Roman structural civil engineering