procedure

• Start with a mix of 1 vol. cement + 6 vol. soil + 6 vol. sand.
• Apply a layer of 1cm mortar on a block soaked in water and let it dray in shade.
• Observe the mortar for cracks.

interpretation

• If cracks appear, reduce the soil and increase the sand proportion.
  1 Cement + 5 Soil + 7 Sand.
• If mortar is too crumbly, increase the soil and reduce the sand proportion.
  1 Cement + 7 Soil + 5 Sand