3
Natural : metal, stone, gravel, wood, sand, iron
Artificial : brick, concrete, timber
4
Advantageous : fire-resistantce, low cost, durability, hardness, high strength, corrosion-resistance
Disadvantageous : high cost, low resistance, high weight, heavy weight, non-fire-resistance, softness
3
Natural : metal, stone, gravel, wood, sand, iron
Artificial : brick, concrete, timber
4
Advantageous : fire-resistantce, low cost, durability, hardness, high strength, corrosion-resistance
Disadvantageous : high cost, low resistance, high weight, heavy weight, non-fire-resistance, softness