*2.4.8 Hardness test*

Hardness of the bricks can be found out with the aid of the scratch of the finger nail [5]. If no impression is left over the surface, the brick is treated to be sufficiently hard. All the samples tested showed very slight indentation, which is acceptable. (Please refer to **Figure 6** for the result of the hardness test).

### *2.4.9 Structure test*

In structure test, a brick is broken and its structure is inspected. It is observed that the bricks are compact, homogeneous and free from any imperfections such as lumps, holes, etc. (Please refer to **Figure 7** for the result of the structure test).

**Figure 6.** *Hardness test of geopolymer bricks.*

**Figure 7.** *Structure.*
