*2.4.6 Efflorescence test*

The efflorescence is caused due to the presence of alkalis in bricks. When the bricks get exposed to moisture, water is absorbed by them. Due to evaporation this water absorbed dries out from the exposed faces. As a result of this, the soluble

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**Figure 6.**

*Hardness test of geopolymer bricks.*

*Geopolymer Bricks Using Iron Ore Tailings, Slag Sand, Ground Granular Blast Furnace Slag…*

salts contained within them crystallize out on to the surface. This process continues for several years depending on the amount of salts present in the bricks and their solubility. All the samples tested showed very slight effloresce which is acceptable.

The soundness test is conducted by striking two bricks against each other or by a light hammer [5]. If the bricks generate a clear metallic ringing sound and do not break, then those are good quality bricks. All the samples tested for soundness showed that they are heavy and good causing a metallic ringing sound when struck

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

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).

acceptable. (Please refer to **Figure 6** for the result of the hardness test).

*DOI: http://dx.doi.org/10.5772/intechopen.81748*

(Please refer to **Figure 5**).

*Efflorescence test of geopolymer bricks.*

*2.4.7 Soundness test*

**Figure 5.**

against each other.

*2.4.8 Hardness test*

*2.4.9 Structure test*

**Figure 4.** *Falling test of geopolymer bricks.*

*Geopolymer Bricks Using Iron Ore Tailings, Slag Sand, Ground Granular Blast Furnace Slag… DOI: http://dx.doi.org/10.5772/intechopen.81748*

#### **Figure 5.** *Efflorescence test of geopolymer bricks.*

salts contained within them crystallize out on to the surface. This process continues for several years depending on the amount of salts present in the bricks and their solubility. All the samples tested showed very slight effloresce which is acceptable. (Please refer to **Figure 5**).
