**3. Discussions**

*Geopolymers and Other Geosynthetics*

*2.4.10 Scanning electron microscopy*

from defects such as holes and lumps.

From the images of the scanning electron microscope (SCM) as seen in **Figures 8** and **9**, it is observed that the bricks are homogeneous, compact and free

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**Figure 9.**

*SEM image of GB-4.*

**Figure 8.**

**Figure 7.** *Structure.*

*SEM image of GB-1.*

In this work a series of tests were carried out to study the strength and durability properties of the geopolymer bricks. Also field tests were conducted to check the quality of bricks.

The following are the key points of the discussions:

The compressive strength of the geopolymer bricks is more for the mix which has higher concentration of the alkaline solution, i.e. 10 M as compared to 8 M and which has the highest percentage of Slag sand.

The compressive strength is minimum for the geopolymer bricks, which were having the least percentage of slag sand and with the highest percentage of iron ore tailings. The highest water absorption percentage obtained also showed the same pattern.

The dimensionality test results were within the Indian Standard code recommendations. In falling test, failure of the geopolymer bricks was not severe and maximum pattern failures were restricted to mild edge failure, moderate edge failure and no failure.

The efflorescence test conducted proved that the bricks were prone to efflorescence slightly. Thus, it satisfied the statement "Efflorescence shall not be more than Slight for Higher class bricks" as all the bricks belong to class AA category, the highest category.

The geopolymer bricks produced clear ringing sound when struck with another brick and proved to be sound and good. The bricks when subjected to hardness test by scratching with a nail did not leave any impressions on the surface and proved to be sufficiently hard.

The structure test and the scanning electronic microscope (SCM) conducted on geopolymer bricks helped to understand the microstructure level of the bricks. The bricks are homogeneous, compact and free from defects such as holes, lumps etc.
