*2.3.4 Microstructural analysis*

To ascertain the morphological features of geopolymer concrete made with new combination of fine aggregates, micro structural analysis becomes essential.

**Figure 6.** *Flexural strength test of Prisms.*

The test results would reveal the factors affecting the mechanical properties. Presently available micro structural analysis include Scanning Electron Microscope (SEM), X Ray Diffraction Analysis (XRD), Energy Dispersive Spectroscopy (EDS) or Energy Dispersive X-Ray Analysis (EDAX) etc. In the present investigation, SEM and EDAX were used for the purpose for all mixes.

## *2.3.4.1 Energy dispersive X-ray analysis (EDAX)*

EDAX shall very well be utilised to obtain the elemental composition or chemical characterisation of an area of interest on a specimen. The EDX or EDAX spectrum displays spectra showing peaks corresponding to the energy levels of elements making up the true composition of samples being analysed as received by X-rays. An excitation source, X-ray detector, pulse processor and the analyser constitute the primary components of EDAX. It is also possible to get elemental mapping of a sample as well image analysis. Samples of all proportions were made ready in powder form for analysis. For better accuracy, quantitative correction procedures are need to be applied.

### *2.3.4.2 Scanning electron microscopy (SEM)*

In SEM, the surface of specimens will be scanned with a focused beam of electrons and images would be produced. The atoms in the sample will be interacted by the electrons and produce signals giving information regarding the topography of surface and composition of the sample. Resolution in the range of even 1 nanometer shall be achieved with the help of SEM.

A scanning electron microscope within built energy dispersive X-ray analysis (SEM- EDX) serves as good supplement to the optical microscope in examining new, old and deteriorated concrete. SEM analysis was done both for the samples having combination of fine aggregates (DMS and M-Sand) as well for samples with DMS alone. Samples for SEM analysis were collected from destructed pieces.

Thus, various tests as discussed above were conducted on geopolymer mortar as well on geopolymer concrete specimens conforming to relevant codal provisions.
