Microstructure analyses of autoclaved ground dune sand–Portland cement paste

• Autoclaved 30% GDS mixture yielded compressive strength comparable to control mixture cured under normal conditions.
• The microstructure analyses reveal how GDS contributes to the strength and physical properties of the autoclaved mixtures.
• SEM and EDX showed the clear formation of dense and newly formed thin crystalline of CSH with a low CaO/SiO2 ratio.
• XRD, DTA and TGA analyses revealed that the portlandite phase is consumed in GDS autoclaved mixtures.

In this study, SEM, EDX, XRD, DAT and TGA are used to perform microstructure analyses of autoclaved ground dune sand–ordinary Portland cement (GDS–OPC) pastes. Pastes containing 0%, 10%, 20%, 30% and 40% GDS as cement replacement were prepared for this purpose. The microstructure analyses were used to examine the microscale changes that occur in the GDS–OPC pastes with increasing GDS replacement levels. The SEM and EDX results showed the clear formation of dense and newly formed thin crystalline calcium silicate hydrate with a low CaO/SiO2 ratio. The XRD, DTA and TGA analyses revealed that the portlandite phase had been eliminated. The microstructure analyses reveal how GDS contributes to the strength and physical properties of concrete.