Phase Formation and Microstructure Properties of Autoclaved Aerated Concrete (AAC) Based on Ceramic and Gypsum Waste (CGW) as Raw Material Addition

Abstract

Pure autoclaved aerated concrete (AAC) and AAC based on ceramic and gypsum waste (CGW) additions have been prepared with different compressive strengths. The compressive strength is 1.64 MPa to 2.39 MPa and the work density is 593.71 kg/m³to 649.57 kg/m³. The phase formation and microstructure properties of AAC have been investigated by powder X-ray diffraction method and field emission scanning electron microscopy (FESEM). The main objective of this work is to determine the linear correlation between compressive strength with phase formation and the microstructure of the sample. The results showed that the AAC sample has four types of phase formation such as quartz phase, tobermorite phase, C-S-H phase, and anhydrate phase. The average crystallite size (D) of the tobermorite phase sample is 5.05% to 22.36%. The highest compressive strength had a linear correlation with the phase formation of the tobermorite and C-S-H. However, the highest compressive strength does not have a linear correlation with the average size (D), average lattice parameter (a), average strain (e), and dislocation density (d). Based on microstructure analysis, the high compressive strength of the sample had a linear correlation with plate-like tobermorite crystalline and closed pore of the sample. Furthermore, the highest compressive strength of the sample had also a linear correlation with the Ca/Si element ratio. Because the AAC-CGW is classified as a grade-2 AAC, the samples are suitable for thermal wall and fire resistance applications.