Influence of the molar ratios CaO/SiO2 contained in the sustainable microcomposites on the mechanical and microstructural properties of (Ca, Na)-poly(sialate-siloxo) networks

The sustainable microcomposites with different molar ratios CaO/SiO2 such as 0, 0.4, 0.6, 0.8, 1.0 and 1.2 were prepared using calcined brown chicken eggshell, rice husk ash and distilled water. 10 wt% of each microcomposite was used to substitute metakaolin and the obtained calcium aluminosilicate materials were used for investigating the effects of the molar ratios CaO/SiO2 in the microcomposites on the physical, mechanical and microstructural properties of (Ca, Na)-poly (sialate-siloxo) networks. Commercial sodium waterglass and sodium waterglass from rice husk ash with a molar ratio SiO2/Na2O kept constant at 1.6 were used as chemical ingredients. Each (Ca, Na)-poly (sialate-siloxo) network was obtained by mixing each calcium aluminosilicate material with each hardener. The final products were characterized by infrared spectroscopy and X-ray diffractometry. The determination of the apparent density, compressive strength and scanning electron microscopy analysis were done. The results show that the compressive strength values of geopolymer cements using hardener from rice husk ash and microcomposites containing the molar ratios CaO/SiO2 equal to 0, 0.4, 0.6, 0.8, 1.0 and 1.2 are 64.01, 67.97, 66.15, 65.09, 60.73 and 49.40 MPa, respectively. Whereas, those from commercial sodium waterglass are 64.75, 69.03, 64.64, 56.73, 36.47 and 28.30 MPa, respectively. It was found that the most convenient molar ratio CaO/SiO2 in the structure of microcomposite required for producing (Ca, Na)-poly (sialate-siloxo) networks with higher mechanical properties is around 0.4.