Study of SiO2/Al2O3 and CaO/SiO2 relationships in alkali-activated cements

Abstract

Abstract This study investigates alkali-activated cements (AAC), comprising blast furnace slag (BFS) along with industrial by-products like rice husk ash (RHA) and metakaolin (MK), activated by sodium hydroxide (NaOH). The aim is to assess the impact of SiO2/Al2O3 and CaO/SiO2 ratios on AAC's mechanical strength and hydrated compounds. Mechanical and microstructural tests were carried out. Compositions with a CaO/SiO2 ratio near 1 exhibited superior mechanical strength, approximately 35–40 MPa at 28 days, while the SiO2/Al2O3 ratio did not significantly affect the outcomes. X-ray diffraction and thermal analysis revealed the formation of hydrated calcium silicate (CSH) and hydrotalcite as hydrated compounds. This suggests that BFS can enhance AAC results. In conclusion, CaO/SiO2 ratios play a crucial role in influencing the strength gains of AAC. Verifying the influence of these relationships can contribute to the study of dosage and understanding of hydration processes.

Keywords

• alkali activated cement
• slag
• rice husk ash
• CaO/SiO2
• SiO2/Al2O