Effects of Dolomitic Limestone on the Properties of Magnesium Oxysulfate Cement

Author(s)

Molano, Juan Camilo Adrada ; Azevedo, Adriano Galvao Souza ; Freitas, Tais Oliveira Goncalves ; Da Silva, Gabriela Casemiro ; Savastano Jr, Holmer

• Document type: Journal article
• Source: MATERIALS; v. 17, n. 18, p. 16-pg., 2024-09-01.

Abstract

This study investigated the effects of substituting magnesium oxide (MgO) with dolomitic limestone (DL) on the mechanical and physical properties of magnesium oxysulfate (MOS) cement. Additionally, the hydration formation phases and the influence of the molar ratio on the MOS cement's performance were examined. The corresponding action mechanisms were identified and explored by compressive strength tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), isothermal calorimetry, and a thermogravimetric analysis (TGA). The results showed that replacing MgO with DL decreased the reaction speed and heat release rate generated in the hydration process of the MOS cement. This substitution also reduced the quantity of non-hydrated MgO particles and delayed the formation of Mg(OH)2. The diminished formation of Mg(OH)2 contributed to an increase in the apparent porosity of pastes containing DL, thus alleviating internal stresses induced by Mg(OH)2 formation and enhancing their mechanical strength after 28 days of curing. Conversely, the increased porosity improved the CO2 diffusion within the structure, promoting the formation of magnesium carbonates (MgCO3). Through the characterization of the cement matrix (XRD and TGA), it was possible to identify phases, such as the brucite, periclase, and 318 phases. The obtained results revealed the potential of incorporating mineral fillers like limestone as a promising approach to producing MOS cement with a reduced environmental impact and better properties at higher curing ages. (AU)

• FAPESP's process: 24/02445-4 - Use of nucleation seeds to enhance CO2 capture and mineralization from the sugar and ethanol industry in low-carb fiber-cement
• Grantee: Adriano Galvão de Souza Azevedo
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 23/04412-3 - Development of Basic Magnesium Sulphate Cement composites (BMSC) for Engineering applications
• Grantee: Juan Camilo Adrada Molano
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/50948-3 - INCT 2014: advanced eco-efficient technologies in cementitious products
• Grantee: Vanderley Moacyr John
• Support Opportunities: Research Projects - Thematic Grants