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. 2024 Sep 18;17(18):4580.
doi: 10.3390/ma17184580.

Effects of Dolomitic Limestone on the Properties of Magnesium Oxysulfate Cement

Juan Camilo Adrada Molano  1 , Adriano Galvão Souza Azevedo  1 , Taís Oliveira Gonçalves Freitas  1 , Gabriela Casemiro Da Silva  2 , Holmer Savastano Jr  1
Affiliations

Effects of Dolomitic Limestone on the Properties of Magnesium Oxysulfate Cement

Juan Camilo Adrada Molano et al. Materials (Basel). .

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.

Keywords: active magnesium oxide (a-MgO); compressive strength; dolomitic limestone; magnesium oxysulfate cement; standardized hydration method.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Particle size distributions of the raw materials used.
Figure 2
Figure 2
Setting time of MOS cement pastes (a) and hydration kinetics of light-burned MgO (LBM) (b).
Figure 3
Figure 3
Compressive strength of the MOS cement pastes cured for 7 and 28 days.
Figure 4
Figure 4
Diffractograms of the MOS cement pastes cured for 7 (left) and 28 (right) days.
Figure 5
Figure 5
Thermogravimetric curves of MOS cement pastes after 7 days of air curing.
Figure 6
Figure 6
Thermogravimetric curves of MOS cement pastes after 28 days of air curing.
Figure 7
Figure 7
Mass loss of each component of MOS cement pastes at 7 and 28 days of air curing.
Figure 8
Figure 8
Isothermal calorimetry curves for MOS cement pastes.
Figure 9
Figure 9
Cumulative hydration heat of MOS cement pastes.
Figure 10
Figure 10
The hydration mechanism of MOS at acceleration period with (A) and without dolomitic limestone (B). Adapted from [38].
Figure 11
Figure 11
Fractured surface morphology of MOS samples after 28 days of curing.
Figure 11
Figure 11
Fractured surface morphology of MOS samples after 28 days of curing.
Figure 12
Figure 12
Apparent porosity of MOS cement pastes after curing for 7 days.
See this image and copyright information in PMC

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