Molano Juan Camilo Adrada, Azevedo Adriano Galvão Souza, Freitas Taís Oliveira Gonçalves, Silva Gabriela Casemiro Da, Savastano Holmer
Department of Biosystems Engineering, University of São Paulo, Pirassununga 13635-900, SP, Brazil.
Polytechnic School, University of São Paulo, São Paulo 05508-010, SP, Brazil.
Materials (Basel). 2024 Sep 18;17(18):4580. doi: 10.3390/ma17184580.
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). The diminished formation of Mg(OH) contributed to an increase in the apparent porosity of pastes containing DL, thus alleviating internal stresses induced by Mg(OH) formation and enhancing their mechanical strength after 28 days of curing. Conversely, the increased porosity improved the CO diffusion within the structure, promoting the formation of magnesium carbonates (MgCO). 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.
本研究调查了用白云石（DL）替代氧化镁（MgO）对硫酸镁氧（MOS）水泥力学性能和物理性能的影响。此外，还研究了水化生成相以及摩尔比对MOS水泥性能的影响。通过抗压强度试验、扫描电子显微镜（SEM）、X射线衍射（XRD）、等温量热法和热重分析（TGA）确定并探究了相应的作用机制。结果表明，用DL替代MgO降低了MOS水泥水化过程中产生的反应速度和放热速率。这种替代还减少了未水化MgO颗粒的数量，并延迟了Mg(OH)的形成。Mg(OH)形成量的减少导致含DL浆体的表观孔隙率增加，从而减轻了由Mg(OH)形成引起的内部应力，并提高了养护28天后的机械强度。相反，孔隙率的增加改善了结构内的CO扩散，促进了碳酸镁（MgCO）的形成。通过对水泥基体的表征（XRD和TGA），可以识别出诸如水镁石、方镁石和318相之类的相。所得结果揭示了掺入石灰石等矿物填料作为一种有前景的方法来生产对环境影响较小且在较高养护龄期具有更好性能的MOS水泥的潜力。
