Cements based on hydrated magnesium carbonates are an alternative binder system with high CO2 sequestration ability. The present study examines the effect of silica, a by-product of MgO production from magnesium-silicate rocks, in MgO/nesquehonite binders. A high Mg/Si ratio of 3 was used to allow the formation of both the hydrous carbonate-containing brucite (HCB) phase and the magnesium silicate hydrate (M-S-H) phase. HCB formed within the first day. Its quantity was reduced during the formation of M-S-H and stabilized until the complete reaction of silica. Low quantities of nesquehonite, ≤10 wt%, accelerated M-S-H formation, while ≥16 wt% hindered it. CO2 quantification showed that up to 12 g of CO2 per 100 g dry cement could be sequestered. MgO/silica/nesquehonite mortars with 10 wt% of nesquehonite and a water/cement ratio of 0.65 exhibited overall good mechanical strength, achieving 23 MPa at 2 days and 36 MPa at 182 days.

中文翻译：

---

Nesquehonite 和二氧化硅对镁-硅酸盐-碳酸盐水泥的影响


基于水合碳酸镁的水泥是一种具有高 CO2 封存能力的替代粘合剂系统。本研究考察了二氧化硅（镁硅酸盐岩石中生产 MgO 的副产品）在 MgO/nesquehonite 粘合剂中的影响。使用 3 的高 Mg/Si 比值来形成含水碳酸盐水镁石 （HCB） 相和硅酸镁水合物 （M-S-H） 相。HCB 在第一天形成。其量在 M-S-H 的形成过程中减少并稳定直至二氧化硅完全反应。少量的 nesquehonite，≤10 wt%，加速了 M-S-H 的形成，而 ≥16 wt% 则阻碍了它的形成。CO2 定量表明，每 100 g 干水泥最多可封存 12 g CO2。MgO/二氧化硅/烯氟石砂浆的 nesquehonite 含量为 10 wt%且水灰比为 0.65，表现出良好的整体机械强度，在 2 天时达到 23 MPa，在 182 天时达到 36 MPa。