Abstract The influences of fly ash and metakaolin added as substitutions (by up to 50 wt%) of magnesium potassium phosphate cement (MKPC) on the microstructures and compressive strengths of the MKPC pastes were investigated. The results indicate that the aluminosilicate fractions of both fly ash and metakaolin are involved in the acid-base reaction of MKPC system, leading to a preferential formation of irregular crystalline struvite-K incorporated with Al and Si elements and/or amorphous aluminosilicate phosphate products. Metakaolin is more reactive than fly ash in the MKPC system. For the same addition dosage, the MKPC pastes containing metakaolin exhibit higher compressive strengths than the pastes containing fly ash. This is attributed to the formation of more highly reinforced microstructures and denser interfaces between the metakaolin particle and hydration products (e.g. struvite-K) in the MKPC paste containing metakaolin. Addition of 30 wt% metakaolin increases the compressive strengths of MKPC pastes at all test ages.

中文翻译：

---

粉煤灰和偏高岭土对磷酸镁钾水泥浆体微观结构和抗压强度的影响

摘要 研究了粉煤灰和偏高岭土作为磷酸镁钾水泥 (MKPC) 的替代品（最高 50 wt%）对 MKPC 浆体的微观结构和抗压强度的影响。结果表明，粉煤灰和偏高岭土的铝硅酸盐部分都参与了 MKPC 体系的酸碱反应，导致优先形成不规则结晶鸟粪石-K 与 Al 和 Si 元素和/或无定形铝硅酸盐磷酸盐产物。在 MKPC 系统中，偏高岭土比飞灰更具反应性。对于相同的添加量，含偏高岭土的 MKPC 糊料比含粉煤灰的糊料具有更高的抗压强度。这归因于在含有偏高岭土的 MKPC 糊剂中偏高岭土颗粒和水合产物（例如鸟粪石-K）之间形成了更高强度的微结构和更致密的界面。添加 30 wt% 的偏高岭土可提高 MKPC 糊剂在所有测试龄期的抗压强度。