Magnesium and potassium phosphate cement （MKPC） sample were prepared by mixing dead burnt MgO powder, potassium phosphate and different dosages of retarder borax to investigate the effect of borax on its hydration a...Magnesium and potassium phosphate cement （MKPC） sample were prepared by mixing dead burnt MgO powder, potassium phosphate and different dosages of retarder borax to investigate the effect of borax on its hydration and hardening characteristics. The pH value, fluidity, hydration temperature and strength development of MKPC paste were investigated, and the mineralogical composition and microstructural morphology of its hydration products were analyzed. The experimental results indicated that, within a certain dosage, borax caused an endothermal effect for MKPC paste, which decreased the early hydration rate of MKPC paste, increased the fluidity of MKPC paste. Thus, strength and micro-morphology of hardened MKPC are affected. It can be concluded that borax in MKPC paste retards the early hydration rate of MKPC paste by forming a film onto surface of MgO, decreasing the temperature and increasing the pH value of the system. As borax dosage varying, different factors may dorminate the effects.展开更多
Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and waves.To ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS...Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and waves.To ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS)are mixed to repair damaged structures on coral islands.However,CS is significantly different from land-sourced sand in mineral composition,particle morphology,and strength.This has a substantial impact on the hydration characteristics and macroscopic properties of MKPC mortar.Therefore,in this study we investigated the compressive strength,interfacial mechanical properties,and corrosion resistance of MKPC CS mortar.Changes in the morphology,microstructure,and relative contents of hydration products were revealed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)and X-ray diffraction(XRD).The results indicated that the compressive strength increased linearly with the interfacial micro-hardness,and then stabilized after long-term immersion in pure water and Na2SO4 solution,showing excellent corrosion resistance.Compared with MKPC river sand(RS)mortar,the hydration products of CS mortar were an intermediate product 6KPO2·8H2O with a relative content of 3.9%at 1 h and 4.1%at 12 h.The hydration product MgKPO_(4)·6H_(2)O increased rapidly after 7-d curing,with an increased growth rate of 1100%.Our results showed that CS promoted the nucleation and formation of hydration products of MKPC,resulting in better crystallinity,tighter overlapping,and a denser interfacial transition zone.The results of this study provide technical support for applying MKPC mortar as a rapid repair material for damaged structures on coral islands.展开更多
采用磷酸二氢钠(SDP)部分替代磷酸二氢钾制备磷酸镁水泥,研究磷酸二氢钠对磷酸镁水泥负温环境早期力学性能的影响。研究结果表明,磷酸二氢钠可以缩短磷酸镁水泥凝结时间,当磷酸二氢钠用量质量分数达到75%时,磷酸镁水泥净浆的最终凝结时...采用磷酸二氢钠(SDP)部分替代磷酸二氢钾制备磷酸镁水泥,研究磷酸二氢钠对磷酸镁水泥负温环境早期力学性能的影响。研究结果表明,磷酸二氢钠可以缩短磷酸镁水泥凝结时间,当磷酸二氢钠用量质量分数达到75%时,磷酸镁水泥净浆的最终凝结时间为6 min 30 s。-10℃环境下,当磷酸二氢钠完全替代磷酸二氢钾时,MPC基材料的增强效果最好,但凝结时间却最短,不足6min。复合磷酸二氢钠和磷酸二氢钾可提高MPC的早期抗折强度及粘接强度,且磷酸二氢钠的质量分数在0~50%,粘接强度随着磷酸二氢钠含量的增加而增加;当磷酸二氢钠质量分数高于50%时,粘接强度开始下降。展开更多
文摘Magnesium and potassium phosphate cement （MKPC） sample were prepared by mixing dead burnt MgO powder, potassium phosphate and different dosages of retarder borax to investigate the effect of borax on its hydration and hardening characteristics. The pH value, fluidity, hydration temperature and strength development of MKPC paste were investigated, and the mineralogical composition and microstructural morphology of its hydration products were analyzed. The experimental results indicated that, within a certain dosage, borax caused an endothermal effect for MKPC paste, which decreased the early hydration rate of MKPC paste, increased the fluidity of MKPC paste. Thus, strength and micro-morphology of hardened MKPC are affected. It can be concluded that borax in MKPC paste retards the early hydration rate of MKPC paste by forming a film onto surface of MgO, decreasing the temperature and increasing the pH value of the system. As borax dosage varying, different factors may dorminate the effects.
基金This work is supported by the Key Technologies R&D Program of Guangxi Zhuang Autonomous Region(No.GUIKE AB22080073)the Open Research Program of State Key Laboratory of Geomechanics and Geotechnical Engineering(No.SKLGME021026),China.
文摘Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and waves.To ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS)are mixed to repair damaged structures on coral islands.However,CS is significantly different from land-sourced sand in mineral composition,particle morphology,and strength.This has a substantial impact on the hydration characteristics and macroscopic properties of MKPC mortar.Therefore,in this study we investigated the compressive strength,interfacial mechanical properties,and corrosion resistance of MKPC CS mortar.Changes in the morphology,microstructure,and relative contents of hydration products were revealed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)and X-ray diffraction(XRD).The results indicated that the compressive strength increased linearly with the interfacial micro-hardness,and then stabilized after long-term immersion in pure water and Na2SO4 solution,showing excellent corrosion resistance.Compared with MKPC river sand(RS)mortar,the hydration products of CS mortar were an intermediate product 6KPO2·8H2O with a relative content of 3.9%at 1 h and 4.1%at 12 h.The hydration product MgKPO_(4)·6H_(2)O increased rapidly after 7-d curing,with an increased growth rate of 1100%.Our results showed that CS promoted the nucleation and formation of hydration products of MKPC,resulting in better crystallinity,tighter overlapping,and a denser interfacial transition zone.The results of this study provide technical support for applying MKPC mortar as a rapid repair material for damaged structures on coral islands.
文摘采用磷酸二氢钠(SDP)部分替代磷酸二氢钾制备磷酸镁水泥,研究磷酸二氢钠对磷酸镁水泥负温环境早期力学性能的影响。研究结果表明,磷酸二氢钠可以缩短磷酸镁水泥凝结时间,当磷酸二氢钠用量质量分数达到75%时,磷酸镁水泥净浆的最终凝结时间为6 min 30 s。-10℃环境下,当磷酸二氢钠完全替代磷酸二氢钾时,MPC基材料的增强效果最好,但凝结时间却最短,不足6min。复合磷酸二氢钠和磷酸二氢钾可提高MPC的早期抗折强度及粘接强度,且磷酸二氢钠的质量分数在0~50%,粘接强度随着磷酸二氢钠含量的增加而增加;当磷酸二氢钠质量分数高于50%时,粘接强度开始下降。
