改善磷酸镁水泥砂浆(MPCM)的韧性有利于促进其在混凝土结构加固和修复领域的应用。为了增强MPCM的韧性,对比研究了未处理和硝酸预处理碳纤维对 MPCM力学性能的影响,分析了碳纤维增韧 MPCM的机制。结果表明,当碳纤维质量掺量为0.4%时,MPCM 7 d抗折强度增大44.5%；3~6 mm碳纤维有利于提高MPCM的抗压强度,而6~10 mm碳纤维更有利于提高 MPCM的抗折强度；未处理碳纤维与磷酸镁水泥(MPC)水化产物之间为物理作用,碳纤维未能充分发挥增韧效果；在40~60℃、浓度68%的硝酸中浸泡30~60 min有利于改善碳纤维与MPC水化产物的界面粘结,使预处理后的碳纤维和MPC水化产物产生嵌合作用,显著增强了MPCM的力学性能和韧性。
Toughening magnesium phosphate cement mortar (MPCM)will boost the application of MPCM in concrete structure reinforcement and repair.Aiming to toughen MPCM,the effect of untreated and pretreated carbon fibers on the mechanical properties of MPCM was studied,and the toughening mechanism of carbon fibers was ana-lyzed.The results show that the flexural strength of MPCM increased by 44.5% with the addition of 0.4% carbon fi-bers.Carbon fibers with a length of 3-6 mm was conducive to improving the compressive strength of MPCM,and carbon fibers with a length of 6-10 mm could contributed to the flexural strength of MPCM.The properties of MPCM toughened by untreated carbon fibers had no obvious improvement,because of the physical bonding between untreated carbon fibers and hydration products of MPC.Pretreated carbon fibers which were immersed in 68% nitrite acid solution at 40-60 ℃ for 60 min,were beneficial to promoting the interface bonding between carbon fibers and hydration products of MPC.Based on chimerical reaction between hydration products and pretreated carbon fibers,the mechanical properties and toughness of MPCM were significantly improved.
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