沸石对海水拌合超高性能混凝土性能的影响

利用沸石部分或完全(体积分数为0%、50%、100%)取代海水拌合超高性能混凝土(UHPC)中的河砂,对比研究了沸石对海水拌合UHPC宏观和微观性能的影响。结果表明,海水拌合促进UHPC的水化,从而缩短UHPC的凝结时间,提高UHPC的抗压强度和自收缩,而沸石吸收氯离子会抑制氯离子的加速水化作用,使海水拌合UHPC的凝结时间延长,抗压强度降低。此外,沸石的内养护作用可以有效改善海水拌合UHPC的自收缩,且效果比在淡水拌合UHPC中更好,这主要是因为沸石在海水拌合UHPC中释水的时间更早且更长。由于多孔沸石的强度低于河砂,所以UHPC的早期抗压强度随着沸石含量的增多而逐渐降低,养护至28 d后,沸石的内养护作用优化了界面过渡区,从而促使后期硬化浆体进一步密实。

Effect of Zeolite on Properties of Seawater Mixing Ultra-High Performance Concrete ( UHPC)

Zeolite was utilized to partially or completely (0%, 50%, 100%, volume fraction) replace river sand and the effect of zeolite on the macro and micro properties of seawater mixing ultra-high performance concrete (UHPC) was studied. The flowability, setting time, autogenous shrinkage and compressive strength of UHPC were tested. Besides, the water absorption and water releasing of zeolite as well as the interfacial transition zone (ITZ) of UHPC were studied by low field NMR and nano-indentation. The results reveal that seawater mixing enhances the hydration of UHPC, so it shortens the setting time, increases the compressive strength and the autogenous shrinkage of UHPC. However, zeolite absorbs chloride ions, which inhibits the accelerated hydration induced by chloride ions, extends the setting time of UHPC and reduces the compressive strength. In addition, the internal curing effect of zeolite effectively improves the autogenous shrinkage of seawater mixing UHPC, and its optimization effect is better than that in freshwater mixing UHPC. The phenomenon can be attributed to the earlier and longer releasing water time of zeolite in seawater mixing UHPC. As the strength of porous zeolite is lower than that of river sand, the early compressive strength of seawater mixing UHPC gradually decreases with the increase of zeolite content. After curing 28 d, because the internal curing effect of zeolite optimizes the interfacial transition zone, the later hardening paste is further compacted.