基于低场核磁共振技术研究骨料粒径对混凝土水化及孔隙水分布的影响

Study the effect of aggregate size on the hydration and pore water distribution of concrete based on low-field NMR technology

通过低场核磁共振技术研究不同骨料粒径混凝土的水化特征。通过核磁共振τ2谱得出水化过程中的等效平均孔隙半径、孔隙水分布、传输程度、水化程度以及水化速率,从而进一步探究骨料粒径对混凝土水化的影响。结果表明:水化过程中试样的τ2谱整体左移,在水化反应进行10 h后胶凝孔和过渡孔对应的峰合并成1个峰。同时,我们通过核磁共振τ2谱及等效平均孔隙半径追踪水化期间试件内的水分分布及迁移传输路径,在前2 h水分主要是由毛细孔经过过渡孔转移到胶凝孔,在2~6 h内毛细孔中传输来的水分主要储存在过渡孔中,而在6 h以后,毛细孔中的水分基本转移到胶凝孔和过渡孔中参与水化反应。另外,骨料粒径影响混凝土早期水化反应及孔隙分布,颗粒级配组成越复杂,水化程度及速率越高,水化期间孔径越连续,小骨料粒径更易生成小的孔隙,且水化程度及速率与骨料粒径呈负相关关系。

It aims to study the hydration characteristics of concrete with different aggregate sizes by low-field NMR technology.Through nuclear magnetic resonanceτ2 spectrum,the equivalent average pore radius,pore water distribution and transmission,hydration degree and hydration rate in the hydration process are obtained,so as to further explore the influence of aggregate size on concrete hydration.The results show that theτ2 spectrum of the sample shifts to the left as a whole during the hydration process,and the peaks corresponding to the gel pores and transition pores merge into one peak after 10 h of hydration reaction.At the same time,it tracked the water distribution and migration and transmission path in the specimen during hydration by nuclear magnetic resonanceτ2 spectrum and equivalent average pore radius.In the first 2 h,water is mainly transferred from capillary pores to gel pores through transition pores.From 2 h to 6 h,the water transferred from capillary pores is mainly stored in transition pores.After 6 h,the water in the capillary pores is basically transferred to the cementitious pores and transition pores to participate in the hydration reaction.In addition,the aggregate size affects the early hydration reaction and pore distribution of concrete.The more complex the particle gradation composition,the higher the degree and rate of hydration,the more continuous the pore size during hydration,and the smaller the aggregate size,the easier it is to generate small pores,and the degree and rate of hydration are negatively correlated with the aggregate size.