铜离子掺杂对水泥水化的影响机理

Influence Mechanism of Copper Ion Doping on Cement Hydration

本文研究了铜离子对熟料矿相种类、结构和水化进程的影响机理。结果表明:铜离子对水泥水化进程的缓凝抑制作用按照影响机理分为两个阶段:第一阶段,铜离子掺杂导致水化体系中Ca^(2+)浓度降低,早期氢氧化钙(Cu(OH)_2)结晶形成受阻,破坏了反应溶液的高碱性环境,且钙矾石(Aft)的形成速率减小、生成量减少,诱导期延长,水化产物间无法快速搭接形成网状结构,水泥浆体凝结硬化受阻;第二阶段,铜离子造成C_3S晶粒异常长大,水化反应活性降低,水泥浆体结构变得疏松、孔隙率增大,从而导致其后期强度显著降低,且孔隙中分布晶体尺寸较大的钙矾石,相互穿插,形成水泥浆体中的薄弱联结。

Influence mechanism of copper ions on the clinker mineral composition、crystal structure and hydration process were studied systematically by means of advanced techniques including nuclear magnetic resonance（NMR）.Results show that：Retarding and inhibition effect of copper ion on cement hydration process is divided into two stages according to the influence mechanism：（1）in the initial and induction period：With the incorporation of copper ion,the concentration of Ca^2＋ in the hydration system is reduced,calcium hydroxide（Cu（OH）2）crystal formation is blocked,and consequently the high alkaline environment of the reaction solution is destroyed.Besides above,the Ca^2＋ concentration reduction decreases the formation rate and content of Ettringite（AFt）,extending the induction period.The hydration products cannot be quickly lapped to form a mesh structure.（2）in the acceleration period：Copper ion leads to an abnormal growth of C3S grains,and lowers the hydration activity of the C3S.The structure of cement pastes becomes loose and porous.Finally,the strength of the cement paste lowers significantly.Besides,interspersing and larger size ettringite distributes in pores work together to form weak links in the cement pastee.