聚羧酸系减水剂对铝酸三钙-石膏体系早期水化的作用机制

Mechanism of polycarboxylate superplasticizer on early hydration of tricalcium aluminate⁃gypsum systems

为探究聚羧酸系减水剂(PCE)对铝酸三钙(C_(3)A)-石膏体系早期水化的作用机制,通过水化进程、溶解速率、物相演变和溶液离子浓度进行表征,分析PCE对C_(3)A-石膏体系早期水化的影响机理.结果表明:PCE的掺入抑制了C_(3)A颗粒的溶解,阻碍了钙矾石(AFt)晶体在C_(3)A颗粒表面的成核生长,并使石膏处于较低的溶解平衡状态;PCE在颗粒表面的吸附改变了SO_(4)^(2-)、Ca^(2+)等的空间分布,促使各种离子在颗粒表面的聚集,增加了离子之间碰撞、沉淀,有利于形成单硫型水化硫铝酸钙(AFm)物相.

The mechanism of polycarboxylate superplasticizer(PCE)on the early hydration of tricalci⁃um aluminate(C_(3)A)-gypsum system was investigated.The influence mechanism of PCE on the early hydration of C_(3)A-gypsum system was analyzed by characterizing the hydration process,dissolution rate,phase evolution and solution ion concentration.The results show that the incorporation of PCE in⁃hibits the dissolution of C_(3)A particles,hinders the nucleation and growth of ettringite(AFt)crystals on the surface of C_(3)A particles,and keeps the gypsum in a lower dissolution equilibrium state.The ad⁃sorption of PCE on the particles changes the spatial distribution of SO_(4)^(2-),Ca^(2+),etc.leading to the pore solution is not consistent with the ion concentration on the particle surface,which promotes the aggregation of various ions on the particle surface,increases the collision and precipitation among i⁃ons,and is conducive to the formation of monosulphate(AFm)phase.