纳米SiO_(2)-水泥复合胶凝材料早期水化动力学研究

Early hydration kinetics research of nano-SiO_(2)and cement composite cementitious materials

采用纳米SiO_(2)(NS)部分取代水泥的方式,对比研究NS对于NS-水泥复合胶凝体系的初终凝时间、水泥胶砂抗压强度、抗折强度和水化热等的影响。使用水化热分析NS-水泥复合胶凝体系的水化特性,并基于Krstulović-Dabić水化动力学模型,分析NS-水泥复合胶凝体系的水化反应机理。结果表明:NS取代水泥掺入后,使水泥的初终凝时间提前,提高了水泥胶砂不同龄期的抗压强度,但会降低水泥胶砂的流动度;NS促进NS-水泥复合胶凝体系水化反应的诱导前期、诱导期、加速期和减速期的反应速率,并在减速期出现第三个放热峰,使得加速期和减速期提前结束;NS显著提高结晶成核和晶体生长(NG)、相边界反应(I)和扩散阶段(D)的反应程度,降低I阶段在整个水化进程的占比,加快I阶段向D阶段转变,使得浆体内部孔隙率和渗透率降低,水化反应阻力增加,稳定期提前。

The effects of nano-SiO_(2)(NS)on the initial and final setting time,compressive strength,flexural strength and hydration heat of NS cement composite cementitious system were studied by partial replacement of cement with nano NS.The hydration characteristics of NS cement composite cementitious system were analyzed by hydration heat,and the hydration reaction mechanism of NS cement composite cementitious system was analyzed based on Krstulović-DabićHydration kinetics model.The results showed that after replacement of cement with nano NS,the initial and final setting time of cement was advanced,the compressive strength of cement mortar at different ages was improved,but the fluidity of cement mortar was reduced.NS promoted the reaction rate of the hydration reaction of NS cement composite cementitious system in the early induction period,induction period,acceleration period and deceleration period,and the third exothermic peak appeared in the deceleration period,which made the acceleration period and deceleration period end ahead of schedule.NS significantly improved the reaction degree of crystal nucleation and crystal growth(NG),phase boundary reaction(I)and diffusion stage(D),reduced the proportion of stage I in the whole hydration process,speeded up the transformation from stage I to stage D,reduced the porosity and permeability in the slurry,increased the hydration resistance and advanced the stability period.