SAP预吸硅溶胶对内养护水泥基材料性能的影响及机理

Effects and mechanisms of pre-absorption of SAP in colloidal silica sol on the properties of cement-based materials internally-cured

对超吸水树脂(SAP)进行预吸硅溶胶处理,研究了预吸处理对SAP内养护低水灰比水泥基材料性能的影响及机理。研究结果表明:SAP在硅溶胶中吸水时,随硅溶胶质量分数增大,吸水率明显下降;硅溶胶纳米颗粒无法吸附进入SAP半透膜内部,仅吸附于表面,并在水泥基材料水化硬化后,在其表面形成致密C-S-H硬壳层,这两方面因素导致与掺未改性SAP相比,掺改性SAP对低水灰比水泥净浆的减缩效果明显下降,然而SAP表面形成的致密C-S-H硬壳层有助于提升水泥胶砂抗折和抗压强度。

The superabsorbent polymer(SAP)is pre-absorbed by using colloidal silica sol,and the effects and mechanisms of pre-absorption of SAP in colloidal silica sol on the properties of cement-based materials with low water/cement ratio by using SAP as an internal curing agent are investigated.The results show that the water absorption of the SAP decreases significantly with increasing the concentration of silica sol.The silica nanoparticles can not be adsorbed into the semipermeable membrane in SAP,but on the surface.After hydrated and hardened,a dense C-S-H hard shell layer is formed around the surface of the SAP due to pozzolanic reactions.The reduction in water absorption and the formation of the hard C-S-H gel layer cause a reduction in the water release capacity of the SAP,which results in a weaker autogenous shrinkage-reducing effect of the SAP in hardened cement paste with low water-cement ratios,as compared with that with SAP without pre-absorption of the colloidal silica sol.However,the formation of the hard C-S-H gel shell layer helps to improve the flexural and compressive strength of hardened cement mortar effectively.