乙烯基可再分散聚合物对水泥水化产物的影响

Effects of Vinyl Redispersible Polymer on Cement Hydration Products

利用步进扫描X线衍射、磁共振、场发射环境扫描电镜分析了乙烯基可再分散聚合物对72 h水泥水化产物的影响.结果表明:乙烯基可再分散聚合物能显著延缓水泥水化产物钙矾石、氢氧化钙以及C-S-H凝胶的生成时间,降低其生成量,且水化24 h内的降幅尤其显著.掺入10%(质量分数)乙烯基可再分散聚合物后,钙矾石生成时间由几分钟延迟到3 h以上,氢氧化钙和C-S-H凝胶开始生成时间由水化3 h延迟到9 h,在相同水化时间下氢氧化钙和C-S-H凝胶的含量明显低于纯水泥浆体.乙烯基可再分散聚合物能显著影响C-S-H凝胶的结构和形貌,促进C-S-H凝胶硅氧四面体由一聚态向高聚态转变,且转变时间由水化24 h提前到12 h,导致C-S-H凝胶表面气孔明显增多.

The effects of vinyl redispersible polymer（VRP） on the hydration products of cement pastes within hydration time of 72 h were investigated through step scanning X-ray diffraction（XRD）,（）^（29）Si nuclear magnetic resonance（NMR） and environmental scanning electron microscopy（ESEM） techniques.The results show that VRP postpones the formation time of crystalline ettringite（AFt）,calcium hydroxide（Ca（OH）_2） and calcium silicate hydrate（C-S-H） gel of cement pastes,and decreases the content of these three hydration products,especially within the hydration time of 24 h. The formation of AFt is delayed from several minutes to about 3 h.The formation of Ca（OH）_2 and C-S-H gel is delayed about 6 hours,and the content of Ca（OH）_2 and C-S-H gel is remarkably less than that in pure cement paste at the same hydration time.VRP also obviously affects the structure and the morphology of C-S-H gel.VRP facilitates the transformation of tetrahedron polymerization in C-S-H gel from monomers Q^0 to Q^1 and Q^2,and accelerates the transformation time of tetrahedron polymerization from 24 h to 12 h.Lots of pores entrained by VRP formed in C-S-H gel of cement pastes.