硅烷减水剂对水化硅酸钙晶核粒径调控

Effect of Organosilane-Modified Polycarboxylate Superplasticizers on Grain Size of Calcium Silicate Hydrate Seeds

为了获得稳定分散的水化硅酸钙(C-S-H)晶核,提高其对水泥水化的晶核诱导效应,实现水泥熟料的高效利用,采用自由基聚合制备出了结构中含有不同比例丙烯酸(AA)和硅烷基团(KH570)的聚羧酸分散剂(PCE),通过溶液沉淀法合成了相应C-S-H/PCE晶核。分别测试了C-S-H/PCE晶核粒径分布、稳定性、晶核界面结合方式。结果表明,硅烷减水剂显著增加了C-S-H/PCE晶核的稳定性。在PCE分子结构中引入适当比例的KH570能有效调控C-S-H/PCE晶核粒径,随着KH570比例的增加,PCE在C-S-H表面的吸附方式由Ca^(2+)络合向更加稳定的Si—O—Si化学键合方式转变,C-S-H/PCE晶核粒径先减小后增大。当KH570:AA比例为1时,PCE在C-S-H表面的吸附层厚度最大(2.5 nm),制备的C-S-H/PCE晶核粒径最小(60 nm)和稳定性最佳,继续增加KH570比例,PCE在碱性条件下发生PCE分子内脱水缩合过程,形成网状的硅树脂结构,对C-S-H/PCE晶核粒径调控不利。

In order to obtain stable and dispersed calcium silicate hydrate(C-S-H)crystal nucleus,improve its crystal nucleus-inducing effect on cement hydration,and realize the efficient utilization of cement clinker.Polycarboxylate superplasticizers(PCE)with different proportions of acrylic acid(AA)and silane group(KH570)were prepared via free radical polymerization to disperse calcium silicate hydrate(C-S-H)seeds.The corresponding C-S-H/PCE seeds were synthesized by a solution precipitation method.The grain size/size distribution,the stability of C-S-H/PCE seeds and the bonding mode of PCE on C-S-H interface were investigated.The results show that the PCE with an appropriate proportion of KH570 can effectively control the grain size of C-S-H/PCE seeds.The adsorption mode of PCE on C-S-H surface changes from Ca^(2+)complexation to a more stable Si—O—Si chemical bond,and the grain size of C-S-H/PCE seeds firstly decreases and then increases with the increase of KH570 ratio.At a KH570 to AA ratio of 1,the adsorption layer thickness of PCE on the surface of C-S-H is 2.5 nm,the grain size of C-S-H/PCE seeds is 60 nm and the stability is optimum.The PCE undergoes an intramolecular dehydration condensation process under alkaline condition with further increasing the proportion of KH570,forming a reticulated silicone resin structure,which is unfavorable for the regulation of grain size of C-S-H/PCE seeds.