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

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 Ca²⁺ 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.