| Recently, the solid Polycarboxylate Superplasticizer(SPC) had received more attention infiled of water-reducer of cement due to its unique advantages comparing with liquid SPC suchas conveniences in stocking and transportation and it widely apply to dry mortar, sprayedconcrete and high-grade ceramic. So far, most powdery or particulate SPC were from resultantprepared by aqueous polymerization at high temperature through spray drying method, andthere has not been report about solid SPC obtained through precipitation method by one step.In this paper, allyl polyoxyethylene ether-56(APEG-56) was used to synthesis liquidresultant by a queous polymerization, and we discuss the separating out of SPC from differentamout of precipitant, and we ensure the mixture of tetrahydrofuran(THF) and acetic ether(EA)as poor solvent for our resultant. The abrasiveness, water-solubility and storage stability ofSPC are tested to determine whether the scheme is feasible. Then APEG-56, AA and Methylsulfonic acid(MAS) were used to synthesis the SPC with potassium Persulfate (KPS) asinitiator by aqueous polymerization to get a appropriate monomer ratio. Then we useammonium persulfate(APS) which has strong oxidability and fast initiation rate instead of KPSto further optimize the experiment.In order to optimize the experiment, modified polyether TPEG instead of APEG-56, AAand Methllyl sulfonic acid(MAS) were choosed to synthesis the SPC with APS as initiator.With the flowability of cement paste and flowability retentivity of Ordinary Portland Cement42.5(P.O42.5) as valuation criteria, results showed the optimum experiment condition wasthat the molar ratio of TPEG, AA, and MAS was at0.8:3.25:0.4, and the weight ratio of APSwas at1%of monomers. Experiment condition:80℃, AA and APS were added dropwiseduring2h and2.5h respectively and heat preservation for1.5h. The mercaptoacetic acid wasadded as chain transfer agent to adjust molecular weight of SPC, and the best dispersibility andretentivity of cement were obtained when the weight ratio of mercaptoacetic acid reached0.25‰of monomers.In this dissertation, the experiment under the best conditions was repeated enlarge severaltimes, and results showed that this method is repeatable by testing flowability of original paste. Compared with Power Polycarboxylate Superplasticizer(PPC) on the market, SPC synthesizedvia precipitation polymerization shows better dispersibility, dispersion stability, andperformance, otherwise the effect of SPC on zeta potential on cement particles is no differentfrom the same amout of PPC’s, although it is worse than LPC in water-reducing rate for mortarand concrete. It was proved that the scheme that modified polyether TPEG was used tosynthesize SPC with the mixture of THF and EA as precipitant is feasible and producible bytesting the abrasiveness, water-solubility and storage stability of SPC. |
