Synthesis Amphoteric Polycarboxylate Superplasticizer Without Chloride Ion And Its Properties Study

Cement superplasticizers agent are essential to improve the concrete performance of auxiliary material, and also are the hot areas of research at present.The cement mineral compositions are complex, there are not only negative Zeta potential of mineral compositions, such as tricalcium silicate（C₃S） and dicalcium silicate（C₂S）, but also positive Zeta potential of mineral compositions, such as tricalcium aluminate（C₃A） and tetracalcium alumino- ferrite（C4AF）. Amphoteric polycarboxylate superplasticizers, introducing some cationic groups into traditional PCEs copolymer, have been designed to overcome the shortcoming of low saturation dosage of traditional anionic po lycarboxylate superplasticizers（PC Es）, which mainly absorb on the surface of C 3A and C4 AF. Among present literatures, the cationic monomer such as [3-（methacryloylamino） propyl] trimethylammonium chloride（MAPTAC）, diallyldimethyl ammonium chloride（DMDAAC）, methacryloxyethyltrimethyl ammonium chloride（DMC）, 2-（3-carboxy-acryloyloxy）-N-（carboxymethyl）-N,N-dimethylethanaminium（C AC） were often used to synthesize amphoteric polycarboxylate superplasticizers. Nevertheless, these kind of cationic monomers often have chloride ion, which may lead to the corrosion of steel bar in concrete.In this paper, a good dispersing performance of traditional anionic polycarboxylate superplasticizers SPCA1-0 was synthesize by acrylic acid（AA）, isobutylene polyoxyethylene ether（HPEG-2400） with initiator of ammonium persulfate（APS）. Then a self-synthesized amphoteric monomer without chloride, which was named sulfopropyl betaine 3-Sulfo-N, N-dimethyl-N-（2’-methacryloyloxyethyl）-propanaminium Inner Salt（SPB）, and commercia l cationic monomer（DMC） were respectively to replace the monomer AA of SPCA1-0 to synthesize amphoteric polycarboxylate superplasticizers series, which were named as SPCA（with monomer SPB） and DPCA（with DMC monomer）. According to the results of fluidity of cement paste, the SPCA series had a better dispersing performance than the DPCA series.When the SPB monomer was replaced 10% of AA monomer of SPCA1-0, the amphoteric polycarboxylate superplasticizers of SPCA9-1 was synthesized, which had a high water-reducing rate. When the dosage of SPCA9-1 was 0.3%, its water-reducing rate of cement paste was 43%, which was 5% higher that of SPCA1-0, and 10% higher that of DPCA9-1.This study carried out isothermal calorimetry、TGA、XRD and SEM to study SPCA9-1, DPCA9-1 and SPCA1-0 on the early age properties of cement pastes. The isothermal calorimetry results showed that SPCA1-0, SPCA9-1 and DPCA9-1 could decreased the 75%, 86% and 77% heat amount than that of blank cement（195.08J/g） at1d; and SPCA1-0, SPCA9-1 and DPCA9-1 could decreased the 7%, 21% and 10% heat amount than that of blank cement（275.06J/g） at 3d. It showed SPCA9-1 could decrease much of the heat amount. The XRD results revealed that SPCA9-1, DPCA9-1 and SPCA1-0 could retard the hydration of cement at the early time, but the amount hydrates at the 7d of cement with SPCA9-1 and DPCA9-1 were the same as that of the blank cement, and the TG results approved the XRD results. The SEM results showed that SPCA9-1 could compacted cement paste structure, there were a lot of flocculent growth ettringite in cement structure, and the compressive strength at 7d was up to 44.3Mpa.This study also studied the tolerance of different type PCEs to Na-montmorillonite（Na-Mmt）, when the SPCA1-0、SPCA9-1 、DPCA1-0 was respectively added to the cement containing 1% Na-Mmt clay systems, decrease of the initial fluidity of cement paste were 19%, 4% and 5%, decrease of the 1h fluidity of cement paste were 32%, 7% and 24%. The SPCA9-1 and DPCA9-1 showed good tolerance to Na-Mmt clay at initial time, and SPCA9-1 could keep a good dispersion performance after 1h. The affect of the Na- montmorillonite to the dispersion performances of SPCA9-1、DPCA9-1 and SPCA1-0 were study with IR、XRD、UV and TG. The results showed that the cationic monomer（SPB and DMC） could improve the tolerance to Na-montmorillonite caly, especially the SPB monomer which had a steric hindrance could help PCEs keep good dispersion performances in cement system with pollution of the Na-Mmt clay.