Papers by Author: Qiang Cao

Abstract: A polycarboxylate superplasticizer (PCs) was synthesized by copolymerization of allyl polyoxyethylene ethers (APE), acrylic acid (AA), sodium methylallyl Sulfonate (SMAS) and ethyl acrylate (EA). The effect of functional groups and branch chain on PCs properties was investigated by the test of fluidity of cement paste, retardation performance and Zeta potential of cement particles. The results showed that carboxylic groups and ethyl ester groups can improve water reducing ratio and fluidity of cement paste, and the sulfonic groups has an important contributiion to retardation performance of PCs.

Abstract: Polycarboxylate (PC) superplasticizer was synthesized by radical copolymerization using ammonium persulfate (APS) as initiator at 90 °C for 5 h. The effect of PC on the hydration process and microstructure of hardened cement at different hydration ages (4 h, 1 d and 7 d) was investigated. Hydration of cement paste results show that the nucleation and growth of hydration product of ettringite (Aft) was inhibited by PC at the early hydration ages, and the generation of the hydration products of calcium hydroxide (CH) and calcium carbonate (CaCO3) was promoted at late hydration ages. SEM result indicates that PC can make the structure of hardened cement more homogeneous and more density.

Abstract: Sulfonated chitosan (SCS) was prepared from chitosan and sulfuric acid via sulfation reaction. SCS was used as superplasticizer in cement. The test showed that the maximum fluidity of the cement paste was 232 mm with dosage of 0.75 wt % at water to cement ratio (w/c) of 0.29. Meanwhile, lesser loss of fluidity and slump over 60 mins were observed comparing to naphthalene sulfonated formaldehyde condensates (NSF). A well-distribution of cement particles can be seen from the image of SEM in the sample of mortar prepared by SCS. The water reduce ratio of SCS reach 19.2 %. The applied results showed that SCS could slightly improve the mechanical properties of mortar. The paste fluidity, mechanical properties and slump loss of the cement paste incorporated SCS indicated that it can be used as superplasticizer in concrete.