Effect of the Side Chain Hydrophobicity on the Properties of Shrinkage-Reducing Polycarboxylate Superplasticizers

摘要

The shrinkage of concrete can adversely affect not only its fitness for use, but also the durability of concrete structural elements. Compared with traditional PCEs, shrinkage-reducing polycarboxylate superplasticizer (SR-PCE) can decrease the concrete shrinkage. Therefore, it s a new way to increase the durability of concrete in recent years. In this paper, three novel SR-PCEs were designed and synthesized by the free radical copolymer-ization of acrylic acid and the macromonomers with hydrophobic poly(ethylene oxide and/ orpropylene oxide)-based side chains. The effect of the side chain hydrophobicity on drying shrinkage and dispersion performance for concrete was investigated, and the relationship between side chainhydrophobicity, drying shrinkage and pore solution properties (surface tension and alkali ions concentration) was also studied. Based on these investigations, a new kind of SR-PCE was developed (SR-PCE3). Upon the addition of 0.4% SR-PCE3, the water-reducing rate was about 21.4% and the drying shrinkage of concrete was decreased by 24.0% at 60 days. Introducing hydrophobic group as the side chain into the polymer may be an effective way to change the properties of pore solution significantly with low concentration of SR-PCE and thus solve the contradiction between adsorption dispersing and shrinkage reducing.