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1960275 
Journal Article 
Interaction between alpha-calcium sulfate hemihydrate and superplasticizer from the point of adsorption characteristics, hydration and hardening process 
Guan, B; Ye, Q; Zhang, J; Lou, W; Wu, Z 
2010 
Yes 
Cement and Concrete Research
ISSN: 0008-8846 
40 
2 
253-259 
WOS:000274221600009 
Superplasticizers (SPs), namely sulfonated melamine formaldehyde (SMF) and polycarboxylate (PC), were independently admixed with alpha-calcium sulfate hemihydrate based plaster to improve the material's performance. SMF and PC gave, respectively, 38% and 25% increases in the 2 h bending strength at the optimum dosages of 0.5 wt.% and 0.3wt.%, which are determined essentially by the maximum water-reducing efficiency. The peak shift of binding energy of Ca2P(3/2) detected by X-ray photoelectron spectroscopy (XPS) suggests that SPs are chemically adsorbed on gypsum surface. A careful examination of the strength development of set plaster allowed the hydration and hardening process to be divided roughly into five stages. SMF accelerates early hydration, while PC decelerates it. Both SPs allowed similar maximum water reductions, giving a more compact structure and a decrease in total pore volume and average pore diameter, and thus leading to higher strengths in the hardened plasters with SPs. (C) 2009 Elsevier Ltd. All rights reserved. 
alpha-calcium sulfate hemihydrate (D); Superplasticizer (D); Adsorption (C); Hydration (A); Hardening (A)