Synergistic Effect of MgO-Based Expansive Agent and Shrinkage-Reducing Admixture on Compensating the Shrinkage of Cementitious Materials

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Title: Synergistic Effect of MgO-Based Expansive Agent and Shrinkage-Reducing Admixture on Compensating the Shrinkage of Cementitious Materials

Author(s): Z. Zhibin, X. Lingling, and T. Minshu

Publication: Special Publication

Volume: 262

Issue:

Appears on pages(s): 395-406

Keywords: expansive admixture; MgO; shrinkage; shrinkage-reducing admixtures.

Date: 10/1/2009

Abstract:
In order to improve dimensional stability of cementitious materials, synergistic effect of shrinkage reducing admixtures (mixture of glycol ethers and siloxane, SRA) and MgO-based expansive agent (MEA) burned at 850, 950, 1050 and 1200°C (1560, 1740, 1920, and 2190°F) for 1 h on the deformation of cement paste cured in water and sealed by polyethylene sheet at 20, 40 and 60°C (68, 104, and 140°F) was investigated. The results illustrated that combined use of MEA(850~950) and SRA could compensate the shrinkage of cement paste effectively, MEA also could make up for the shortage of SRA whose shrinkage-reducing ratio decreased at later age. Then hydration of MEA in the present of SRA was examined by DSC/TG and gravimetry. The results indicated that the presence of SRA retarded the hydration of MEA because SRA decreased the polarity of solvent and adsorbed on the surface of MEA, but with prolonged curing, the hydration degree of MEA with or without SRA tended to be the same.