Title: Combined Effect of Expansive and Shrinkage Reducing Admixtures on Microstructure of Mortars and Concretes

Author(s): C. Maltese, A. Lolli, C. Pistolesi, A. Bravo, and T. Cerulli

Publication: Symposium Paper

Volume: 234

Issue:

Appears on pages(s): 781-796

Keywords: calcium oxide; expansion; expansive admixture; shrinkage; shrinkage reducing admixture

DOI: 10.14359/15973

Date: 3/22/2006

Abstract:
The dimensional stability of cement based materials (mortar or concrete) may be improved through the use of shrinkage reducers or expansive agents. In this study the combined use of a propylene glycol ether based shrinkage reducer (SRA) and a calcium oxide based expansive admixture has been investigated. Mortar and concrete specimens (prepared without admixtures or with SRA or EXP or SRA and EXP) has been compared through compressive strength determinations, free drying shrinkage, restrained shrinkage and restrained expansion measurements. A synergistic effect on the shrinkage reduction has been observed when the shrinkage reducing admixture and the expansive agent have been used together. In order to elucidate such phenomenon, the hydration of cement pastes containing these kinds of admixtures has been followed by ESEM-FEG (Environmental Scanning Electron Microscopy – Field Emission Gun) and specific surface area measurements.