The Influence of Curing Conditions on the Surface Porosity of Polymer-Modified Cements

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Title: The Influence of Curing Conditions on the Surface Porosity of Polymer-Modified Cements

Author(s): N. R. Short and M. K. Salbin

Publication: Special Publication

Volume: 170

Issue:

Appears on pages(s): 1009-1028

Keywords: Acrylic resins; chlorides; curing; diffusion; polymer-cement concretes; porosity; styrene-butadiene resins.

Date: 7/1/1997

Abstract:
Polymer modified cementitious materials are used in construction for applications such as bridge deck overlays and concrete repair. When using this type of material a wet-dry curing regime is usually recommended in order to give optimum mechanical properties. However, such a curing regime is contrary to that which would be expected for a low porosity surface layer, desirable, e.g., for good resistance to chloride ingress. This paper presents the results of investigations into the influence of curing conditions on the surface porosity of polymer modified cements and its influence on chloride diffusivity. Small cement paste prisms were cast and the top faces exposed to: wet, wet-dry, and wet-dry-wet curing regimes. Pore size distributions were then determined for the top, middle and bottom layers using mercury intrusion porosimetry. Results showed that for all mixture proportions the wet-dry curing regime resulted in a surface layer which was more porous and had a coarser pore structure than the deeper layers The extent of this effect depended on: actual curing regime, W/C, and type of polymer latex used. Results were confirmed by determining the effective diffusivity of chloride ions in similar samples.