Effects of curing conditions on properties of concrete using slag replacement

The effects of curing conditions on properties of slag cement concrete were studied. Autoclaving (175 degrees C, 0.5 MPa) and steam curing (80 degrees C) were compared to normal curing (28 days, 20 degrees C, and 100% RH). Four different concrete mix designs with the same mix proportions and different cement replacements were used: 0% slag (control), 25% slag, 50% slag, and 75% slag. The effects of slag replacement and curing conditions upon concrete properties ties were examined. The properties examined included mechanical properties (compressive and tensile strength), transport properties (chloride permeability and chloride penetration), and microstructural properties (pore structure and phase composition). There is little effect of slag replacement up to 50% upon strength, whereas higher replacement results in a drop in compressive strength. Steam curing reduces the compressive strength compared to the other curing types considered in this study. Chloride permeability and penetrability significantly decrease with increasing slag replacement except for autoclave curing, which is the least sensitive with respect to slag replacement compared to the other curing types considered in this study. The addition of slag reduces the continuous pore diameter, which correlates well with the initial current (IC) measured by the rapid chloride permeability test (RCPT). (C) 2000 Elsevier Science Inc. All rights reserved.