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). Fo ur different concrete mix designs with the same mix proportions and differe nt cement replacements were used: 0% slag (control), 25% slag, 50% slag, an d 75% slag. The effects of slag replacement and curing conditions upon conc rete properties ties were examined. The properties examined included mechan ical properties (compressive and tensile strength), transport properties (c hloride permeability and chloride penetration), and microstructural propert ies (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 streng th compared to the other curing types considered in this study. Chloride pe rmeability and penetrability significantly decrease with increasing slag re placement except for autoclave curing, which is the least sensitive with re spect to slag replacement compared to the other curing types considered in this study. The addition of slag reduces the continuous pore diameter, whic h correlates well with the initial current (IC) measured by the rapid chlor ide permeability test (RCPT). (C) 2000 Elsevier Science Inc. All rights res erved.