Alkali-Aggregate Expansion Corrected with Portland-Slag Cement


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Title: Alkali-Aggregate Expansion Corrected with Portland-Slag Cement

Author(s): Federico Barona De La O

Publication: Journal Proceedings

Volume: 47

Issue: 3

Appears on pages(s): 545-552

Keywords: no keywords

Date: 3/1/1951

Granulated basic blast furnace slag meeting ASTM Spec. C205 should not be considered a pozzolan, but a latent cement with a high siliceous glass content requireing the presence of hydrated lime and gypsum for hydration. To correct alkali-aggregate expansion, a high proportion of slag (50 to 60 percent) should be used, which does not reduce strength, rather than lower percentages (20 to 30) which can not be exceeded with pozzolans unless strength is sacraficed. Corrective action was investigated using Pyrex glass as a reative aggregate, and NaOH to increase the alkali content of the different cements and blends into the same high value (1.23 percent). Under similar conditions, with the same high alkali content, much smaller expansions were obtained with slag blends than with straight portlands. It is not intended to compare or recommend the use of slag instead of pozzolans, or the use of portland-blast furnace slag cement, sinece in each case, the availablity, cost and special conditions will determine what to use. In many cases, slag can be used advantageuosly to replace 50 to 60 percent to portland clinker.