Early Hydration of Clinker-slag-metakaolin Combination in Steam Curing Conditions, Relation With Mechanical Properties

High strength can be obtained at early ages for precast concrete elements by use of CEMI 52.5R cement (OPC) and thermal treatment (steam curing). To compensate for the announced withdrawal of CEM I cements because of high CO2 emissions during their production and the ecotax that this will imply, one attractive alternative is use of composed cements resulting from the combination of clinker with mineral admixtures. In steam curing conditions, previous studies have shown an increase in the compressive strength at 1 day of age for mortars incorporating an OPC/blast furnace slag (GGBS)/metakaolin (MK) combination, in comparison with mortars incorporating OPC only. This study investigates the connection between compressive strength, at 1 day of age, of steam cured mortars made with various binders and hydration of these binders. The progress of the hydration was characterized by means of XRD, thermal and microprobe analyses. The results indicate that the increase in compressive strength when MK is incorporated (OPC/MK or OPC/MK/GGBS) can be explained by an increase in the amount of C-S-H, C-A-H, C-A-S-H phases, a decrease in the amount of CH, and a change in the chemical nature of the matrix (decrease in C/S ratio). The decrease in compressive strength of OPC/slag-based material can be explained by a reduction in the amount of hydrated phases (particularly C-S-H) and compactness. These are promising results for precast concrete manufacturers who are concerned about preserving the environment.

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  • English

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  • Accession Number: 01147275
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 23 2009 10:06AM