CUED Publications database

Strength and drying shrinkage of slag paste activated by sodium carbonate and reactive MgO

Jin, F and Al-Tabbaa, A (2015) Strength and drying shrinkage of slag paste activated by sodium carbonate and reactive MgO. Construction and Building Materials, 81. pp. 58-65. ISSN 0950-0618

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Abstract

© 2015 Elsevier Ltd. All rights reserved. This paper investigates the potential of combining Na 2 CO 3 and reactive MgO as a sustainable activator for ground granulated blastfurnace slag. Two very different reactivity MgOs were added at 5-10 % and the Na 2 CO 3 content varied from 4% to 8% by the weight of slag. The strength and drying shrinkage of the activated slag pastes were tested up to 90 d. It was found that the optimum reactive MgO addition was 5% regardless of the MgO type and Na 2 CO 3 content. MgO with the higher reactivity significantly increased the early strength of the paste but had almost no effect on the strength at 90 d. On the other hand, the effect of the lower reactivity MgO on the strength was more profound at later ages and low Na 2 CO 3 dosage. In terms of drying shrinkage, increasing the Na 2 CO 3 content from 4% to 6% caused a remarkable decrease of drying shrinkage while increasing it from 6% to 8% had negligible effect. X-ray diffraction and thermogravimetric analysis revealed that the major hydration products were calcium silicate hydrate gel and hydrotalcite-like phases, similar to those in conventional alkali-activated slag cements. There was also a large quantity of calcite formed especially in the 8% Na 2 CO 3 pastes due to causticisation. It was concluded that the combination of reactive MgO and Na 2 CO 3 could serve as a potential sustainable activator for slags.

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div D > Geotechnical and Environmental
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 18:59
Last Modified: 14 Sep 2017 01:27
DOI: