Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub>
Delayed strength development and long setting times are the main disadvantageous properties of Na<sub>2</sub>CO<sub>3</sub>-activated slag cements. In this work, combined auxiliary activators of Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> were incorporat...
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| Online Access: | https://www.mdpi.com/1996-1944/15/5/1687 |
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| author | Lilan Xie Kaiwei Liu |
| author_facet | Lilan Xie Kaiwei Liu |
| author_sort | Lilan Xie |
| collection | DOAJ |
| description | Delayed strength development and long setting times are the main disadvantageous properties of Na<sub>2</sub>CO<sub>3</sub>-activated slag cements. In this work, combined auxiliary activators of Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> were incorporated in one-part Na<sub>2</sub>CO<sub>3</sub>-activated slag binders to accelerate the kinetics of alkali activation. The properties and microstructure evolution were investigated to clarify the reaction mechanism. The results showed that the additions of auxiliary activators promoted the hardening of the pastes within 2 h. The 28 days compressive strengths were in the range of 39.5–45.5 MPa, rendering the binders practical cementitious materials in general construction applications. Ca(OH)<sub>2</sub> was more effective than Mg(OH)<sub>2</sub> in accelerating the kinetics of alkali activation. The dissolution of Ca(OH)<sub>2</sub> released more OH<sup>−</sup> and Ca<sup>2+</sup> ions in the aqueous phase to increase alkalinity in the aqueous phase and promote the formation of the main binding gel phase of calcium-aluminosilicate hydrate (C-A-S-H). An increase in the Ca(OH)<sub>2</sub>/Mg(OH)<sub>2</sub> ratios increased autogenous shrinkage and decreased drying shrinkage of the binders. The formation of a compact pore structure restricted the water evaporation from the binders during the drying procedure. |
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| id | doaj.art-e01f92f151454595a576625c4d02d131 |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-09T20:33:31Z |
| publishDate | 2022-02-01 |
| publisher | MDPI AG |
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| spelling | doaj.art-e01f92f151454595a576625c4d02d1312023-11-23T23:17:17ZengMDPI AGMaterials1996-19442022-02-01155168710.3390/ma15051687Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub>Lilan Xie0Kaiwei Liu1School of Materials and Architectural Engineering, Guizhou Normal University, Guiyang 550001, ChinaAnhui Province Engineering Laboratory of Advanced Building Materials, Anhui Jianzhu University, Hefei 230601, ChinaDelayed strength development and long setting times are the main disadvantageous properties of Na<sub>2</sub>CO<sub>3</sub>-activated slag cements. In this work, combined auxiliary activators of Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> were incorporated in one-part Na<sub>2</sub>CO<sub>3</sub>-activated slag binders to accelerate the kinetics of alkali activation. The properties and microstructure evolution were investigated to clarify the reaction mechanism. The results showed that the additions of auxiliary activators promoted the hardening of the pastes within 2 h. The 28 days compressive strengths were in the range of 39.5–45.5 MPa, rendering the binders practical cementitious materials in general construction applications. Ca(OH)<sub>2</sub> was more effective than Mg(OH)<sub>2</sub> in accelerating the kinetics of alkali activation. The dissolution of Ca(OH)<sub>2</sub> released more OH<sup>−</sup> and Ca<sup>2+</sup> ions in the aqueous phase to increase alkalinity in the aqueous phase and promote the formation of the main binding gel phase of calcium-aluminosilicate hydrate (C-A-S-H). An increase in the Ca(OH)<sub>2</sub>/Mg(OH)<sub>2</sub> ratios increased autogenous shrinkage and decreased drying shrinkage of the binders. The formation of a compact pore structure restricted the water evaporation from the binders during the drying procedure.https://www.mdpi.com/1996-1944/15/5/1687alkali-activated slagone-part geopolymersodium carbonateauxiliary activatorshrinkage |
| spellingShingle | Lilan Xie Kaiwei Liu Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> Materials alkali-activated slag one-part geopolymer sodium carbonate auxiliary activator shrinkage |
| title | Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> |
| title_full | Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> |
| title_fullStr | Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> |
| title_full_unstemmed | Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> |
| title_short | Properties and Microstructure of Na<sub>2</sub>CO<sub>3</sub>-Activated Binders Modified with Ca(OH)<sub>2</sub> and Mg(OH)<sub>2</sub> |
| title_sort | properties and microstructure of na sub 2 sub co sub 3 sub activated binders modified with ca oh sub 2 sub and mg oh sub 2 sub |
| topic | alkali-activated slag one-part geopolymer sodium carbonate auxiliary activator shrinkage |
| url | https://www.mdpi.com/1996-1944/15/5/1687 |
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