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<p>This study aimed to mitigate the excessive drying shrinkage of alkali-activated slag-fly ash (AASFA) mortar by systematically evaluating the effects of four chemical admixtures—gypsum, calcium sulfoaluminate (CSA) expansive agent, AEO-15, and PEG-400—on workability, mechanical properties, and long-term shrinkage behavior. The applicability of classical shrinkage prediction models, particularly the GL2000 model, was assessed for the AASFA system. Experimental results indicate that these admixtures reduce 56-day drying shrinkage by approximately 40%, 43%, 26%, and 30%, respectively. Gypsum and CSA compensate for shrinkage through chemical expansion driven by ettringite formation, with CSA showing more sustained shrinkage suppression due to its prolonged hydration. AEO-15 alleviates internal tensile stresses via air entrainment, while PEG-400 retards moisture evaporation through hydrogen bonding. In terms of macroscopic performance, both gypsum and CSA improve fluidity and delay setting; at a 6% dosage, they yield 28-day compressive strengths of 48.3&#xa0;MPa and 45.5&#xa0;MPa, respectively. After calibrating the cement-type coefficient K, the GL2000 model exhibits the best agreement with the experimental shrinkage data. This work clarifies the mechanisms by which different admixtures inhibit shrinkage in AASFA systems and provides a theoretical and experimental basis for refining shrinkage-prediction models and designing low-shrinkage alkali-activated mixtures.</p>

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Shrinkage compensation in alkali-activated slag-fly ash mortar: role of chemical additives

  • 期刊论文

  • 发表日期：

    2026年7月8日

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  • Jiantong Wu,
  • Zhirong Jia,
  • Xuejing Wang,
  • Haowei Zhang,
  • Xiaoqian Liu

摘要

This study aimed to mitigate the excessive drying shrinkage of alkali-activated slag-fly ash (AASFA) mortar by systematically evaluating the effects of four chemical admixtures—gypsum, calcium sulfoaluminate (CSA) expansive agent, AEO-15, and PEG-400—on workability, mechanical properties, and long-term shrinkage behavior. The applicability of classical shrinkage prediction models, particularly the GL2000 model, was assessed for the AASFA system. Experimental results indicate that these admixtures reduce 56-day drying shrinkage by approximately 40%, 43%, 26%, and 30%, respectively. Gypsum and CSA compensate for shrinkage through chemical expansion driven by ettringite formation, with CSA showing more sustained shrinkage suppression due to its prolonged hydration. AEO-15 alleviates internal tensile stresses via air entrainment, while PEG-400 retards moisture evaporation through hydrogen bonding. In terms of macroscopic performance, both gypsum and CSA improve fluidity and delay setting; at a 6% dosage, they yield 28-day compressive strengths of 48.3 MPa and 45.5 MPa, respectively. After calibrating the cement-type coefficient K, the GL2000 model exhibits the best agreement with the experimental shrinkage data. This work clarifies the mechanisms by which different admixtures inhibit shrinkage in AASFA systems and provides a theoretical and experimental basis for refining shrinkage-prediction models and designing low-shrinkage alkali-activated mixtures.