Rapid Assessment of Shrinkage Performance and Its Mechanism of Alkali-Activated Slag via Vacuum Dehydration

doi:10.16552/j.cnki.issn1001-1625.2026.0012

Abstract

Abstract:

Aiming at the problems of large shrinkage rate and long test cycle of alkali-activated slag （AAS）， this study used vacuum dehydration technology to quickly evaluate its shrinkage performance， and studied the influence mechanism of vacuum dehydration temperature （40， 50， 60 ℃） on the shrinkage performance and microstructure of AAS. By monitoring the dynamic changes of AAS internal relative humidity and pore solution surface tension， combined with multi-scale microscopic analysis technology， the coupling law of temperature-moisture migration-structure evolution was revealed. The results show that vacuum dehydration significantly changes the shrinkage process of AAS. The early shrinkage of AAS is accelerated， and the total shrinkage rate at 28 d is significantly reduced. The shrinkage reduction effect after 40 ℃ treatment is the best. Moderate temperature rise （ 40 to 50 ℃） can promote the removal of free water and optimize the pore structure. The increased capillary pressure can effectively reduce the shrinkage stress in the early viscoplastic stage of AAS material through the synergistic effect of pore size optimization and creep dissipation. However， too high temperature （60 ℃） will cause the capillary pressure accumulation rate to exceed the creep dissipation capacity， causing stress-strain mismatch， which in turn induces microcracks and increases porosity.

Key words: alkali-activated slag, vacuum dehydration, rapid shrinkage evaluation, creep effect, capillary pressure, pore structure

CLC Number:

TQ177

TIAN Chenglong, TAO Yuan, LIU Leping, XIANG Jichun, CUI Xuemin, HE Yan. Rapid Assessment of Shrinkage Performance and Its Mechanism of Alkali-Activated Slag via Vacuum Dehydration[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(7): 2379-2388.

Figures/Tables 12

References 27

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Sample	Activator	Na₂O content/%	W/B	Dehydration time/h	Temperature/℃
NH-CG	NaOH	5	0.35	—	—
NH-VD-40				6，12，18，24	40
NH-VD-50				6，12，18，24	50
NH-VD-60				6，12，18，24	60
WG-CG	Waterglass			—	—
WG-VD-40				6，12，18，24	40
WG-VD-50				6，12，18，24	50
WG-VD-60				6，12，18，24	60

Sample	Activator	Na₂O content/%	W/B	Dehydration time/h	Temperature/℃
NH-CG	NaOH	5	0.35	—	—
NH-VD-40				6，12，18，24	40
NH-VD-50				6，12，18，24	50
NH-VD-60				6，12，18，24	60
WG-CG	Waterglass			—	—
WG-VD-40				6，12，18，24	40
WG-VD-50				6，12，18，24	50
WG-VD-60				6，12，18，24	60

Sample	Surface tension/（mN·m^-1）
Sample	0 h	6 h	12 h	18 h	24 h
NH-CG	59.4	55.1	44.8	40.4	39.6
NH-VD-40	59.4	48.8	45.4	48.4	53.8
NH-VD-50	59.4	54.0	57.7	53.8	56.9
NH-VD-60	59.4	62.5	59.4	57.9	52.5
WG-CG	47.0	46.7	41.9	42.2	51.0
WG-VD-40	47.0	49.3	48.2	46.9	52.7
WG-VD-50	47.0	48.4	47.6	45.0	54.5
WG-VD-60	47.0	53.9	49.3	47.3	41.5

Sample	Surface tension/（mN·m^-1）
Sample	0 h	6 h	12 h	18 h	24 h
NH-CG	59.4	55.1	44.8	40.4	39.6
NH-VD-40	59.4	48.8	45.4	48.4	53.8
NH-VD-50	59.4	54.0	57.7	53.8	56.9
NH-VD-60	59.4	62.5	59.4	57.9	52.5
WG-CG	47.0	46.7	41.9	42.2	51.0
WG-VD-40	47.0	49.3	48.2	46.9	52.7
WG-VD-50	47.0	48.4	47.6	45.0	54.5
WG-VD-60	47.0	53.9	49.3	47.3	41.5

Item	NH-CG	NH-VD-40	NH-VD-50	NH-VD-60	WG-CG	WG-VD-40	WG-VD-50	WG-VD-60
Calcite content/%	46.23	48.28	52.35	58.34	45.09	58.82	61.14	57.82
Hydrotalcite content/%	1.15	1.29	1.42	1.33	0.09	0.21	0.31	0.40