Effect of Accelerator and Early Strength Agent on Properties of Shotcrete

doi:10.16552/j.cnki.issn1001-1625.2025.0921

Abstract

Abstract:

In view of the problems of ordinary shotcrete， such as prolong setting time and slow development rate of extremely early strength， a self-made setting accelerator and early strength agent was employed for modification. The effects of accelerator and early strength agent on setting time of cement paste， workability and mechanical properties of shotcrete were investigated， and the modification mechanism was analyzed by means of tests such as hydration heat， X-ray diffraction （XRD）， thermogravimetric （TG-DTG） and scanning electron microscopy （SEM）. The results show that the in corporation of the accelerator and early strength agent slightly reduces the workability of concrete， it can significantly improve the setting accelerator effect and mechanical properties of shotcrete. When the dosage of the accelerator and early strength agent is 4%（mass fraction）， its slump decreases to 185 mm. Compared with the group without the accelerator and early strength agent， the initial setting time and final setting time are shortened by 50.0% and 45.5% respectively. The compressive strength at 3 h， 8 h， 1 d and 28 d increased by 128.6%， 79.7%， 26.7% and 2.6% respectively. Mechanism analysis indicates that the sulphoaluminate clinker and nanomaterials in the accelerator and early strength agent can significantly accelerate the hydration process of the cement paste， promoting the formation of hydration products such as needle-rod-like ettringite （AFt） and flocculent calcium silicate hydrate （C-S-H） gel， and make the internal structure of the concrete more dense， thereby effectively improving the accelerating setting effect and mechanical properties of shotcrete.

Key words: shotcrete, accelerator and early strength agent, setting time, workability, mechanical property, modification mechanism

CLC Number:

TU528.53

LI Shunkai, CHEN Ronghui, DONG Xun, DOU Huakang, SUN Fengpin. Effect of Accelerator and Early Strength Agent on Properties of Shotcrete[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(4): 1184-1192.

Figures/Tables 15

References 25

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Performance indicator	Solid mass fraction/%	pH value	Initial setting time/min	Final setting time/min	Compressive strength/MPa
Performance indicator	Solid mass fraction/%	pH value	Initial setting time/min	Final setting time/min	1 d	28 d
Measured value	49.0	2.21	4.3	10.6	7.3	46.7

Performance indicator	Solid mass fraction/%	pH value	Initial setting time/min	Final setting time/min	Compressive strength/MPa
Performance indicator	Solid mass fraction/%	pH value	Initial setting time/min	Final setting time/min	1 d	28 d
Measured value	49.0	2.21	4.3	10.6	7.3	46.7

Sample No.	Mix ratio/（kg·m^-3）
Sample No.	Cement	Water	Accelerator and early strength agent	Accelerator
A0	400	140	0	24
A1	400	140	4	24
A2	400	140	8	24
A3	400	140	12	24
A4	400	140	16	24
A5	400	140	20	24

Sample No.	Mix ratio/（kg·m^-3）
Sample No.	Cement	Water	Accelerator and early strength agent	Accelerator
A0	400	140	0	24
A1	400	140	4	24
A2	400	140	8	24
A3	400	140	12	24
A4	400	140	16	24
A5	400	140	20	24

Sample No.	Mix proportion/（kg·m^-3）
Sample No.	Cement	Water	Sand	Stone	Water reducer	Accelerator andearly strength agent	Accelerator
C0	479	187	876	808	4.79	0	28.74
C1	479	187	876	808	4.79	4.79	28.74
C2	479	187	876	808	4.79	9.58	28.74
C3	479	187	876	808	4.79	14.37	28.74
C4	479	187	876	808	4.79	19.16	28.74
C5	479	187	876	808	4.79	23.95	28.74