Durability and Microstructure of Phosphogypsum-Slag-Based All-Solid-Waste Cementitious Material Regulated by Red Mud and Recycled Cement Powder

doi:10.16552/j.cnki.issn1001-1625.2025.1258

Abstract

Abstract:

In this paper， phosphogypsum-slag-based all-solid-waste cementitious material was developed using phosphogypsum （PG）， slag， recycled cement powder （RCP）， red mud （RM）， and quicklime. The individual and synergistic effects of RCP and RM on mechanical properties， durability， and microstructure were characterized. The results indicate that the incorporation of RCP and RM significantly enhances the mechanical properties and durability of the cementitious material. The specimen with 10% （mass fraction） RCP and 10% （mass fraction） RM exhibits relatively superior performance. In comparison to the PG-slag-based system， the 28 d compressive strength and flexural strength increase by 57.1% and 57.4%， reaching 43.2 and 7.4 MPa， respectively. Simultaneously， the non-steady-state chloride migration coefficient and drying shrinkage decrease by 42.5% and 43.6%， while the sulfate corrosion resistance coefficient is elevated from 73.6% to 85.6%. RCP serves as a physical filler and provides chemical activity， offering nucleation site and active component for the hydration reaction. Additionally， RM raises the alkalinity of the system and introduces extra aluminosilicate minerals， which accelerates the dissolution and polymerization of precursors， and stimulates the potential pozzolanic activity of RCP. RCP and RM synergistically promote the formation of calcium aluminosilicate hydrate gel and maintain a considerable amount of ettringite， consequently optimizing the composition of hydration products， ultimately achieving a comprehensive improvement in pore structure densification and macroscopic performance. This study is expected to provide a technical reference for the development of green cementitious materials and the resource utilization of solid waste.

Key words: phosphogypsum, all-solid-waste cementitious material, red mud, recycled cement powder, durability, microstructure

CLC Number:

TU528

LIU Xin, LI Mingyang, ZHANG Xihe, LAN Shaoding, GAO Xu. Durability and Microstructure of Phosphogypsum-Slag-Based All-Solid-Waste Cementitious Material Regulated by Red Mud and Recycled Cement Powder[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(7): 2478-2490.

Figures/Tables 14

Fig.1 XRD patterns of cementitious material

Table 1 Main chemical composition of cementitious material

Material	Mass fraction/%
Material	CaO	SiO₂	Al₂O₃	SO₃	Na₂O	K₂O	Fe₂O₃	P₂O₅	MgO	LOI
GGBS	33.80	31.00	12.30	2.23	0.59	0.73	1.01	0.03	7.96	2.37
PG	40.78	5.60	0.36	51.88	—	0.09	0.28	0.71	0.06	0.12
RCP	47.53	23.53	8.98	2.41	0.61	0.81	2.02	0.06	1.65	10.12
RM	15.37	21.20	23.42	1.89	9.02	1.86	19.04	0.32	1.64	2.56

Fig.2 Particle size distribution of cementitious material

Table 2 Mix proportion of phosphogypsum-slag-based all-solid-waste cementitious material

Sample No.	Binder composition/%				Lime content/%	Water-binder ratio	Binder-sand ratio （mortar）	Concrete composition/（kg·m^-3）
Sample No.	PG	GGBS	RCP	RM	Lime content/%	Water-binder ratio	Binder-sand ratio （mortar）	Binder	Fine aggregate	Coarse aggregate
Ref	50	50	—	—	4	0.45	1∶3	450	720	1 080
RP1	40	50	10	—	4	0.45	1∶3	450	720	1 080
RP2	30	50	20	—	4	0.45	1∶3	450	720	1 080
RM1	40	50	—	10	4	0.45	1∶3	450	720	1 080
RM2	30	50	—	20	4	0.45	1∶3	450	720	1 080
RPM1	40	50	5	5	4	0.45	1∶3	450	720	1 080
RPM2	30	50	10	10	4	0.45	1∶3	450	720	1 080

Fig.3 Workability of fresh mortar

Fig.4 Mechanical properties of phosphogypsum-slag-based all-solid-waste mortar

Fig.5 Relation between compressive strength and flexural strength of phosphogypsum-slag-based all-solid-waste mortar

Fig.6 Chloride penetration resistance of phosphogypsum-slag-based all-solid-waste concrete

Fig.7 Drying shrinkage property of phosphogypsum-slag-based all-solid-waste mortar

Fig.8 Sulfate attack test results of each phosphogypsum-slag-based solid waste concrete specimens

Fig.9 XRD patterns of specimens

Fig.10 TG-DTG curves of specimens

Fig.11 FTIR spectra of paste specimens

Fig.12 SEM images and EDS results of different all-solid waste systems

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