Synergistic Carbonation-Hydration Mechanisms and Microstructural Evolution in Low-Heat Cement and Steel Slag Mortars

doi:10.16552/j.cnki.issn1001-1625.2025.0810

Abstract

Abstract:

The carbonation of ordinary cementitious material has been extensively studied， whereas the carbonation behavior of low-heat Portland cement combined with steel slag remains insufficiently explored. Steel slag， rich in free CaO and latent hydraulic activity， can promote carbonation reactions when incorporated into low-heat cement systems. In this study， the effects of binder-sand ratio， water-binder ratio， and steel slag dosage on compressive strength， pore structure， and phase evolution under different carbonation durations and curing regimes were investigated. Results show that appropriate pre-curing regulates the residual water-binder ratio， enhances CO₂ diffusion， and improves carbonation efficiency. At a binder-sand ratio of 3∶5 with a low water-binder ratio， specimens nearly completely carbonized within 48 h， with calcite as the main carbonation product. The formation of aragonite depending on the carbonation rate. Compressive strength correlates well with carbonation degree， reaching up to 68.8 MPa after 48 h of carbonation. Pore structure analysis indicate that carbonation and subsequent hydration can significantly refine the pore size and improve the density of samples. XRD， TG-DTG， FT-IR， and SEM-EDS reveal that CaCO₃ generated by carbonation interacted with hydration products to form a three-dimensional cross-linked structure， markedly enhancing microstructural compactness and mechanical performance.

Key words: low-heat cement, steel slag, carbonation curing, hydration curing, carbonation depth, compressive strength, microstructure

CLC Number:

TU528

WEN He, ZHANG Xiaoxiang, GU Lei, DENG Jiaxin. Synergistic Carbonation-Hydration Mechanisms and Microstructural Evolution in Low-Heat Cement and Steel Slag Mortars[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(2): 562-572.

Figures/Tables 13

References 39

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Material	Mass fraction/%
Material	CaO	SiO₂	Fe₂O₃	MgO	Al₂O₃	MnO	P₂O₅	TiO₂	Cr₂O₃	Other
Low heat cement	62.43	21.53	4.23	1.08	4.57	3.24	0.68	0.37	0.55	1.32
Steel slag	40.88	13.85	29.26	4.24	2.24	4.49	2.83	1.08	0.44	0.69

Material	Mass fraction/%
Material	CaO	SiO₂	Fe₂O₃	MgO	Al₂O₃	MnO	P₂O₅	TiO₂	Cr₂O₃	Other
Low heat cement	62.43	21.53	4.23	1.08	4.57	3.24	0.68	0.37	0.55	1.32
Steel slag	40.88	13.85	29.26	4.24	2.24	4.49	2.83	1.08	0.44	0.69

Material	Mass fraction/%
Material	C₂S	C₃S	C₃A	C₄AF	Total
Low heat cement	41.80	30.80	2.86	15.00	90.46

Material	Mass fraction/%
Material	C₂S	C₃S	C₃A	C₄AF	Total
Low heat cement	41.80	30.80	2.86	15.00	90.46

Sample No.	Low heatcement mass fraction/%	Steel slagmassfraction/%	Binder-sand ratio （mass ratio）	Water-binder ratio （mass ratio）	Water reducer massfraction/%	CO₂ curingtime/h	Standard curing time/d
A1	100	0	1∶1	0.25	0.5	48	—
A2	50	50	1∶1	0.25	0.5	48	—
B1	100	0	3∶5	0.25	0.8	12， 24， 48	3， 7， 28
B2	75	25	3∶5	0.25	0.8	12， 24， 48	3， 7， 28
B3	50	50	3∶5	0.20	1.2	12， 24， 48	3， 7， 28
B4	50	50	3∶5	0.25	0.8	12， 24， 48	3， 7， 28
B5	50	50	3∶5	0.30	0.1	12， 24， 48	3， 7， 28