Hydration Properties of Polyvinyl Alcohol-Modified Slag-Fly Ash-Based Alkali-Activated Cementitious Materials

doi:10.16552/j.cnki.issn1001-1625.2025.1009

Abstract

Abstract:

Although alkali-activated cementitious materials exhibit lower greenhouse gas emissions and mechanical properties comparable to those of Portland cement， they suffer from problems such as significant drying shrinkage， susceptibility to cracking， and notable performance fluctuations. Incorporating polyvinyl alcohol （PVA） can effectively reduce drying shrinkage， enhance flexural strength and toughness， and promote structural densification. This study systematically investigated the effects of different PVA content （0%， 2.5%， 5.0%， 7.5%， and 10.0%， mass fraction） on the fluidity， setting time， hydration heat， compressive strength， flexural strength， drying shrinkage， mass loss， pH value， water absorption rate， and microstructure of slag-fly ash-based alkali-activated cementitious materials. The results show that as the PVA content increases， the paste fluidity decreases and the final setting time is prolonged； both the hydration heat release rate and cumulative heat release decrease； the compressive strength decreases with higher PVA content， whereas the flexural strength improves after 28 d of curing， with the highest flexural strength （6.63 MPa） achieved at a PVA content of 5.0%； drying shrinkage is reduced when the PVA content does not exceed 5.0%， but increases when the content exceeds 5.0%； the introduction of PVA also leads to a decrease in paste pH value and an increase in water absorption rate. Microstructural analysis indicates that PVA films and hydration products mutually encapsulate and fill each other， forming a composite structure that enhances the microscopic densification of the material. This study clarifies the regulatory effect of PVA on the hydration behavior and macroscopic properties of alkali-activated cementitious materials， providing a basis for their engineering applications.

Key words: polyvinyl alcohol, alkali-activated cementitious material, hydration property, drying shrinkage, flexural strength, microstructure

CLC Number:

TQ177

LI Binghan, LI Shiji, ZHAO Yimeng, LIU Yunpeng, XU Da, ZHAO Shuli. Hydration Properties of Polyvinyl Alcohol-Modified Slag-Fly Ash-Based Alkali-Activated Cementitious Materials[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(5): 1638-1649.

Figures/Tables 19

Table 1 Main chemical composition of slag and fly ash

Material	Mass fraction/%
Material	SiO₂	Al₂O₃	Fe₂O₃	CaO	TiO₂	K₂O	SO₃	MgO	P₂O₃	Na₂O
Slag	29.43	14.38	0.90	44.50	1.61	0.35	2.34	5.49	0.03	0.28
Fly ash	48.70	35.90	5.06	3.88	0.70	1.36	0.80	0.61	0.50	0.38

Table 2 Performance indexes of PVA

Test item

Methylation degree

（mass fraction）/%

Viscosity/（MPa·s）

Volatile matter

（mass fraction）/%

Purity（mass fraction）/%

Table 3 Mix proportion of PVA-modified slag-fly ash-based alkali-activated cementitious materials

Group	Mass/g				Water-binder ratio
Group	Slag	Fly ash	PVA	Na₂O	Water-binder ratio
PVA0	80	20	0	3	0.4
PVA1	80	20	2.5	3	0.4
PVA2	80	20	5.0	3	0.4
PVA3	80	20	7.5	3	0.4
PVA4	80	20	10.0	3	0.4

Fig.1 Fluidity of PVA-modified slag-fly ash-based alkali-activated composite paste

Fig.2 Setting time of PVA-modified slag-fly ash-based alkali-activated composite paste

Fig.3 Effect of PVA content on hydration heat release rate of PVA-modified alkali-activated cementitious materials

Fig.4 Effect of PVA content on hydration heat release of PVA-modified alkali-activated cementitious materials

Fig.5 Development law of compressive strength of neat paste specimens over time

Table 4 Relative compressive strength and relative flexural strength

Age/d	Sample	CON（strength）	2.5%PVA	5.0%PVA	7.5%PVA	10.0%PVA
3	Compressive strength	1	0.836	0.731	0.485	0.289
3	Flexural strength	1	0.626	0.602	0.579	0.390
7	Compressive strength	1	0.911	0.826	0.604	0.398
7	Flexural strength	1	0.583	0.581	0.604	0.352
14	Compressive strength	1	0.860	0.738	0.635	0.495
14	Flexural strength	1	0.964	1.111	1.054	0.697
28	Compressive strength	1	0.890	0.844	0.686	0.533
28	Flexural strength	1	1.139	1.295	1.230	1.049

Fig.6 Effect of PVA content on drying shrinkage of slag-fly ash-based alkali-activated paste

Fig.7 Effect of PVA content on mass loss of slag-fly ash-based alkali-activated paste

Fig.8 Effect of PVA content on pH value of slag-fly ash-based alkali-activated paste

Table 5 OH- content of PVA1 and PVA4

Item	Sample mass/g	c（HCL）/（mol·L^-1）	V₀（Blank）/mL	V₁（EP1）/mL	OH^- content/（mg·g^-1）	Average OH^- content/（mg·g^-1）
PVA1-1	0.512 4	0.1	0.009 5	2.043 2	6.750	6.773
PVA1-2	0.515 4	0.1	0.009 5	2.069 3	6.797	6.773
PVA4-1	0.511 2	0.1	0.009 5	1.044 6	3.444	3.425
PVA4-2	0.499 2	0.1	0.009 5	1.009 2	3.406	3.425

Fig.9 Water absorption rate varies with PVA content

Fig.10 XRD patterns of 0%， 2.5%， and 10.0% with PVA content

Fig.11 SEM images with 0% PVA content

Fig.12 SEM images with 2.5% PVA content

Fig.13 SEM images with 10.0% PVA content

Fig.14 FTIR spectra with PVA content of 0%， 2.5%， and 10.0%

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