Synthesis of Hyperbranched Admixture and Its Effect on Low Water-Cement Ratio Cement Paste

doi:10.16552/j.cnki.issn1001-1625.2026.0289

Abstract

Abstract:

In order to regulate the rheological properties of ultra-high performance concrete effectively， an admixture with hyperbranched topological structure was synthesized by pentaerythritol， acrylic acid， methyl acryloxy polyoxyethylene ether （HPEG） and ceric ammonium nitrate （CAN）. The effects of the types and molecular weights of the monomers， the ratio of pentaerythritol to the monomers， and the initiator system on the fluidity and viscosity of the cement paste were investigated. The results show that when the monomer used is HPEG with a molecular weight of 1 000 g/mol， the ratio of pentaerythritol to the monomer is 0.012 5∶1， and the initiator used is ammonium cerium nitrate，the synthesized hyperbranched admixture combined with the laboratory-synthesized comb-like polycarboxylic water-reducing admixture at dosages of 0.3%（mass fraction） and 0.7%（mass fraction） respectively， is added to the cement paste with a water-cement ratio of 0.18， the flowability is 200 mm and the viscosity is 1 637 mPa·s. The viscosity is 31.8% lower than that of the commercially available UHPC admixture， achieving optimal rheological properties. Microscopic characterization methods， such as gel permeation chromatography， Fourier transform infrared spectroscopy， hydrodynamic radius， Zeta potential， total organic carbon and rheological property tests， were used to analyze the mechanism. The results show that the hyperbranched topological structure admixture has a compact molecular structure， a rich distribution of terminal functional groups， a fast interfacial adsorption rate， and also exhibits excellent dispersion and viscosity reduction properties.

Key words: hyperbranched admixture, molecular design, low water-cement ratio, rheological property, interface adsorption, viscosity reduction property

CLC Number:

TU528

MAO Zhiyi, ZHU Yizhou, YANG Renhe, QIE Feifan, ZHANG Pengyu, SUN Qian, LIU Xiao. Synthesis of Hyperbranched Admixture and Its Effect on Low Water-Cement Ratio Cement Paste[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(9): 3126-3139.

Figures/Tables 14

Table 1 Chemical composition of cement

Composition	SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	SO₃	Na₂Oeq	f-CaO	LOI
Mass fraction/%	20.82	4.97	3.81	63.17	3.87	0.40	0.60	0.89	1.47

Fig.1 Synthesis mechanism of hyperbranched topological structure by free radical initiation of ammonium cerium nitrate polymerization

Table 2 Raw material ratio of different hyperbranched polymers

Sample No.	Core		Macromonomer		Micro-monomer	Initiator		Chain transfer agent
E-1	Name	Pentaerythritol	EPEG-1200	EPEG-3000	AA	CAN		MPA
E-1	Molar ratio	0.012 5	1.00	0	2.78	0.1		0.045
E-2	Name	Pentaerythritol	EPEG-1200	EPEG-3000	AA	CAN		MPA
E-2	Molar ratio	0.012 5	0.75	0.25	2.78	0.1		0.045
E-3	Name	Pentaerythritol	EPEG-1200	EPEG-3000	AA	CAN		MPA
E-3	Molar ratio	0.012 5	0.50	0.50	2.78	0.1		0.045
E-4	Name	Pentaerythritol	EPEG-1200	EPEG-3000	AA	CAN		MPA
E-4	Molar ratio	0.012 5	0.25	0.75	2.78	0.1		0.045
E-5	Name	Pentaerythritol	EPEG-1200	EPEG-3000	AA	CAN		MPA
E-5	Molar ratio	0.012 5	0	1.00	2.78	0.1		0.045
JS-1	Name	PT	EPEG-1200		AA	H₂O₂	E51	MPA
JS-1	Molar ratio	0.006 25	1.00		2.78	0.19	0.02	0.045
JS-2	Name	PT	EPEG-1200		AA	H₂O₂	E51	MPA
JS-2	Molar ratio	0.012 5	1.00		2.78	0.19	0.02	0.045
JS-3	Name	PT	EPEG-1200		AA	H₂O₂	E51	MPA
JS-3	Molar ratio	0.025	1.00		2.78	0.19	0.02	0.045
JS-4	Name	PT	EPEG-1200		AA	H₂O₂	E51	MPA
JS-4	Molar ratio	0.05	1.00		2.78	0.19	0.02	0.045
JS-5	Name	PT	EPEG-1200		AA	H₂O₂	E51	MPA
JS-5	Molar ratio	0.1	1.00		2.78	0.19	0.02	0.045
H-1	Name	Pentaerythritol	HPEG-1000		AA	CAN		MPA
H-1	Molar ratio	0.012 5	1.00		2.78	0.1		0.045
H-2	Name	Pentaerythritol	HPEG-1000		AA	CAN		MPA
H-2	Molar ratio	0.05	1.00		2.78	0.1		0.045
H-3	Name	Pentaerythritol	HPEG-1000		AA	CAN		MPA
H-3	Molar ratio	0.012 5	1.00		2.78	0.1		0.09
H-4	Name	Pentaerythritol	HPEG-1000		AA	CAN		TGA
H-4	Molar ratio	0.012 5	1.00		2.78	0.1		0.045
H-5	Name	Pentaerythritol	HPEG-1000		AA	CAN		TGA
H-5	Molar ratio	0.012 5	1.00		2.78	0.1		0.09
H-ZH	Name	Esterification core	HPEG-1000		AA	APS		MPA
H-ZH	Molar ratio	0.012 5	1.00		2.78	0.28		0.045

Table 3 Viscosity reduction effect of hyperbranched polymers systhesized by combination of EPEG with different molecular weights

Sample No.	Content	Fluidity/mm	1 h fluidity/mm	Viscosity/（mPa·s）	Relativity/%
C	1%（mass fraction）	200	170	2 013	—
E-1	0.7%C+0.3%H （mass fraction）	180	165	3 637	+80.7
E-2		190	160	2 537	+26.0
E-3		195	160	2 632	+30.8
E-4		195	160	2 463	+22.4
E-5		190	160	2 558	+27.1

Table 4 Viscosity reduction effect of hyperbranched polymers synthesized from pentaerythritol triacrylate with different dosages

Sample No.	Content	Fluidity/mm	1 h fluidity/mm	Viscosity/（mPa·s）	Relativity/%
C	1%（mass fraction）	200	170	2 013	—
JS-1	0.7%C+0.3%H （mass fraction）	190	160	2 707	+34.5
JS-2		195	160	2 537	+26.0
JS-3		195	165	2 560	+27.2
JS-4		180	150	3 546	+76.1
JS-5		180	160	3 966	+97.0

Table 5 Viscosity reduction effect of hyperbranched polymers synthesized with different parameters in HPEG system

Sample No.	Content	Fluidity/mm	1 h fluidity/mm	Viscosity/（mPa·s）	Relativity/%
C	1%（mass fraction）	200	170	2 013	—
H-1	0.7%C+0.3%H （mass fraction）	200	180	1 637	-18.67
H-2		195	170	1 825	-9.33
H-3		195	170	2 244	+11.47
H-4		180	155	3 950	+96.22
H-5		190	165	3 116	+54.79
H-ZH		195	165	2 140	+6.31

Fig.2 GPC spectrum of sample H-1

Fig.3 FTIR spectra of two different structural admixtures moleculars

Fig.4 Hydrodynamic radius distribution in pore solution simulated by different structural admixtures

Table 6 Results of variation of Zeta potential on surface of cement particles with time

Admixture	Zeta potential/mV
Admixture	0 min	30 min	60 min	90 min
Blank	-0.10	3.67	4.03	4.56
CKA-50	-0.93	3.86	3.97	4.32
H-1	-1.22	3.44	3.89	4.01

Fig.5 Variation of Zeta potential on surface of cement particles with time

Fig.6 Adsorption behavior of cement particles by admixtures with different structures

Fig.7 Results of M-B model fitting

Table 7 Results of M-B model fitting

Sample	Fitting equation	τ₀/Pa	η_P/（Pa·s）	R²
CKA-50	τ=30.041 3+2.317 9 $γ ˙$ +4.786 1×10^-4 $γ ˙$ ²	30.041 3	2.317 9	0.998
H-1	τ=25.569 8+1.884 5 $γ ˙$ +6.374 2×10^-4 $γ ˙$ ²	25.569 8	1.884 5	0.998

Table 7 Results of M-B model fitting

Sample	Fitting equation	τ₀/Pa	η_P/（Pa·s）	R²
CKA-50	τ=30.041 3+2.317 9 $γ ˙$ +4.786 1×10^-4 $γ ˙$ ²	30.041 3	2.317 9	0.998
H-1	τ=25.569 8+1.884 5 $γ ˙$ +6.374 2×10^-4 $γ ˙$ ²	25.569 8	1.884 5	0.998

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