Hydrophobic Properties and Mechanism of TEOS-IBT Synergistically Modified Cement Paste

doi:10.16552/j.cnki.issn1001-1625.2025.1160

Abstract

Abstract:

To improve the hydrophobic properties of cement-based materials， isobutyl triethoxysilane （IBT） and tetraethyl orthosilicate （TEOS） were used to singly and jointly modify P·I 52.5 Portland cement paste （water-cement ratio of 0.35）. The content of IBT or TEOS was set to 1%~6% （mass fraction）， and 1%~3% TEOS was compounded on the basis of fixing the IBT content at 3% （mass fraction）. The cement paste was characterized by tests of fluidity， setting time， compressive strength， contact angle， capillary water absorption coefficient （S）， heat of hydration， combined with characterization techniques such as SEM、FTIR and XRD. The results show that the co-admixture markedly amplifies surface hydrophobicity， the compound addition of IBT-3%+TEOS-3% increases the contact angle up to 140.0°， compared with the single addition of 3% IBT， the contact angle is increased by 58.37%. In terms of moisture transport performance， IBT-4% reduces capillary water absorption coefficient （S） from the control value of 0.004 19 mm·s^-1/2 to 0.000 99 mm·s^-1/2； When TEOS of 1%~3% is compounded on the basis of fixing the IBT content at 3%， S is 0.002 93~0.003 63 mm·s^-1/2， higher than IBT-3% alone group but still 13%~30% lower than the control. Based on the above results， this study reveals the synergistic mechanism of TEOS and internally mixed IBT in modified cement paste， and provides an operable basis for the design of hydrophobic cement-based materials.

Key words: cement-based material, isobutyl triethoxysilane, tetraethyl orthosilicate, hydrophobicity, modification

CLC Number:

TU528.042

CHENG Zigao, CONG Yun, ZHANG Yan, LI Gen, ZHI Tianyi, TAN Hongbo. Hydrophobic Properties and Mechanism of TEOS-IBT Synergistically Modified Cement Paste[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(6): 1903-1913.

Figures/Tables 16

Table 1 Main chemical composition of Portland cement

Chemical composition	CaO	SiO₂	Al₂O₃	MgO	Fe₂O₃	SO₃	Other
Mass fraction/%	58.884	22.885	7.181	3.361	2.919	2.162	0.897

Fig.1 XRD pattern of Portland cement

Fig.2 Schematic diagram of chemical structures of raw materials

Table 2 Mix ratio of cement paste test blocks

Sample	Mass/g
Sample	Cement	Water	IBT	TEOS
Control	300	105	0	0
IBT-1%	300	105	3	0
IBT-2%	300	105	6	0
IBT-3%	300	105	9	0
IBT-4%	300	105	12	0
IBT-5%	300	105	15	0
IBT-6%	300	105	18	0
TEOS-1%	300	105	0	3
TEOS-2%	300	105	0	6
TEOS-3%	300	105	0	9
TEOS-4%	300	105	0	12
TEOS-5%	300	105	0	15
TEOS-6%	300	105	0	18
IBT-3%+TEOS-1%	300	105	9	3
IBT-3%+TEOS-2%	300	105	9	6
IBT-3%+TEOS-3%	300	105	9	9

Fig.3 Preparation flow chart of cement paste

Fig.4 Effect of hydrophobic agent on fluidity of cement paste

Fig.5 Effect of hydrophobic agent on setting time of cement paste

Fig.6 Effect of hydrophobic agent on compressive strength of cement paste

Fig.7 Effect of hydrophobic agent on contact angle of cement paste

Fig.8 Hydrophobic mechanism diagram

Fig.9 Effect of hydrophobic agent on capillary water absorption of cement paste

Fig.10 Capillary water absorption coefficient of cement paste in each system

Fig.11 Effect of hydrophobic agent on hydration heat of cement paste

Fig.12 SEM images of cement paste

Fig.13 FTIR of cement pastes

Fig.14 XRD patterns of cement pastes

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