Preparation and Performance of Hydrophobic-Modified Calcined Diatomite Mortar

doi:10.16552/j.cnki.issn1001-1625.2025.0911

Abstract

Abstract:

To enhance the waterproofing and impermeability of cement-based materials， this paper proposed a method for preparing green superhydrophobic powder. Using stearic acid as modifier， calcined diatomite （CD） underwent hydrophobic modification via mechanical ball milling. Process parameters were optimized with contact angle as the primary evaluation metric， successfully yielding modified calcined diatomite （SA-CD） with outstanding hydrophobic properties. The SA-CD was characterized using X-ray diffractometer （XRD）， Fourier transform infrared spectrophotometer （FTIR）， and scanning electron microscopy （SEM）. The effects of substituting cement with SA-CD at different dosages on mortar properties were systematically investigated. Results indicate that under process conditions of 3% （mass fraction） stearic acid dosage， 30 min ball milling time， and 500 r/min rotation speed， the prepared SA-CD shows a contact angle of 152°. As the SA-CD dosage increases， the mortar contact angle continuously rises while the capillary water absorption coefficient significantly decreases， simultaneously exhibiting a flow trend that initially increases before decreasing. At a 6% （mass fraction） SA-CD， the mortar’s 28 d flexural strength and compressive strength improve by 8.81% and 10.44%， respectively. Microscopic analysis indicates that moderate SA-CD dosage improves pore structure and enhances density， thereby strengthening the mortar’s overall performance.

Key words: stearic acid, calcined diatomite, contact angle, capillary water absorption, mechanical property, microstructure

CLC Number:

TU578.1

WANG Haihao, GAN Yuanchu, HOU Qingzhen, CHEN Zhenfu, JIN Dan, FU Xinbo. Preparation and Performance of Hydrophobic-Modified Calcined Diatomite Mortar[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(4): 1122-1131.

Figures/Tables 17

Table 1 Main chemical composition of cement and CD

Material	Mass fraction/%
Material	SiO₂	Al₂O₃	CaO	SO₃	Fe₂O₃	MgO	LOI
Cement	21.56	9.75	49.28	1.04	2.79	1.97	4.41
CD	91.83	2.40	0.53	0.09	1.85	0.93	2.37

Fig.1 Preparation process of SA-CD

Fig.2 Particle size distribution of CD and SA-CD

Table 2 Mix proportion of mortar

Number	Mass/g
Number	Cement	Water	Sand	SA-CD
S0	450.0	202.5	1 350.0	0
S3	436.5	202.5	1 350.0	13.5
S6	423.0	202.5	1 350.0	27.0
S9	409.5	202.5	1 350.0	40.5
S12	396.0	202.5	1 350.0	54.0
S15	382.5	202.5	1 350.0	67.5

Fig.3 Effect of stearic acid dosage on contact angle of SA-CD

Fig.4 Effects of ball milling time and rotational speed on contact angle of SA-CD

Fig.5 XRD patterns of CD and SA-CD

Fig.6 FTIR spectra of CD and SA-CD

Fig.7 SEM images of CD and SA-CD

Fig.8 Effect of SA-CD dosage on mortar wettability

Fig.9 Effect of SA-CD dosage on mortar capillary water absorption rate

Fig.10 Effect of SA-CD dosage on mortar flow

Fig.11 Effect of SA-CD dosage on mortar flexural strength

Fig.12 Effect of SA-CD dosage on mortar compressive strength

Fig.13 Differential distribution of pores within mortar

Fig.14 Distribution of relative values of pore diameters within mortar

Fig.15 Microstructure within mortar

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