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<p>In this paper, the effect of the sol–gel network structure generated by the reaction of a novel composite hydroxyl-capped polydimethylsiloxane (HPDMS), tetraethoxysilane(TEOS), 3-(isobutyryloxy) propyltrimethoxysilane(KH-570), and poly(methylhydrogen siloxane) (PMHS) on the hydrophobic performance of hemihydrous phosphogypsum (HPG) was investigated. The prepared composite hydrophobic agent (abbreviated as TH hydrophobic agent) was mixed with HPG slurry to explore the effect on the hydrophobic properties of HPG and to analyze the hydrophobic mechanism of its sol–gel network structure. Results showed that the TH hydrophobic agent improved HPG hydrophobicity, with the optimal 9% dosage yielding a maximum contact angle of 126.17°, a water absorption of 1.11%, a softening coefficient of 0.96, dry and water-saturated compressive strengths of 30.35&#xa0;MPa and 29.25&#xa0;MPa, an 89.8% reduction in water absorption and an 18.8% increase in softening coefficient compared to the blank sample. Compared with the blank sample, the water absorption decreased by 89.8%, the softening coefficient increased by 18.2%, and the dry compressive strength and water-saturated compressive strength increased by 11% and 215%, respectively. TEOS, KH-570, HPDMS, and PMHS can exert synergistic effects on HPG to further improve the hydrophobic properties of HPG.Compared with the modification efficacy of conventional silane-based hydrophobic modifiers for phosphogypsum, the composite sol–gel hydrophobic system fabricated in this study enables the reduction of phosphogypsum’s water absorption to 1.11% and the elevation of its contact angle to 126.17°. Notably, it achieves the synchronous enhancement of both dry and water-saturated compressive strengths, thus overcoming the technical bottleneck that traditional hydrophobic modifiers tend to impair the mechanical properties of phosphogypsum. Combined with the microscopic morphology analysis of the HPG samples, the appropriate proportion of TH hydrophobes filled the pores of the crystals, reduced the porosity, and changed the structure and morphology of the HPG crystals to some extent. The sol–gel network structure can chemically bond with the silanol groups in HPG from the inside out. Moreover, the sol–gel network structure chemically bonds with HPG’s silanol groups from the inside out and contains abundant methyl groups. These groups fully cover the hydroxyl groups on the HPG surface, block water molecule penetration, and thus turn phosphogypsum-based composites from hydrophilic to hydrophobic.</p>

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Effect of a novel sol–gel network based on hydroxyl-capped polydimethylsiloxane and polymethylhydrosiloxane on the hydrophobicity of phosphogypsum-based building materials

  • 期刊论文

  • 发表日期：

    2026年4月3日

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  • Yi Li,
  • Yuanxia Li,
  • Linjun Han,
  • Qibin Liu

摘要

In this paper, the effect of the sol–gel network structure generated by the reaction of a novel composite hydroxyl-capped polydimethylsiloxane (HPDMS), tetraethoxysilane(TEOS), 3-(isobutyryloxy) propyltrimethoxysilane(KH-570), and poly(methylhydrogen siloxane) (PMHS) on the hydrophobic performance of hemihydrous phosphogypsum (HPG) was investigated. The prepared composite hydrophobic agent (abbreviated as TH hydrophobic agent) was mixed with HPG slurry to explore the effect on the hydrophobic properties of HPG and to analyze the hydrophobic mechanism of its sol–gel network structure. Results showed that the TH hydrophobic agent improved HPG hydrophobicity, with the optimal 9% dosage yielding a maximum contact angle of 126.17°, a water absorption of 1.11%, a softening coefficient of 0.96, dry and water-saturated compressive strengths of 30.35 MPa and 29.25 MPa, an 89.8% reduction in water absorption and an 18.8% increase in softening coefficient compared to the blank sample. Compared with the blank sample, the water absorption decreased by 89.8%, the softening coefficient increased by 18.2%, and the dry compressive strength and water-saturated compressive strength increased by 11% and 215%, respectively. TEOS, KH-570, HPDMS, and PMHS can exert synergistic effects on HPG to further improve the hydrophobic properties of HPG.Compared with the modification efficacy of conventional silane-based hydrophobic modifiers for phosphogypsum, the composite sol–gel hydrophobic system fabricated in this study enables the reduction of phosphogypsum’s water absorption to 1.11% and the elevation of its contact angle to 126.17°. Notably, it achieves the synchronous enhancement of both dry and water-saturated compressive strengths, thus overcoming the technical bottleneck that traditional hydrophobic modifiers tend to impair the mechanical properties of phosphogypsum. Combined with the microscopic morphology analysis of the HPG samples, the appropriate proportion of TH hydrophobes filled the pores of the crystals, reduced the porosity, and changed the structure and morphology of the HPG crystals to some extent. The sol–gel network structure can chemically bond with the silanol groups in HPG from the inside out. Moreover, the sol–gel network structure chemically bonds with HPG’s silanol groups from the inside out and contains abundant methyl groups. These groups fully cover the hydroxyl groups on the HPG surface, block water molecule penetration, and thus turn phosphogypsum-based composites from hydrophilic to hydrophobic.