Hydrophobic hydrogels as internal curing agent for concrete: The double benefit of super high water content and excellent anti-ion permeability

Owing to their high water content, conventional superabsorbent polymer (SAP) hydrogels can serve as internal curing agents for concrete fabrication. However, the hydrophilic network in such hydrogels permits ion diffusion, which induces severe steel corrosion inside concrete in the marine environment. Herein, we introduce a brand-new hydrogel, termed “hydrophobic hydrogels”, for concrete curing. On one hand, these hydrogels possess super high water content (up to 99.6 wt%), which is even higher than that in normal SAP hydrogels; on the other hand, the anhydrous inhomogeneous hydrophobic structures can significantly retard or stop the ion permeation, which is significantly superior to SAP hydrogels. With ion diffusion measurement, the hydrophobic hydrogels achieve much better ion resistance than SAP hydrogels, with 2–5 orders' decrease in ion permeation rate . Among diverse hydrophobic hydrogels, the polymer's hydrophobicity and glass transition directly determine the permeation performance. Hydrogels with a more hydrophobic network and higher polymer T g possess better anti-ion diffusion properties. At the optimal state, the poly(phenyl acrylate) hydrophobic hydrogels can completely stop the permeation process. Owing to the double benefit, the hydrophobic hydrogel cured concretes demonstrate a notable decrease in ion permeation compared to SAP hydrogel cured concrete, with only 1/20 of ion permeation to that in SAP groups with an electric flux test upon coated on the surface layers. Owing to the double benefit from super high water content and excellent anti-ion permeability, these hydrophobic hydrogels may serve as ideal candidates as concrete curing agents in the future. • Hydrophobic hydrogels are applied as internal curing agents for concrete for the first time. • The hydrophobic hydrogels possess super high water content in different aqueous media (max. 99.6 wt%). • The hydrophobic hydrogels achieve much better ion resistance than conventional superabsorbent hydrogels, with up to 5 orders' decrease in ion permeation rate. • Owing to the double benefit, the hydrophobic hydrogels treated concretes manifest noticeably enhanced ion resistance, with 1/20 of ion permeation to that in superabsorbent hydrogel concretes.

由于其高含水量，传统的高吸水性聚合物（SAP）水凝胶可用作混凝土制造的内养护剂。然而，此类水凝胶中的亲水网络会允许离子扩散，这在海洋环境中会导致混凝土内部的严重钢筋腐蚀。在此，我们引入一种全新的水凝胶，称为“疏水水凝胶”，用于混凝土养护。一方面，这些水凝胶具有超高的含水量（高达99.6 wt%），甚至比普通SAP水凝胶的含水量还高；另一方面，无水的非均相疏水结构能够显著延缓或阻止离子渗透，这明显优于SAP水凝胶。通过离子扩散测量，疏水水凝胶比SAP水凝胶具有更好的抗离子性能，离子渗透率降低2 - 5个数量级。在不同的疏水水凝胶中，聚合物的疏水性和玻璃化转变直接决定渗透性能。具有更疏水网络和更高聚合物Tg的水凝胶具有更好的抗离子扩散性能。在最佳状态下，聚丙烯酸苯酯疏水水凝胶能够完全阻止渗透过程。由于双重优势，与SAP水凝胶养护的混凝土相比，疏水水凝胶养护的混凝土离子渗透率显著降低，在表面涂层后进行电通量测试时，其离子渗透率仅为SAP组的1/20。由于超高含水量和优异的抗离子渗透性的双重优势，这些疏水水凝胶未来可能成为混凝土养护剂的理想选择。 • 疏水水凝胶首次被用作混凝土的内养护剂。 • 疏水水凝胶在不同的水性介质中具有超高含水量（最高99.6 wt%）。 • 疏水水凝胶比传统的高吸水性水凝胶具有更好的抗离子性能，离子渗透率降低多达5个数量级。 • 由于双重优势，经疏水水凝胶处理的混凝土表现出明显增强的抗离子性能，其离子渗透率是高吸水性水凝胶混凝土的1/20。