Potassium methyl silicate (CH5SiO3Na) assisted activation and modification of alkali-activated-slag-based drying powder coating for protecting cement concrete. (4th April 2022)

• Record Type: Journal Article
• Authors: Lv, Xue-sen; Qin, Yao; Liang, Hang; Han, Yao-cong; Li, Jing; He, Yan; Cui, Xue-min
• Is Part Of: Construction & building materials. Volume 326(2022)
• Publication Date: 2022-04-04
• Subjects: Geopolymer coating -- Alkali-activated slag -- Waterproof coating -- Corrosion -- Concrete protection -- Chloride; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2022.126858
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: A drying powder coating for concrete protection was fabricated by PMS modifying AAS. PMS had an assisted alkali-activated and hydrophobic-modification effect. The modifying mechanism was studied correlated with alkali-activated reaction. The effect of PMS on the physical-chemical properties of AAS was investigated. The protection mechanism of coating of reinforced concrete was discussed. Abstract: Alkali-activated materials (AAMs) have attracted extension attention as a promising material for protective coating, while its protective efficiency was limited due to inherent poor anti-permeability when subjected to aggressive marine environments. In this work, a novel strategy for hydrophobic modification of alkali-activated slag (AAS) by compositing potassium methyl silicate (PMS) to produce a protective coating for reinforced concrete was reported. Results show that PMS had an assisted-alkali activation, and could graft hydrophobic groups (–CH3 ) on the C-A-S-H/C-S-H gel chemical structure by condensation reaction. While PMS had a retard effect and reduced mechanical property due to the decreased binding energy of atoms and condensation degree of gel. The coating with 5 wt% PMS obtained a compacted microstructure, where gel production increased 26 %, porosity decreased 54 %, and harmless pore volume improved 14 %. The fabricated coating had excellent protective properties, which showed a bonding strength of 1.60 MPa, water contact angle of 128°, water absorption of 2.8 %, chloride ion penetration coefficient of 5.453 × 10 -12 m −2 /s, and the corrosion rate of reinforced rebar decreased by 97 %.