In-depth analysis of the long-term waterproofing mechanism of oily grouting fluid

According to the 2023 annual survey report of the China Building Waterproof Association, the average failure period of traditional acrylic grouting materials in basement side wall construction is only 2.3 years, of which 78.6% of re-leakage cases occur in areas with seasonal temperature differences exceeding 25°C. More seriously, in a continuous negative water pressure environment (such as groundwater level fluctuation areas), conventional water-soluble slurry will "re-dissolve", causing the sealing system to collapse.

The molecular-level solution uses an oily formula with an isocyanate (-NCO) content of 28%. Its hydrophobic long-chain structure (molecular weight 4000-6000) achieves permanent sealing through a three-step reaction:

1. Initial penetration stage: low molecular weight prepolymer with a viscosity of only 50mPa·s (25℃) can penetrate into 0.05mm microcracks
2. Expansion and curing stage: after contacting water, the -NCO group reacts to generate CO₂, resulting in a 500% volume expansion rate (ASTM D2202 standard test)
3. Final state stabilization stage: an interpenetrating network structure containing urea bonds is formed, and the tensile strength retention rate is still 85% at -30℃

Shanghai World Financial Center Actual Case Radioactive crack groups were found in the underground three-story parking lot of this project, with a maximum crack width of 1.2mm and continuous seepage. The construction team adopted the "inclined hole grouting + pressure gradient control method":

• Drilling parameters: hole diameter 8mm, inclination 45°, hole depth 30cm, spacing 20cm plum blossom arrangement
• Grouting control: initial pressure 0.3MPa step-up to 0.8MPa, grouting volume 18kg/m
• Material selection: German BASF Masterseal 345 special oily slurry After treatment and 3 freeze-thaw cycle tests, the leakage point was completely eliminated, saving 47 days of construction time compared with the traditional excavation plan.