CONCRETEFiX 6.4 – Using Colloidal Silica to Protect Concrete from Biogenic Sulfuric Acid Attack in Wastewater and Organic Waste Environments
By Brent Rollins, Vice President of Business Development Spray-Lock Concrete Protection, LLC
Concrete structures in sanitary sewage, agricultural, and food processing environments face severe degradation from biogenic sulfuric acid (BSA) corrosion, where bacterial metabolism of waste produces hydrogen sulfide gas (H2S) that oxidizes to sulfuric acid (H2SO4). This acid reacts with cement hydration products, forming expansive gypsum and leading to spalling, cracking, and reduced service life. Colloidal silica, consisting of nano-sized amorphous silicon dioxide (SiO2) in a water-based carrier formula, has been shown to reduce concrete permeability significantly. Reducing permeability is the primary durability strategy for many concrete exposure conditions including in environments where BSA is present.
This presentation reviews the published data regarding colloidal silica’s ability to help protect against BSA, then moves to the field to examine several real-world projects where colloidal silica has been used as part of a protection strategy. While results vary by dosage, application method, and exposure severity, overall evidence supports extended service life and reduced maintenance.
DATE: Thursday, 25 June 2026
via Microsoft Teams @ 15:00
Attendance Free
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RSVP:
Natasja Pols on or before Wednesday, 24 June 2026
natasja.pols@concretesocietysa.org.za