ABBE L6 Building Surveying Practice Questions - ABBE CBCS Level 6 Diploma In Building Surveying (ABBE, UK) Exam

Carbon dioxide lowers the pH of the concrete, destroying the protective alkaline passivation layer around the steel reinforcement and leading to rust expansion. Carbon dioxide reacts chemically with steel to dissolve it directly into iron carbonate. Carbonation causes the aggregates to expand, producing map cracking on the surface. Carbonation increases the porosity of the concrete, allowing water to pass through like a sponge.