Influence of active crack width control on the chloride penetration resistance and global warming potential of slabs made with fly ash + silica fume concrete

• Uncracked fly ash + silica fume concrete is very resistant to chloride penetration.
• Uncracked fly ash + silica fume concrete has a long service life (>100 years).
• The seemingly uncracked condition only exists for crack widths below 0.1 mm.
• Limiting the maximum crack width allowed requires more reinforcing steel in concrete slabs.
• More reinforcing steel results in a substantial increase of the slab’s global warming potential.

Service life predictions for concrete exposed to chloride-induced corrosion usually result from durability tests performed on uncracked concrete. Chloride migration coefficients for uncracked concrete should only be used if the structure can be considered as uncracked. The seemingly uncracked condition requires crack widths below 0.1 mm. The extra reinforcing steel to achieve this in concrete slabs, results in a 30–43% increase of the global warming potential. Fly ash + silica fume concrete may be preferred because of its low 28 day migration coefficient (3.4 × 10−12 m2/s), its long service life (>100 years) and its autogenous healing ability.