Influence of crystalline admixtures on the durability of uncracked concrete in chloride environments

The service life of reinforced concrete structures in chloride environments can be impacted by reinforcement corrosion. In coastal environments, chloride ions can lead to local de-passivation of the steel rebars by diffusing through concrete pores. Although crystalline admixture (CA) has recently garnered attention due to its ability to self-heal concrete cracks, its potential to limit reinforcement corrosion in uncracked concrete is poorly understood. This study is focused explicitly on uncracked concrete, where self-healing is minimal. It investigates the performance of uncracked mortar and concrete samples containing 0.5 %, 1 %, or 1.5 % CA compared to reference specimens without CA. At this dosage, no new solid phase from the addition was observed, but the Thermogravimetric analysis (TGA) results of pure hydrated CA powder hinted at an increase in calcite formation. No remarkable effect of CA is noted in the mechanical and transport properties of concrete, with marginal evidence of limiting steel corrosion. The greater sodium content identified in the pore solution of CA mixes leads to a double-edged effect of higher heat release in hydration, which resulted in higher early strength, but also increased chloride ingress. However, corrosion experiments showed that when used properly, CA has the potential to limit reinforcement corrosion even in uncracked concrete. • Crystalline admixture (CA) affects early hydration, increases heat release. • High sodium concentration in pore solution from CA reduces electrical resistivity. • High sodium concentration in pore solution accelerates chloride diffusion. • Sodium carbonate in CA powder accelerates carbonation to create calcite crystals. • CA addition only marginally limits the extent of chloride-induced rebar corrosion.