Carbonic Anhydrase as a Sustainable Sealing Agent for Concrete Exposed to Chloride Attack

Concrete, the most used engineering material in the world, is responsible for 8% of the entire CO₂ emission; 80% of the failures in reinforced concrete structures are related to the corrosion of embedded reinforcement. Concrete resistivity against chloride penetration is a pivotal parameter in determining the durability of reinforced concrete structures. Self-sealing concrete has recently emerged as a powerful method for enhancing this resistance. This paper investigates the effect of carbonic anhydrase (CA) as a sealing agent on the chloride penetration of concrete by the rapid chloride penetration test (RCPT). Concrete disk specimens without CA and with two different dosages of CA were cast and cured for 14 and 28 days. Chloride penetration depths and migration coefficients were evaluated for uncracked specimens at 14 and 28 days. The lower dosage of CA was used to prepare cracked and sealed specimens. The chloride content was quantified, and service life was predicted for specimens at 28 days. In uncracked concrete, a lower dosage of CA can considerably increase concrete resistivity to chloride penetration up to 46% compared to the control specimens. Although the presence of a crack increased chloride penetration through the crack, sealing the crack showed penetration depth at the crack zone similar to the uncracked concrete. Hence, using CA enzyme as a sealing agent extends the service life of uncracked concrete and recovers the cracked concrete's service life after sealing. Thus, the addition of enzymes will have significant implications for infrastructure sustainability and reduction of CO₂ emissions related to the second industrial emitter.