What are the risks of using untreated concrete in acidic or saline environments?

Using untreated concrete in acidic or saline environments poses significant risks to structural integrity and longevity. Concrete's alkaline nature makes it particularly vulnerable to chemical attack in these conditions, leading to progressive deterioration that compromises entire structures.

In acidic environments, pH levels below 5.5 initiate chemical reactions that dissolve calcium hydroxide and calcium silicate hydrate - the essential compounds providing concrete's strength and durability. This chemical erosion manifests as surface etching, loss of mass, and increased permeability. The damage accelerates when acidic solutions penetrate deeper layers, eventually reaching the steel reinforcement. The corrosion of rebar then creates internal pressure from rust expansion, causing cracking and spalling that further exposes new concrete surfaces to attack.

Saline environments present equally dangerous threats through multiple mechanisms. Chloride ions from saltwater penetrate concrete pores, depassivating the protective oxide layer on reinforcement steel and initiating corrosion. Sulfate salts react with concrete compounds to form expansive crystalline products that generate internal stresses, leading to cracking and disintegration. The cyclic wetting and drying in coastal areas concentrates salts, accelerating these destructive processes.

The combined effects include reduced structural strength, increased maintenance costs, and shortened service life. Critical infrastructure like marine structures, industrial floors, and wastewater facilities require special protective measures including proper concrete mix design, protective coatings, and corrosion-resistant reinforcements to mitigate these risks. Preventive strategies during construction prove far more effective and economical than attempting to repair damage after it occurs.