Concrete is probably the oldest known construction material in the history of civil engineering. Greeks and Egyptians used lime-based concrete in 2000 BC. In the 17th Century, steel-reinforced concrete was developed following the invention of prestressed concrete in 1928. Throughout the history, researchers and corrosion experts have struggled to develop a concrete reinforcement material that could provide a defensive mechanism against corrosion. In this blog post, I will discuss some of the conditions that seriously damage the strength and life of a reinforced concrete.
1. Aggregate expansion
Aggregates experience chemical reactions in concrete which leads to concrete deterioration. When water freezes, the excessive water absorption makes it difficult for aggregates to accommodate hydraulic pressure and expansion. The process leads to concrete disintegration. Concrete can be restored to its normal strength if it has been frozen at an early age. However, frozen concrete does not remain as effective against weather as the concrete which had not been frozen.
D-cracking is one the types of concrete deterioration caused by aggregate expansion. It is often observed in pavements because of the natural accumulation of water. Concrete can be made effective against weather conditions by selecting aggregates that perform better under severe weather conditions.
The exposure to chemical environments can degrade even the superior quality concrete. Sulfuric acid, aluminum chloride, and hydrochloric acid are few of the chemicals that accelerate concrete deterioration. Groundwater and soil contain sodium, magnesium, calcium and other chemicals. When these chemicals react with hydrated compounds in concrete, the process badly affects the strength and durability of concrete. Carbonatation-initiated deterioration of concrete is an example of the chemical attack. Chemical attacks can be avoided by reinforcing concrete with bars that are resistant against environmental conditions. Marine structures are more vulnerable to corrosion as they have to withstand the most severe environmental conditions.
Erosion refers to a condition where concrete surface is damaged by friction. As the outer layer of concrete wears, it facilitates the degradation process by exposing the coarse aggregate. Roads and hydraulic structures experience the worst form of erosion. The use of studded snow tires, for instance, damage the outer surface of roads. In dams, spillways, and other hydraulic structures, the waterborne elements lead to abrasion damage.
Concrete can be damaged by fire. High temperature affects modulus of elasticity, flexural and compressive strength of concrete. Temperature over 300 Celsius grades is considered to be unhealthy for concrete. A rapid exposure to very high temperature can create steam inside concrete that leads to explosive spalling.
There are several factors that can cause concrete degradation. However, high-quality reinforcement material can protect concrete structures from corrosive agents, radiation, heat, weather, and physical damages. Fiberglass rebar is an emerging construction solution which deals exceptionally well with severe environmental conditions, enabling concrete structures to withstand corrosive agents, heat, radiation, friction, and other dangerous phenomena for more than 100 years.