How does carbonation affect durability of concrete?

The carbonation makes the plain concrete more durable because it makes the concrete totally dense, decreases the whole porosity, increases the sulphate resistance and alkali aggregate resistance but in reinforced concrete the value of pH will fall from 13.5 to 8.3 due to this reason the steel losses its passivity which …

What affects the rate of carbonation in concrete?

Factors affecting Concrete Carbonation The rate of carbonation depends on porosity (for CO2to Diffuse) & moisture content of the concrete (for dissolution of solid Ca(OH)2). Relative humidity (for dissolution of Ca(OH)2), The concentration of CO2. Optimal conditions for carbonation occur at a RH of 50\% (range 40–90\%).

What is the result of carbonation?

3 Carbonation. Carbonation is the process of formation of calcium carbonate through reaction of carbon dioxide with concrete constituents of calcium hydroxide, aluminates, and silicates. This process results in the initiation of rebar corrosion in the reinforced concrete (Limbachiya et al., 2012).

What are the typical characteristic of carbonation of concrete?

In moist environments, carbon dioxide present in the air forms an acid aqueous solution that can react with the hydrated cement paste and tends to neutralize the alkalinity of concrete (this process is known as carbonation).

How does carbonation cause concrete cracking?

Concrete carbonation causes embedded steel reinforcements to corrode, with the resulting expansion cracking and weakening the concrete. Rust (Iron oxide) has up to 6 times larger volume than the original steel, so as the steel reinforcements rust, the expansion causes the concrete to crack and spall.

How can you tell if concrete is carbonated?

Carbonation of the concrete, caused by carbon dioxide in the atmosphere, has the effect of reducing the pH. Carbonation depth is assessed using a solution of phenolphthalein indicator that appears pink in contact with alkaline concrete with pH values in excess of 9 and colourless at lower levels of pH.

What causes carbonation of concrete?

Carbonation begins at the concrete surface and slowly penetrates deeper, typically at a rate of about . The carbon dioxide emitted by the heaters reacts with calcium hydroxide on the concrete’s surface and ultimately produces the chalky calcium carbonate coating.

How does carbonation occur in concrete?

Carbonation of concrete is the chemical reaction between carbon dioxide in the air and calcium hydroxide and hydrated calcium silicate in the concrete to give mainly carbonates. Carbonation occurs from the CO 2 exposed surfaces of the concrete structures into the concrete as shown in the figure below.

How does carbonation affect pH of concrete?

Carbonation is the reaction of carbon dioxide in the environment with the calcium hydroxide in the cement paste. This reaction produces calcium carbonate and lowers the pH to around 9. At this value the protective oxide layer surrounding the reinforcing steel breaks down and corrosion becomes possible.

What is the purpose of carbonation test?

Carbonation testing provides a means with which the inspector can determine the extent of carbon dioxide infiltration into the concrete. The process is similar to chloride ion testing where a sample is either removed, either by coring or drilling and the sample is tested by the application of a revealer.

What is carbonation corrosion?

Abstract. In addition to chloride induced corrosion, the other commonly occurring type of rebar corrosion in reinforced concrete structures is that induced by the ingress of atmospheric carbon dioxide into concrete, commonly referred to as ‘carbonation induced corrosion’.

How can you reduce carbonation?

Carbonation can also be reduced by low water/cement ratio[1]. Low water/cement ratio and high strength concrete are possible by Self Compacting Concrete (SCC) where effect of carbonation is less comparatively. The carbonation is found to have tremendous impact on some of the engineering properties of concrete.

What are the effects of carbonation of concrete?

Carbonation of concrete is associated with the corrosion of steel reinforcement and with shrinkage . However, it also increases both the compressive and tensile strength of concrete, so not all of its effects on concrete are bad.

Why does concrete produce CO2?

A single industry accounts for around 5 percent of global carbon dioxide (CO2) emissions. It produces a material so ubiquitous it is nearly invisible: cement. It is the primary ingredient in concrete, which in turn forms the foundations and structures of the buildings we live and work in, and the roads and bridges we drive on.

What are the effects of carbonation?

Carbonation can occur naturally in spring water that picks up carbon dioxide stored in rocks, or it can be forced in by the manufacturer. Claims have been made that carbonated water erodes teeth and bones, leaches calcium and increases acidity in the stomach. These claims have not been borne out by experiment.

What is the process of carbonation?

Carbonation is the process in which carbon dioxide is suspended in water because small air bubbles are created at the surface of the water. Carbon dioxide is mixed in the liquid under high pressure in the Carbonation process.