Does alkali react with carbonate?
The alkali–carbonate reaction is an alteration process first suspected in the 1950s in Canada for the degradation of concrete containing dolomite aggregates. The alkali-carbonate reaction could therefore also simply hide an alkali-silica or an alkali-silicate reaction. …
What causes ASR in concrete?
The primary cause of ASR is a reaction between the alkaline cement’s hydroxyl ions and some aggregate’s reactive forms of silica. This produces a hygroscopic gel which expands on the absorption of water, imposing pressure on the surrounding concrete and weakening it in a way similar to a freeze-thaw action.
What is alkali aggregate reaction explain?
Alkali–aggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and non-crystalline silicon dioxide, which is found in many common aggregates.
What is alkali silica reaction explain?
The alkali–silica reaction (ASR), more commonly known as “concrete cancer”, is a deleterious swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive amorphous (i.e., non-crystalline) silica found in many common aggregates, given sufficient moisture.
How are bicarbonate and carbonate related?
Bicarbonate is alkaline in nature and the conjugate acid of carbonate ion. On reacting with acids it releases carbon dioxide. The key difference between carbonate and bicarbonate is the charge on the compounds; carbonate has -2 charge and bicarbonate has -2 charge.
What do carbonates do?
The main uses of carbonates is as raw materials in different industrial processes such as drug development, glass making, pulp and paper industry, sodium chemicals (silicates), soap and detergent production, paper industry, water softener, clay and concrete production, among others.
Where does portland cement come from?
portland cement, binding material in the form of a finely ground powder, usually gray, that is manufactured by burning and grinding a mixture of limestone and clay or limestone and shale.
What is alkaline concrete?
Alkalinity in Concrete Slabs; The Real Culprit Healthy concrete has a high pH ~12.0 – pH 13.3. Alkalinity forms as a result of Portland cements reaction with water during the hydration phase. The excess (alkaline saturated) mix water moves towards the surface forming capillaries throughout the concrete.
What is alkali in cement?
The alkali content refers to the content of Na2O and K2O in cement. The condition for concrete to conduct the alkali-aggregate reaction is that the cement must contain alkali. When the active aggregate material is used, the cement with low alkali content should be used.
What are the two types of alkali-aggregate reaction?
This alkali-aggregate reaction has two forms: alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). Alkali-silica reaction (ASR) is of more concern because aggregates containing reactive silica materials are more common.
What is carbonation in cement?
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 difference in carbonate and bicarbonate?
Bicarbonate is alkaline in nature and the conjugate acid of carbonate ion. The key difference between carbonate and bicarbonate is the charge on the compounds; carbonate has -2 charge and bicarbonate has -2 charge.