As civil engineers, it is essential for us to be aware of alkali-aggregate reactions. This phenomenon can have a significant impact on the stability, strength, and durability of concrete in structures over time. In this blog, we will explore the fundamentals of alkali-aggregate reaction, the effects of alkali-aggregate reaction on concrete, and the steps that can be taken to mitigate these effects.
What is Alkali-Aggregate Reaction
alkali-aggregate reaction is a process that occurs when the alkalis in concrete (i.e. the hydroxides and carbonates of sodium and potassium) react with the siliceous or siliceous and calcareous aggregates in concrete. This reaction can produce expansive products that can exert significant force on the concrete, leading to cracking, spalling, and ultimately, deterioration of the concrete.
There are two distinct types of alkali-aggregate reactions in concrete.
01. Alkali-silica reaction (ASR), which involves the reaction of certain silica minerals within the aggregate
02. Alkali-Silicate Reaction
03. Alkali-carbonate reaction (ACR), which involves the reaction of carbonate minerals
The effects of alkali-aggregate reaction on concrete are significant. Alkali aggregate reaction can cause cracking, spalling, and deterioration of concrete. In extreme cases, the alkali-aggregate reactions can cause the failure of concrete structures.
How to Prevent Alkali Aggregate Reaction
There are a number of steps that can be taken to mitigate the effects of the alkali-aggregate reactions. For example, proper selection of aggregates and cement, the use of low-alkali cement, and the inclusion of an alkali-resistant aggregate in concrete mixtures can all help to reduce the impact of alkali-aggregate reaction. In addition, regular monitoring of concrete structures for signs of alkali-aggregate reaction can help to identify potential problems early on, before they cause significant damage.
When it comes to alkali-aggregate reactions, knowledge is power. By understanding the phenomenon and its effects, we can take steps to mitigate its impact and protect the concrete structures that we rely on.
One or more of the ingredients of an attack must be changed in order to avoid AAR. It is required to stop the reaction or the expansion of the current AAR gel if there are no substitute ingredients.
- Decrease the alkali content
Use of the low alkali cement or we can replace the portion of cement with low alkali mineral admixtures.
- Use of non-reactive aggreges
- Reduce the content of water in hardened concrete
- Use of silica fume, fly ash, ground granulated blast furnace slag, etc. can reduce this reaction or eliminate it.
- Use of lithium compounds