Alkali-Silica Reaction in Concrete

Question 1

Alkali-Aggregate Reaction

Answer 1

1. Alkali-Silica Reaction (ASR)
2. Alkali-Carbonate Reaction (ACR)

Question 3

ASR 2 step process

Answer 3

1. alkali hydroxide + reactive silica = alkali-silica gel
2. alkali-silica gel + moisture =expansion

Question 4

3 Conditions for ASR

Answer 4

1. Moisture
2. reactive aggregates
   3.alkali (high PH)

Question 5

Prevent ASR

Answer 5

1. limit concrete alkali content
2. use right amount of SCM
3. use non-reactive aggregates
4. use ASR control admixture
5. reduce concrete permeability
6. type F fly ash

Question 6

Testing for ASR

Answer 6

• visiual : map cracking
  -spray surface with uranyl-acetate (appears bright yellow under UV)
• petrographic analysis: examine concrete under microscope

Question 7

ASR in existing concrete

Answer 7

1. seal it with silane
2. use lithium salt solutions
   - spray on surface
   -electrochemical impregnation