Studies of alkali-silica reaction. Part 3. Mechanisms by which NaCl and Ca(OH)2 affect the reaction

✍ Scribed by S. Chatterji; A.D. Jensen; N. Thaulow; P. Christensen

• Book ID: 107728353
• Publisher: Elsevier Science
• Year: 1986
• Tongue: English
• Weight: 533 KB
• Volume: 16
• Category: Article
• ISSN: 0008-8846
• DOI: 10.1016/0008-8846(86)90141-9

✦ Synopsis

Recently it has been observed that a concentrated solution of NaCl accelerates alkali-silica reaction and that the presence of free Ca(OH) 2 is a prerequisite for expansion to occur. This paper reports work done to understand the chemical processes involved. From the results of this investigation following mechanism has been proposed to explain the above observations. In the presence of free Ca(OH)2, Na + ions from alkali salts and OH-ions from Ca(OH) 2 together with water molecules penetrate reactive grains. Si-O-Si bonds in reactive grains are broken by penetrating Na + and OH-ions thereby opening the grains for further penetration of materials. At the same time silica ions tend to diffuse out of the reactive grains. Expansion occurs when more materials enter the reactive grains than diffuse out.