Effects of added alkali hydroxides in mix water on long-term SO42− concentrations in pore solution
✍ Scribed by Sidney Diamond; Shaode Ong
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 832 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0958-9465
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✦ Synopsis
In ASR (alkali silica reaction) studies # has become common to pre-dissolve NaOH or KOH in the mix water to simulate the effects of high alkali content cements. It has been found that such treatment does not result in the expected augmentation of the OH-ion concentration, and much or all of the dissolved alkali hydroxide is immediately converted to alkali sulfate by reaction with gypsum. Much of the dissolved sulfate so produced remains in the pore solution under long-term exposure at 38°C, the common temperature employed in ASR studies. The concentration of S024 -ions produced at a given alkali hydroxide dosage varies with the specific hydroxide added, increasing in the order LiOH to NaOH to KOH. If ASR reaction is occurring, the SO~-ion concentration diminishes progressively with time. This effect was not due to progressive incorporation of sulfate in the ASR reaction product, as had been suspected. It may be due to secondary ettringite precipitation in ASRinduced cracks.