- Author
- Wells, L. S. | Clarke, W. F. | Levin, E. M.
- Title
- Effect of Aging on the Soundness of Regularly Hydrated Dolomitic Lime Putties.
- Coporate
- National Bureau of Standards, Washington, DC
- Report
- BMS 127, April 25, 1952, 16 p.
- Keywords
- aging (materials) | plaster | hydration
- Abstract
- Regularly hydrated dolomitic limes are potentially unsound because they contain unhydrated magnesia that may hydrate subsequently in the set plaster, causing disruptive expansion. It is important to know the time required to soak these limes as putties so that sufficient magnesia will have been hydrated to give a sound putty. The customary soaking period of 1 day is inadequate, as evidenced by the prevalence of white-coat expansion failures. Consequently, the progressive hydration of magnesia in dolomitic lime putties upon aging and the attendant decrease in autoclave expansion of cement-lime putty bars were studied for 18 regularly hydrated dolomitic limes representative of commercial production. The limes differed markedly in regard both to the time required to reach a given percentage of expansion and to the extend of hydration at the given expansion. The shortest time of aging required to reduce the expansion to 1 percent (a suggested specification limit for soundness) was 3 weeks, whereas the longest time was in excess of 32 weeks. When the expansion had been reduced to 1 percent, the proportion of total magnesia hydrated ranged form 82 to more than 97 percent. Inasmuch as long and variable aging periods are impractical, suitable alternates, including the use of newly developed sound hydrated limes, are discussed.