Shrinkage and Creep of Concrete Containing 50% Lignite Fly Ash at High Temperatures

Abstract

Abstract This paper investigates the influence of high temperature on the shrinkage and creep of unsealed and sealed concrete containing 50% Saskatchewan lignite fly ash and 50% Type I portland cement. Concrete was tested at six different temperatures between 70 and 450°F (21 and 232°C) and under three stress levels of 750, 1200, and 1500 psi (5.2, 8.3, and 10.3 MPa). The tests were made on 3 by 9-in. (75 by 225mm) concrete cylinders, and shrinkage and creep were measured for a maximum period of 112 days. It was found that the shape of the shrinkage and the creep time curves were similar at both normal and elevated temperatures. Test results also showed that shrinkage and creep of unsealed specimens decreased with a rise in temperature from 70 to 350°F (21 to 177°C) and then increased with a further rise in temperature. Creep of sealed specimens was found to increase with a rise in temperature from 70 to 160°F (21 to 71°C) and then to decrease with a further rise in temperature. Shrinkage and creep of unsealed specimens were nearly the same as those of plain concrete at the age of 112 days and at temperatures of 70 to 450°F (21 to 232°C).