ACI investigated the long-term creep and drying shrinkage of three different 100% fly ash geopolymer concretes was carried out up to one year of age.
ACI says: “Two geopolymers, produced from Gladstone and Pt. Augusta fly ashes, achieved approximately 700 microstrain at the end of one year—equivalent to the total creep strain displayed by portland cement (PC) concrete.”
Additionally, the geopolymer concretes displayed a lower creep coefficient than PC concrete. Therefore, AS 3600 or the CEB-FIP model could be conservatively used to predict creep coefficient for two geopolymers.
However, Tarong fly ash geopolymer concrete differed significantly from the other geopolymers and achieved approximately 1900 microstrain after one year.
“The drying shrinkage of Gladstone and Pt. Augusta geopolymer concretes at one year are 175 and 190 microstrain while Tarong geopolymer and PC concrete achieved 615 and 475 microstrain,” ACI adds.
According to ACI, all fly ash geopolymer concrete showed lower drying shrinkage than the maximum permitted value recommended by AS3600. The incorporation of calcium-aluminasilicate-hydrate gel with the sodium-alumina-silicatehydrate geopolymeric gel positively affected the packing density of the gel phase.
“The degree of uniformity and compactness of aluminosilicate gel matrix together with the macroporosity in the 50 nm to 1?m range was identified as determining the long-term creep and drying shrinkage of the 100% low-calcium fly ash geopolymer concrete,” ACI concludes.
This paper was written by Chamila Gunasekera, Sujeeva Setunge, and David W. Law.