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Creep, shrinkage and permeation characteristics of geopolymer aggregate concrete: long-term performance

Seneviratne Charitha, Gunasekara Chamila, Law David W., Setunge Sujeeva, Robert Dilan

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 4

633--647

The long-term impact on creep, drying shrinkage, and permeation characteristics of an innovative concrete produced with manufactured geopolymer coarse aggregate (GPA) has been investigated and compared with quarried Basalt aggregate concrete. Microstructure and pore-structure development up to 1 year were examined through scanning electron microscopy, nanoindentation, and X-ray computed tomography. Compressive strength and elastic modulus of GPA concrete varied from 34.6 to 50.8 and 18.5 to 20.5 GPa, respectively, between 28 and 365 days. The 1-year creep strain of GPA concrete was 747 microstrain while the calculated creep coefficient was 0.97, which is significantly lower than the creep coefficient predicted by AS 3600 and CEB-FIP models. Moreover, the 365-day drying shrinkage is 570 microstrain, which is also lower than the maximum permissible limit specified by AS3600. The GPA concrete displayed high water absorption, but lower air and water permeability compared to Basalt aggregate concrete. This is attributed to a porous surface layer with large number of capillaries increasing the water absorption of GPA concrete through capillary suction. The discontinuity in the pore network coupled with a condensed interfacial transition zone formed in GPA concrete could be the reason for lower permeability. Overall, the long-term performance of the GPA demonstrates a potential as a lightweight coarse aggregate for concrete, with the added advantage of reducing the environmental impact utilizing fly ash from coal-fired power generation.