EXPERIMENTAL STUDY ON DRYING, AUTOGENOUS AND RESTRAINED SHRINKAGE STRAINS OF ALKALI-ACTIVATED FLY ASH GEOPOLYMER CONCRETE

Abstract

This paper presents novel experimental results on the drying, autogenous, and restrained shrinkage strains of one-part alkali-activated geopolymer concrete (AAGC). Five geopolymer concrete mixtures and three ordinary Portland cement concrete mixtures were cast and studied. The impact of the ratio between the alkali activator and the total amount of fly ash and ground granulated blast furnace slag (ACT/FG), along with the total content of FG on the compressive strength and drying shrinkage of AAGC, was examined. The results indicated that the compressive strength of AAGC improved with rising calcium and silica content in the binder. The 28-day compressive strength of AAGC ranged from 31.6 MPa to 48.6 MPa. An increase in the alkaline activator from 6% to 10% can result in a 40.4% increase in compressive strength. Conversely, the amount of alkali activator had a minor impact on the drying shrinkage of AAGC. The 120-day drying shrinkage of AAGC specimens was 2.3 to 4.0 times greater than that of OPCC samples. A reinforcement ratio of 1.13% can reduce the drying shrinkage strain of AAGC by approximately 4.0 to 5.0 times. The experiment demonstrated that OPC mixtures outperformed GPC regarding the first crack appearance. The GPC mixtures cracked earlier but displayed small cracks that did not propagate towards the steel ring. The inclusion of drying, autogenous, and restrained shrinkage provides a well-rounded perspective, which is critical for structural applications of GPC.