Reinforced and plain geopolymer concrete specimen cross-section composition influence on creep strains

Low calcium alkaline solution activated cement composite, or geopolymer concrete has been around for about 40 years. The main benefit of this material - it is partially made by utilising waste products, such as fly-ash, slags and others. It has been claimed that the manufacturing of various geopolymer binder produces up to 6 times less CO2 than the production of Portland cement. Because of the nature of the binding process of the geopolymer concrete, there are some differences in the cause of the shrinkage. Because of this aspect, the long-term property development mechanism is slightly different, and the microstructure of the specimen could be different than for ordinary Portland cement. Although the researches regarding the geopolymer concrete composition and mechanical properties have significantly been reviewed in the previous couple of years, there has been a lack of investigations regarding the long-term properties and the conditions affecting and influencing long-term properties of the geopolymer concrete. Two geopolymer concrete mixes are the test subject for this article - plain geopolymer and reinforced geopolymer with 1% waste steel fibers that have been subjected to creep and shrinkage tests. Waste steel fibers are the by-product of the car tire recycling process. The steel industry is not willing to take them, but if recycle these products they can be used as fiber reinforcement. The microstructure analyses with SEM were done by analysing specimens polished sections. Afterward acquired images of specimen cross-sections were analysed by determining the amount of fiber, geopolymer binder, filler, and air void amount in analysed cross-section. The results were cross-referenced with creep and shrinkage test results of analysed specimens. The aim of this article is to determine the loading influence and geopolymer concrete microstructure influence on long-term properties by evaluating polished specimen sections