Optimization of a geopolymer mixture for a reinforced cantilever concrete bench

Abstract

Traditional Ordinary Portland cement (OPC)-based concrete consumes large quantities of natural resources for its production, which is
highly energy intensive and has high CO2 emission. Therefore, development of the geopolymer concrete, based on use of industrial byproducts,
can provide an environmentally friendly and low-carbon alternative to OPC concrete. Geopolymer concrete characterized with
low permeability, mechanical properties and excellent heat resistance, has been receiving increasing attention in building industry
nowadays.
However, there are some challenges regarding the structural application, such as adjusting the fast setting time, tailoring the workability,
and controlling the shrinkage of blast furnace slag based geopolymer concrete.
The main aim of this study is to design and optimize geopolymer concrete mixture for manufacturing a reinforced cantilever bench. This is
accomplished by testing rheological and mechanical properties, and the drying shrinkage of geopolymer concrete.
The geopolymer binder consisted of fly ash (FA), blast furnace slag (BFS) and activator. The activator was made by mixing sodium
hydroxide and waterglass solutions. The prolonged setting time of the studied mixture was achieved by using proper type and amount of
chemical admixture in order to achieve enough time for casting but not to affect mechanical properties of the hardened concrete. The
compressive strength, elastic modulus, flexural strength, drying shrinkage and the effects of curing duration were evaluated.
The application of the optimized geopolymer mixture in the complex structural element such as cantilever bench has shown promising
results. Such small scale application and low risk project was suitable to gain the experience and confidence with this innovative type of
material for which no international codes or regulations are available. Furthermore, this project has proven to be encouraging for further
upscaling of geopolymer concrete for larger scale structural applications, like bridges and/or other structural elements in the building
industry.