Abstract
Geopolymer concrete (GPC), also known as an earth friendly concrete, has been under continuous study due to its environmental benefits and potential as a sustainable alternative to conventional concrete construction. However, there is still a lack of comprehensive studies focusing on the influence of all the design mix variables on the fresh and strength properties of GPC. GPC is still a relatively new material in terms of field application and has yet to secure international acceptance as a construction material. Therefore, it is important that comprehensive studies be carried out to collect more reliable information to expand this relatively new material technology to field and site applications. This research work aims to provide a comprehensive study on the factors affecting the fresh and hardened properties of ambient cured fly ash and slag based geopolymer concrete (FS-GPC). Industrial by-products, fly ash from thermal power plants, and ground granulated blast furnace slag from steel industries were utilized to produce ambient cured FS-GPC. A series of experiments were conducted to study the effect of various parameters, i.e., slag content (10%, 20%, 30%, and 50%), amount of alkaline activator solution (AAS) (35% and 40%), sodium silicate (SS) to sodium hydroxide (SH) ratio (SS/SH = 2.0, 2.5 and 3.0), sodium hydroxide concentration (10 M, 12 M, and 14 M) and addition of extra water on fresh and mechanical properties of FS-GPC. The workability of the fresh FS-GPC mixes was measured by the slump cone test. The mechanical properties of the mixes were evaluated by compressive strength, split tensile strength, flexure strength, and static modulus tests. The results revealed that workability of FS-GPC is greatly reduced by increasing slag content, molarity of NaOH solution, and SS/SH ratio. The compressive strength was improved with an increase in the molarity of NaOH solution and slag content and a decrease in AAS content from 40% to 35%. However, the influence of SS/SH ratio on mechanical properties of FS-GPC has a varying effect. The addition of extra water to enhance the workability of GPC matrix caused a decrease in the compressive strength. The validity of the equations suggested by previous studies to estimate the tensile and flexural strength and elastic modulus of FS-GPC mixes were also evaluated. Based on the test results of this study, empirical equations are proposed to predict the splitting tensile strength, flexural strength, and elastic modulus of ambient cured FS-GPC. The optimal mixtures of FS-GPC in terms of workability and mechanical properties were also proposed for the field applications.
Highlights
Over the last two decades, constructional activities have been growing rapidly around the globe due to increased infrastructure demand
Since sodium silicate has more viscosity than sodium hydroxide in activator solution (AAS), higher SS/SH ratio led to more viscous AAS which resulted in lower slump values of FS-Geopolymer concrete (GPC) mixes [28]
Concluding Remarks This paper presented the results of an experimental program conducted to evaluate
Summary
Over the last two decades, constructional activities have been growing rapidly around the globe due to increased infrastructure demand. The results of this study do not apply to the alkali activated fly ash and slag blended geopolymer concrete since only slag was used as a source material to produce GPC. The strength of GPC mix is dependent generally on various ingredients and their ratios, i.e., type of source materials like FA, SG, and alkaline activators, activating solution content, curing methods, mixing procedure, concentration of alkaline solution etc.; this makes it challenging to design it against a specified target strength. This research work aims to provide a comprehensive study on the main factors affecting the workability and mechanical properties of fly ash and slag based geopolymer concrete (FS-GPC). These equations can be used to provide prediction of tensile, flexural strengths, and modulus of elasticity of FS-GPC mixes having 28 days compressive strength in the range of 30–60 MPa
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