53 WORKABILITY AND STRENGTH CHARACTERISTICS OF ALKALI-ACTIVATED FLY ASH/GGBS CONCRETE ACTIVATED WITH NEUTRAL GRADE Na 2 SiO 3 FOR VARIOUS BINDER CONTENTS AND THE RATIO OF THE LIQUID/BINDER GUGULOTHU VIKAS PAUL 1* , T. D. GUNNESWARA RAO 2 Address 1 Dept. of Civil Engineering, Christu Jyothi Institute of Technology & Sciences, Jangaon, Telangana, India. 2 Dept. of Civil Engineering, National Institute of Technology, Warangal, India. * Corresponding author: [email protected] Abstract Alkali-activated fly ash/GGBS concrete (AAFGC) is a new blend- ed concrete that has been studied by many researchers due to its environmental advantages and better technological character- istics. However, the effect of various factors on AAFGC fresh and hardened properties has not yet been thoroughly studied. The lit- erature mainly describes the combination of NaOH and Na2SiO3 as an activator for the AAFGC’s activation, but alkali-activated GGBS concrete (AAGC) prepared with this activator solution is less workable due to its rapid setting behaviour. In this study, AAFGC was prepared using neutral grade liquid Na2SiO3 with a SiO2/ Na2O ratio of 2.92. An experimental program was performed for fly ash-GGBS combinations (100-0, 50-50, 0-100), solution/ binder ratios (0.6, 0.65, 0.7) and binder contents (300, 400 and 500 kg/m3) to evaluate the workability and the compressive and tensile strength of AAFGC. The results of this study show that a water glass of 2.92 silica modulus used as an activator to prepare AAFGC under ambient curing is very useful in the construction industry. Key words ● Alkali-activated fly ash/GGBS concrete, ● Neutral grade liquid Na 2 SiO 3 , ● Initial and final setting time, ● Workability, ● Tensile strength. 1 INTRODUCTION After water, concrete is the most widely-used material in the world, and its use increases with urbanization. The main problem in the cement industry is that the manufacturing process of ordi- nary Portland cement (OPC) emits large amounts of carbon diox- ide (CO 2 ) into the atmosphere. Cement CO 2 emissions contribute to 90% of the global CO 2 emissions by industrial processes (Xi and Davis, 2016), and OPC total industrial emissions account for about 8% of the CO 2 emissions worldwide [Le and Andrew, 2016; Le and Andrew, 2017; Andrew, 2018). Attempts have been made to produce alternatives to cement, such as cement-less concrete. Alkali-activated materials are one of those alternative binders in which cement can be substituted by fly ash and GGBS that are obtained during the production of coal and iron. Research on the development of alkaline-activated materials has aroused great in- terest for the scientific community over the last twenty years, as these products are expected to become a sustainable alternative to Portland cement binders (Provis, 2014). An alkali-activated concrete is formed when supplementary cementitious materials, such as fly ash, GGBS, rice husk ash, metakaolin, etc., are acti- vated with an alkaline solution (Midhun et al., 2018; Wongpa et al., 2010; Venu and Rao, 2017). Arivalagan (2014) concluded that GGBS can be used as an alternative to cement as it reduces the use of cement and construction costs. The alkali activation of fly ash binder with an activator prepared with sodium hydroxide and liquid Na 2 SiO 3 , which requires a high concentration of NaOH and heat curing, has been proposed to increase the initial age strength of alkali-activated fly ash concrete (AAFC) (Mustafa et al., 2011). The alkali activation of a GGBS binder can produce high strength AAGC without oven curing, but the main problem with GGBS is the rapid setting behavior of the concrete, which results in low Vol. 30, 2022, No. 3, 53 – 64 DOI: 10.2478/sjce-2022-0021 Slovak Journal of Civil Engineering © 2022 The Author(s). This is an open access article licensed under the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/).
WORKABILITY AND STRENGTH CHARACTERISTICS OF ALKALI-ACTIVATED FLY ASH/GGBS CONCRETE ACTIVATED WITH NEUTRAL GRADE Na2SiO3 FOR VARIOUS BINDER CONTENTS AND THE RATIO OF THE LIQUID/BINDER
May 03, 2023
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