Experimental Investigation on Influence of Binder Constituents on Workability, Strength and Microstructure of SCGC

Abstract

The present study investigates the influence of bacteria on varying binder constituents to enhance the workability, strength, and microstructure properties of self-consolidating geopolymer concrete (SCGC). Geopolymer concrete is a sustainable alternative to conventional cement-based concrete, as it utilizes industrial by-products and reduces carbon emissions. The bacterial strains, known for their ability to promote mineral precipitation and improve concrete properties, are introduced in varying proportions to the geopolymer binder constituents. The goal of this experimental investigation is to better understand how Bacillus Cohnii bacteria affect the workability and strength of alkali-activated Self-consolidating Concrete (SCC) mix compositions. Three mix formulations with variable binder contents in the range of 400 kg/m3 and 450 kg/m3 were the subject of experimental research. This research work aims on investigating various binder constituents on Strength, Workability and Microstructure. Three different SCGC mixes were prepared by varying the percentage fly ash and Alcofine in range of 0%, 10%, 30% and 0%, 5%, 5% to the quantity of GGBFS respectively. Alcofine increases final setting time. For all mixes, ambient curing was done. As per EFNARC recommendations, the fresh qualities of SCGC were determined using the Slump test, T50 slump test, L-Box test, V- funnel test, and J-ring test. By conducting compression tests, split tensile tests, and flexure tests after 7, 14 and 28 days, the strength characteristics of SCGC were identified. The SCGC\'s microstructure and chemical composition were both determined by SEM and EDS analyses, respectively. According to test results, an alkaline solution sample with a 13M concentration and 450 kg/m3 of binder produced the highest compressive, flexural, and split tensile strengths after 28 days producing values of 58.32 MPa, 3.5 MPa, and 4.27 MPa, respectively.

Introduction

I. INTRODUCTION

Concrete is one of the most widely used construction materials, but its production involves a significant carbon footprint due to the cement binder's high energy consumption and CO2 emissions. In recent years, there has been growing interest in developing sustainable alternatives to traditional cement-based concrete. Geopolymer concrete has emerged as a promising eco-friendly alternative, utilizing industrial by-products or natural materials to create a binder that is environmentally friendly and exhibits favorable mechanical properties. The goal of this experimental investigation is to better understand how Bacillus Cohnii bacteria affect the workability and strength of alkali-activated Self-consolidating Concrete (SCC) mix compositions. The idea of enhancing concrete's strength using a microbiologically produced specific growth or filler is examined in this research. The bacteria Bacillus Cohnii was used in this experiment (5). One of the essential factors in concrete is its workability, which refers to its ability to flow easily and self-compact without the need for external energy. Self-consolidating concrete (SCC) addresses this concern, ensuring excellent workability and reducing the need for vibration during casting. Integrating bacteria in concrete production has gained attention for its potential to enhance various properties of concrete through a process called bacterial concrete mineralization. The objective of this research is to experimentally investigate the influence of bacteria on varying binder constituents in self-consolidating geopolymer concrete. The study aims to analyze the effects of bacteria on workability, strength characteristics and microstructure of the concrete, with the ultimate goal of developing a more sustainable and high-performance construction material.

Utilising SCGC lowers maintenance costs and raises building quality overall [8]. A limited number of SCGC-related studies are currently being done. Superplasticizer addition improves SCGC's workability and strength [9]. SCGC mixes are created in accordance with EFNARC standards [10]. In this experiment, 6 distinct SCGC mixtures were created to examine the effects of differing binder ingredients (400 kg/m3 and 450 kg/m3) and the molarity of NaOH liquid (13M) on the workability and strength characteristics of SCGC.

II. MATERIALS AND METHODOLOGY

A. Materials Used

Fly ash (FA), ground granulated blast furnace slag (GGBFS) and alccofine were used in the production of SCGC. Class F fly ash, GGBFS, and alccofine were purchased from Ultratech RMC plant Peenya in Bangalore, Karnataka, India. The chemical and physical characteristics of the components that make up a binder are shown in Tables 1 and 2, respectively. Alkaline activator liquids were purchased and utilised to prepare samples by Panacea Agrochemicals.  Na2SiO3 solution with 54% water content and NaOH flakes with a 95% purity. Na2SiO3 solution's characteristics are shown in Table 3. M-sand was used as the fine aggregate, and Ultratech RMC facility Peenya also provided the coarse aggregate, which was divided into pieces of 20 mm while 12.5 mm in a ratio of 60:40. The bacterial agent, typically Bacillus Cohnii will be selected for its ability to induce calcium carbonate precipitation. According to IS 383:2016 [12], tests on coarse aggregate and M-sand were conducted. The results are listed in Table 4. SCGC was prepared using BASF Masterglenium 8233, a polycarboxylic ether-based superplasticizer that complies with IS 9103 [13]. Superplasticizer's properties are shown in Table 5.

Conclusion

1) The effect of Bacillus Cohnii bacteria on the workability, strength, and microstructure analysis of self-consolidating geopolymer concrete (SCGC) is examined in this experimental study. 2) The workability, strength, and microstructure of SCGC were improved by the addition of Bacillus Cohnii bacteria at a cell concentration of 3% of the total binder content. 3) This experimental study shows that addition of Bacillus Cohnii bacteria enhanced slump flow by 6.1%, compression strength by 21.7%, split-tensile strength by 64.1% and flexural strength by 6%. 4) Incorporation of Bacillus Cohnii bacteria improved bio-mineralization process which is evident through SEM and EDS analysis.

References

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Copyright

Copyright © 2023 Monisha HB, Dr. Nayana N. Pati. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.