PSI - Issue 70

Shashikant Kumar et al. / Procedia Structural Integrity 70 (2025) 501–508

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pioneering research work (Huang et al., 2013). By replacing ordinary Portland cement (OPC) with Class-C fly ash in their study, they demonstrated that upto 80 percent of the FA could effectively function as a binding material in concrete. However, Leung et al. (Leung et al., 2016) found that the combined impacts of FA and SF results in improved compressive strength after 28 days. 1.1. Research significance The outcomes of this study demonstrate that FA and SF are effective partial replacements for cement. In order to achieve this goal, an attempt has been made to examine the behaviour of SCC created using FA and SF as partial cement substitutes in this study. The hydration process of cement in the presence of various pozzolanic materials, which differ in specific surface area, chemical composition, and granulometric characteristics, has not been fully understood, particularly in the case of the silica fume-fly ash blend. The performance of self-compacting concrete (SCC) was assessed by examining its behaviour of fresh mix, mechanical characteristics, and microstructural properties using both binary and ternary blends. For determining the fresh properties of SCC, a series of key tests were conducted, including slump flow, T-500 time, J-ring flow, V-funnel time, and the L-box blocking height ratio. The compressive strength and split tensile strength tests were performed to evaluate the hardened properties of HVFA SCC. Additionally, X-ray diffraction (XRD) analysis and scan electron microscopic (SEM) image test were utilized to investigate the microstructural behaviour of HVFA-SCC. 2. Experimental investigation The experimental research was conducted in two stages. Tests were conducted in Stage 1 on binary mixes of SCC using FA and SF separately as a partial replacement of Ordinary Portland cement (OPC). Stage 2 examined the ternary mixes using FA and SF simultaneously to produce appropriate SCC. 2.1. Materials The current work has made use of OPC of grade 43, which conforms to IS: 8112-2013. The supplementary cementitious materials (SCM) FA and SF were used. Low calcium FA samples were given by the National Thermal Power Corporation (NTPC), Kahalgaon, and are utilized "as received" in the present investigation. FA samples satisfy the standards of IS: 3812-Part I. Condensed SF, commonly known as micro silica or SFs, is a supplementary pozzolanic material utilised in this experiment. Since SF is a substance that improves characteristics, it was chosen. South Asia's Elkem Pvt. The SF sample from Ltd. complied with IS: 15388. To assess the chemical configuration of the raw cement and filler materials, the X-ray diffraction (XRD) method was employed, as shown in Fig.1., Mullite, hematite and quartz phases were detected in FA, while portlandite, silicate, calcium carbonate, ettringite, and ferrite were discovered in SF. The fine aggregate utilized in this study was river sand sourced from the ‘Sone River’ in India, possessing a ‘water absorption’ capacity of 1.35% and a ‘specific gravity’ of 2.66. The coarse aggregate comprised crushed ‘Pakur stone’ with a 16 mm average s ize, exhibiting a ‘water absorption’ of 0.78% and a ‘specific gravity’ of 2.71. The physical properties of both aggregates were governed in accordance with the guidelines provided in IS 383:1970. For improving the workability of HVFA-SCC mix, a viscosity-modifying admixture (VMA) incorporated within a polycarboxylic ether- based superplasticizer was employed. The superplasticizer, marketed under the trade name ‘Master Glenium’ SKY 8630/8632, was supplied by ‘BASF India Limited’ and had a ‘specific gravity’ o f 1.06.

2.2. Mix proportion

The aim was to create high strength concrete, which IS 456-2000 defines as having a compressive strength more than 60 MPa. To overcome this challenge, a series of self-compacting concrete (SCC) mix design trials were systematically carried out, leading to the development of a controlled mix of HVFA-SCC with a water-binder ratio of 0.36. The water-binder ratio (0.36) did not change over the course of the study. The 40%, 50%, 60%, 70%, and 80% of cement was replaced with HVFA, and 2%, 4%, 6%, 8%, and 10% with SF as compared to control mix. Prior to