PSI - Issue 70

Kavitha E. et al. / Procedia Structural Integrity 70 (2025) 588–595

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1. Introduction Concrete is a universally used material across various construction applications. Ordinary Portland Cement (OPC), the primary binder in concrete, is associated with significant greenhouse gas emissions, leading to serious environmental impacts which leads to severe environmental disorder (Anvari et al 2022). In order to overcome the issue, the cement composite based new innovative material i.e geopolymer were produced. Geopolymer composites' raw ingredients entirely replace the cement, produce carbon footprints that are negative, and use less energy (Hemn Unis et al 2022). As per different research approximately eighty percentage of carbon emission was reduced in usage of geopolymer binder because of raw source of alumina silicates which possess the behaviour of small amount of embodied carbon and it produce environmentally friendly binder (Tayeh et al 2021). Geopolymer binder is composed of cementitious supplementary by products and alkaline solution as a catalyst. In geo-polymerization mechanism, the most significant chemical products the sodium silicates acts strongly as catalyst as well as sodium hydroxide pellets acts as reactants. The strength characteristics of geopolymer are mainly depends on the parameters of ratio of sodium silicates to sodium hydroxide and NaOH molarity (Budh et al 2014). The specimen of geopolymer with fly ash and GGBS as cementitious material enhances the strength with increase of molarity of NaOH (Rachamalla et al 2020). The polycondensation reaction of alumino-silicate-oxide with alkali polysialates produces polymeric Si-O-Al linkages and produce a matrix of geopolymer as part of the geopolymer mechanism. Similar to C-S-H gel of conventional concrete hydration product more polymer is produced (Davidovits J 1994). The sustainable based geopolymer is categorized into numerous types, one of which is fibre-based concrete. The mechanical characteristics of concrete could be enhanced by reinforced with various fibres such as synthetic, steel, glass, carbon and natural fibres. The fibre incorporated concrete is composite one which consists of two or more materials and it will improve the tensile characteristics, strain behavior of brittleness in concrete and arrest the crack growth. (Rajkohila et al 2024). Many investigations were carried out on using of synthetic fibres as reinforcement material in concrete or geopolymer mortar or concrete and it could perform good interface adhesion in the matrix of geopolymer (Mashhadani et al 2018). Nowadays in construction sector there is budding towards the energy efficient technique, sustainable development, renewability, easy processing and low-density nature which led to increase the importance in using natural alternative fibre over the synthetic materials (H.Ye and Assaedi 2018). A lot of studies were focused to examine the various types of natural fibres performance and behaviour in geopolymer binder by treating the surface of fibre to enhance the composite methodology (Marfa et al 2020). The natural fibres which are used as reinforcement in RCC and Geopolymer are divided into plant and animal fibres. The different natural fibres are investigated in concrete as reinforcement materials were sugarcane bagasse, palm, sisal, kenaf, jute, flax, hemp, bamboo fibre and coir or coconut fibre (Ampol et al 2020). Omar et.al 2023 studied with three natural fibres such as jute, bamboo and hemp as reinforced in geopolymer which exhibits good mechanical, resistance to fire, thermal and sound insulation characteristics as well as enhanced their sustainability in the construction sectors with proper surface modification treatment. The investigation is performed by Yan.et al 2016 and Zaman. et al 2013 using coir which is extracted from coconut and is used as natural fibres. The coir is used as treated and untreated in geopolymer binder which shows the treated coir exhibits better improvement in mechanical characteristics when compared both coir with plain concrete. In fly-ash based geopolymer binder with different % of cotton fibre in 0.3, 0.5, 0.7 and 1 by the weight were added to evaluate the properties and crack pattern of composites the result shows the geopolymer composites with 0.5% can enhance and improve the properties of mechanical strength (Alomayri et al 2013). The one percentage weight of four fibres such as cotton, coir, sisal and raffia were incorporated in geopolymer binder by Korniejenko et al 2016 to examine the heterogeneous structures, flexural and compressive properties. From the evaluation the composites with natural fibre can increase its strength properties. This paper is focused to study on effect of neem fibres which is used as natural fibre on the mechanical as well as durability behaviour of geopolymer composites. Neem tree is considered as native to India as well as available in more continent which is found abundant in quantity. By using the neem barks, neem twigs and leaves the natural neem fibres are manufactured which are renewable resources, biodegradable one and reducing the environmental imapcts. Hence