PSI - Issue 64

Rawan Ramadan et al. / Procedia Structural Integrity 64 (2024) 1927–1934 Author name / Structural Integrity Procedia 00 (2019) 000–000

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1. Introduction Reducing shrinkage in cement-based systems is a challenge in construction applications. When the volume decreases during the curing process, it can lead to problems like cracks and compromised durability over time. Concrete technology research has extensively studied factors, including the use of supplementary cementitious materials (SCMs) to control shrinkage induced cracking. SCMs like fly ash, silica fume, slag, etc.. have been investigated for their potential to reduce shrinkage (Kurdi et al. 2001; Hasnaoui et al. 2021; Yang et al. 2021; Ramadan et al. 2022; Qin et al. 2022, Ghanem et al., 2024a). In recent years, researchers have been looking into sustainable options and have found that using bio fibers in cement mixes could be a great solution to reduce shrinkage issues. These bio fibers, which come from sources, like plants (jute, sisal, banana, hemp) or agricultural waste are getting a lot of attention because they can improve the strength of concrete and minimize shrinkage (Khelifa et al. 2018; Kessal et al. 2023). The integration of bio fibers does not only address sustainability concerns but also improves tensile strength and crack resistance, which offers two advantages in managing shrinkage related challenges. Ongoing, research aims to refine the use of bio fibers as environmentally friendly solutions for enhancing both durability, sustainability and managing shrinkage in cement - based materials (Mal and Narine. 2004; Eller et al. 2017; Packer et al. 2017). One of these efficient plants is named by Phragmites australis (PA). This plant has recently been explored and has shown a significant effect in reducing shrinkage in paste and mortar mixes (Ramadan et al. 2023a; Ramadan et al., 2023b; Khatib et al. 2024). PA is widely available and has a low cost, making it a cost-effective option for use as fibers in concrete. Although this plant is invasive and usually causes problems for farms. Therefore, it is beneficial to use it as fibers in concrete. Researchers have studied this plant in cementitious materials and showed that the addition of 2%PA by volume of mix reduced the shrinkage of mortar (Ramadan et al. 2023a; Khatib et al. 2024). Another study focused on the role of using these fibers on the reinforced concrete (RC) beam performance and in this study, it was found that the addition of 0.5% PA fibers had a higher ductility index compared to the control mix (Ramadan et al. 2023b). The interaction between bio-fibers and cement matrix has been a subject of research, exploring the optimal dosage and compatibility to achieve the desired improvements in performance. As the construction industry increasingly prioritizes environmentally friendly practices, the integration of bio-fibers offers a dual advantage by addressing both sustainability concerns and shrinkage-related challenges in cementitious systems. Therefore, the aim of this study is to explore the advantage of adding PA fibers in reducing shrinkage of cement paste at elevated temperature (45°C).

Nomenclature PA

Phragmites-Australis

SCMs

Supplementary cementitious materials

DR-SH Drying shrinkage AUTO-SH Autogenous shrinkage EXP Expansion LCH Length change

2. Materials and Testing Methods 2.1. Materials

The raw materials used in this study are Portland cement type I referred to as Sibline manufacturing dat. The fibers are from PA plant. These fibers were collected from Litani river (Bekaa-Lebanon). After the collection of this plant, the stems were sun-dried, cut into 10 mm length and 2 mm wide and stocked in bags. The PA fibers were prepared for treatment by sodium hydroxide (NaOH) for 24 hours. After that, the PA fibers were washed, sun-dried once again, and then stored in bags (see Fig.1). These fibers have a density of 0.65 g/cm 3 . The mixture proportions are found in Table 1.