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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2.2. Testing methods Paste shrinkage was obtained by 25mm*25mm*285mm prism testing and assessed according to ASTM C490-04 (2004). After demolding, these prisms were displayed in an oven at an elevated temperature of 45±2°C. The shrinkage process was monitored using a dial gauge as shown in Fig. 2, with readings taken daily until a total period of 7 days. The shrinkage parameters as well as expansion are calculated using the following equation: = 0 − 200 ×10 6 (1) Where: LCH=Length change (µƐ) 0 = Initial length change reading = Length recorded at different days

Fig. 2. Dial Gauge.

3. Results and discussion 3.1. Drying shrinkage (DR-SH)

The progression of DR-SH over a duration of 7 days is illustrated in Fig. 3. Notably, there is an obvious reduction in the trend with the introduction of PA fibers. As the proportion of PA fibers increases, a corresponding decrease in DR-SH is observed. The most significant decline is achieved with the inclusion of 2% PA fibers, resulting in a 27% reduction compared to the control mix. This reduction is likely attributed to the sodium hydroxide (NaOH) treatment, which effectively eliminates all lignin and cellulose from the fibers. Thereby, it leads to enhancing structural bonding within the matrix (Manimaran et al. 2018; Khatib et al. 2022). Additionally, the PA fibers serve as thermal insulators at elevated temperatures, absorbing heat, and mitigating shrinkage effects (Thyavihalli Girijappa et al. 2019, Ghanem et al. 2024b).