PSI - Issue 70

Surya Mouli R. et al. / Procedia Structural Integrity 70 (2025) 239–246

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brought by gel incorporation. Higher dosages of gel might have introduced more water into the system as well as disrupted cement paste continuity resulting in decreased performance. (Tan et al.,2017). 4.4 Modulus of Rupture The concrete mixtures exhibited an increased modulus of rupture until starch gel dosage reached its maximum value after which it started decreasing again. The flexural strength of concrete mixes containing 1.0% corn starch gel reached its highest level of 3.90 MPa and 5.85 MPa while the control mix had values of 3.50 MPa (7 days) and 5.28 MPa (28 days). The strength values started decreasing after reaching peak values at the specified dosage point. The tapioca starch gel (TS) achieved its highest values at 1.0% dosage which resulted in 4.00 MPa at 7 days and 5.94 MPa at 28 days, as exhibited in Fig.5. Internal curing together with sustained hydration was enhanced by the gel network during the initial period of improvement. The same combination of factors such as increased water requirement and deteriorated interfacial attachment between components likely caused modulus of rupture to diminish. The flexural performance improved positively when using both starch types until reaching their optimum levels.

Fig.5 Modulus of rupture results

Fig.6. Drying shrinkage of various mixes

4.5 Drying Shrinkage The drying shrinkage values for all mixtures were noted to diminish with the incorporation of starch gel up to a specific dose, beyond which they steadily increased, as shown in Fig.6. In corn starch (CS) mixtures, the shrinkage decreased from 0.081 mm in the control mix (CM) to a minimum of 0.060 mm at a 1.0% dosage. The measured shrinkage values followed an upward trend from 2.0% onward to reach a maximum value of 0.076 mm. Among the