PSI - Issue 70

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

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Autogenous shrinkage stands as a primary drawback of High-performance concrete (HPC) because it contains low water-to-cement (w/c) ratios coupled with increased cementitious content (Wu et al., 2017). The self-desiccation process creates tensile stresses through shrinkage until microcracks appear thus damaging structure integrity and shortening service life (Snoeck et al.,2015). Researchers studied multiple bio-based agents as alternatives. The substantial mucilage content in aloe vera gel makes it effective for improving internal moisture and reducing cracking according to studies (Malathy et al.,2023). Studies demonstrated that natural hydrogel made from okra mucilage enhanced workability while preserving moisture content (Bedada et al.,2023; Lorika et al.,2023). The researchers extracted cactus mucilage and used it to control water release which reduced autogenous shrinkage in high performance concrete mixtures (Hashim et al.,2017; Vaidevi et al.,2022; Sekar, 2014). Formation of interior water storage elements inside concrete produces an efficient remedy for managing these issues. Internal curing agents release hydration moisture over time which preserves humidity levels inside the concrete mass while reducing tension effects and improving both mechanical strength and durability characteristics like pore refinement and permeability reduction along with freeze-thaw resistance (Chen et al.,2007; Daniel et al.,2020). Wet pre-wetted lightweight additives and superabsorbent polymers serve as common internal curing agents in concrete structures yet they present high costs and environmental issues because they are synthetic or mineral-derived materials (Zhou et al.,2024; Somers et al.,2021; Selvi,2020). The sustainable implementation of internal curing now uses bio based polymers particularly natural starches which originate from maize (corn) and cassava (tapioca) (Akindahunsi,2019). The starches demonstrate strong water retention capabilities accompanied by environmental friendly breakdown characteristics and favourable economic properties (Shao et al., 2022; Akindahunsi et al.,2015; Seeponkai, et al.,2024; Kulshreshtha, et al., 2017). The present research investigates corn and tapioca starch as internal curing agents in M40 grade concrete using a series of tests with cement weights ranging from 0.5 to 2%, with 0.25% increments. The study analyzes workability, strength development, shrinkage behaviour, and water absorption to establish the most sustainable internal curing conditions. 2. Materials and Experimental Approach The research incorporated OPC 53 grade cement according to IS 12269 (2013) standards along with manufactured sand as fine aggregate IS 383:2016 and 20 mm angular-shaped coarse aggregate which matched IS requirements for a clean and well-graded material. Portable water devoid of contaminants provided the mixture requirements and served as the curing agent. Two bio-based internal curing agents, corn starch together with tapioca starch were selected for experimental analysis. Two kinds of starches obtained locally served as the internal curing agents in gel form. The gel was prepared by heating starch with water. The internal curing agent was added at various dosages ranging from 0.5 to 2% by weight of cement, with 0.25% increments. The starch gel was added by partially replacing the batch water, ensuring that the total water content of the mix remained constant. Fig.1(a) and 1(b) illustrated the visual appearance of corn and tapioca starch. Table 1 provided the properties of starch.

Fig.1.(a).Corn strach

Fig.1(b). Tapioca starch