PSI - Issue 70

C. Manoj Prabhu et al. / Procedia Structural Integrity 70 (2025) 207–214

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The control mix (CM) exhibited the highest absorption rate at 3.78%, whilst the 12M-25 mix demonstrated the lowest at 2.42%. The decrease in WB results from the pozzolanic reaction of RHA, enhancing particle packing and refining the pore structure (Kim et al, 2014). Moreover, molarity significantly influences permeability. The 12M mixes demonstrated consistently reduced water absorption compared to the 10M mixes, suggesting that increased NaOH content promotes geopolymerization, leading to a more compact microstructure (Davidovits, 2008). The combination of increased molarity and increased RHA content significantly diminishes moisture penetration, hence enhancing the overall durability of GPC.

Fig.3.Test findings on water absorption test

4.2. Sorptivity Test Sorptivity measures the rate of capillary water absorption in concrete. Figure 2 illustrates the variation in sorptivity over different levels of RHA replacement and molarities. The findings demonstrate a progressive reduction in sorptivity as RHA level increases. The control mix (CM) had the maximum so rptivity at 0.090 mm/min⁰.⁵, while the 12M- 25 mix demonstrated the lowest at 0.070 mm/min⁰ . ⁵ . The decrease in sorptivity results from the pozzolanic impact of RHA, which enhances the pore structure and diminishes capillary voids (Kim et al, 2014). Moreover, increased molarity promotes geopolymerization, resulting in a more compact matrix and reduced permeability. The 12M mixtures regularly shown reduced sorptivity compared to the 10M mixtures, corroborating that a higher NaOH concentration enhances water resistance (Davidovits, 2008). This enhanced resistance to water penetration increases the longevity and durability of GPC constructions. 4.3. Rapid Chloride Penetration Test (RCPT) RCPT assesses the resistance of concrete to chloride ion penetration, influencing its durability. Figure 3 illustrates the fluctuation in RCPT values corresponding to various RHA substitutions and molar concentrations. The control mix (CM) exhibited the maximum charge passed (2350 Coulombs), signifying moderate chloride permeability according to ASTM C1202 (1000 – 2000 Coulombs for low permeability, 2000 – 4000 Coulombs for moderate permeability. The RCPT values for 10M mixes ranged from 2045 Coulombs to 1510 Coulombs whereas 12M mixes ranged from 1995 Coulombs to 1480 Coulombs. All geopolymer concrete (GPC) sample exhibited minimal chloride permeability in accordance with ASTM C1202. With the rise in RHA concentration, RCPT values lowered, attaining