PSI - Issue 70

S. Rajeshkumar et al. / Procedia Structural Integrity 70 (2025) 287–294

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4.2. Mechanical Performance of Concrete with RHA and GSA. The impact of substituting cement with RHA and GSA on the mechanical behaviour of M30 grade concrete was studied in this study. The mixes were evaluated for their strength characteristics at various curing ages. The test outcomes are represented in Table 3. The compression strength of concrete mixtures enhanced with the partial substitution of cement with RHA and GSA, achieving an optimal level, as illustrated in Fig. 3. The control concrete (CC) reached 33.90 MPa after 56 days. The concrete mix containing 15% RHA and 10% GSA achieved the maximum strength of 43.23 MPa among all compositions tested. RHA and GSA combined to produce increased formation of C S-H gel that effectively filled empty spaces to strengthen the material (Nwofor and Sule 2012). R25G0 experienced a minimal reduction when the replacement level exceeded its ideal point. The strength reduction might be because of too much ash content disturbing the cementitious reaction. The appropriate pozzolanic material contents improve strength values but excessive amounts lead to strength reduction (Mahmoud, et al.,2012; Sathiparan et al.,2023).

Fig.3. Test findings on compressive strength

Fig.4 Test findings on split tensile strength

Fig.4 exhibits the test findings from split tensile strength for all mixtures. The incorporation of RHA and GSA enhanced the split tensile strength in concrete samples. The R15G10 mix exhibited better split tensile strength results at 28 days with 3.50 MPa compared to the control mix that obtained 2.85 MPa. The incorporation of ashes contributed to tightened concrete structure by helping fill empty spaces. The strength increment diminished slightly as the replacement quantity increased (Habeeb and Fayyadh 2009; Obilade,2014). The control mix (CC) reached 4.62 MPa flexural strength at day 28. The mixture R15G10 demonstrated the most significant strength of 5.25 MPa because it enhanced crack resistance while distributing loads more effectively. The combined pozzolanic activity of RHA and GSA created a stronger cement microstructure that resulted in increased flexural strength. R25G0 showed a minor strength reduction at 4.68 MPa likely because an excessive amount of substitute restricted the hydration reactions. The concrete mixes demonstrated a progressive increase in elastic modulus through RHA and GSA additions until reaching their maximum value. The control mix (CC) achieved a modulus of 27.8 GPa as it reached 28 days. The mix R15G10 achieved the highest value of 32.1 GPa for stiffness and deformation resistance. The concrete mixes gained strength because the denser microstructure from pozzolanic reactions combined with better particle packing. The elastic modulus values of R10G15 and R20G5 exceeded those of the control mix by reaching 30.1 GPa and 29.4 GPa respectively. The excessive replacement in R25G0 led to a decrease in elastic modulus to 28.2 GPa because the cementitious binding capacity became weaker. The experimental results showed that the range of elasticity modulus extended between 27.8 GPa and 32.1 GPa thus validating the positive influence of using moderate amounts of RHA and GSA. 4.3. Durability Behaviour of Concrete with RHA and GSA The performance duration of concrete depends heavily on its durability factor when exposed to various environmental conditions. The research evaluated concrete durability properties through the analysis of concrete made with RHA