Assessment of strength development mechanisms in pond ash geopolymer concrete under different activator and curing conditions
摘要
The growing demand for sustainable construction materials has accelerated research into geopolymer concrete utilizing industrial by-products as alternative binders. This study investigates the compressive strength development of pond ash-based geopolymer concrete by evaluating the influence of key mix parameters, including sodium hydroxide (NaOH) molarity (12 M, 14 M, and 16 M), Na2SiO3/NaOH ratio (2.0–2.25), curing temperature (60–80 °C), and pond ash content (375–400 kg m−3). Eighteen geopolymer concrete mixtures were prepared and tested for compressive strength at 7, 14, and 28 days to assess both early-age and long-term performance. The experimental results demonstrated continuous strength development with curing age, confirming the progressive nature of the geopolymerization process. The 7-day compressive strength ranged from 6.65 to 7.65 MPa, increasing to 11.25–12.75 MPa at 14 days and reaching 19.10–23.10 MPa at 28 days. Strength gain between 7 and 28 days varied from 171.69 to 230.36%, indicating substantial long-term matrix densification. Increasing NaOH molarity from 12 to 16 M improved the average 28-day compressive strength from 20.05 to 21.85 MPa, while increasing the Na2SiO3/NaOH ratio from 2.0 to 2.25 enhanced strength from 20.79 to 21.64 MPa. Similarly, raising the curing temperature from 60 to 80 °C increased the average 28-day strength from 21.03 to 21.40 MPa. The most significant improvement was observed with pond ash content, where increasing the dosage from 375 to 400 kg m−3 elevated the average 28-day strength from 20.76 to 22.70 MPa. The highest compressive strength of 23.10 MPa was achieved for the mix containing 16M NaOH, a Na2SiO3/NaOH ratio of 2.25, 80 °C curing temperature, and 400 kg m−3 pond ash content. The findings confirm that optimized alkaline activation, thermal curing, and binder dosage synergistically enhance geopolymerization, demonstrating the potential of pond ash as a sustainable precursor for structural-grade geopolymer concrete.