Variability and Probability Distribution Analysis of Geopolymer Concrete Using Response Surface Method

Geopolymer concrete, with its waste-reutilization property and reduction in carbon footprint relative to conventional concrete, combined with high-mechanical properties, has gained very broad recognition during the last few years. In real-life applications, however, there exists some variation in its mechanical properties, which has a direct impact on the structural safety and reliability. Thus, there is a strong need to thoroughly explore this variability in performance and its implications for the structure. This paper has used response surface methodology to explore the influence of three factors, namely fly ash to binder ratio, aggregate to binder ratio, and water to binder ratio (W/B). Mix proportions had been developed to 13 mixes, and 260 specimens were tested in compressive strength, splitting tensile strength, elastic modulus, and slump. There were statistical properties calculated. The findings have shown that the effect of W/B on the coefficient of variation (COV) of compressive and splitting tensile strength is a significant one. W/B below 0.45 indicates that the COV of compressive and splitting tensile strengths is kept at a low level of 0.05–0.08. Nevertheless, at W/B above 0.48, the COV is so high as above 0.15. Through statistical testing, the compressive strength was found to be normally distributed (p = 0.0585, μ = 0.9800, σ = 0.572) and this is consistent with the normal distribution general structure of ordinary Portland cement concrete and the splitting tensile strength was found to be of a Weibull distribution (p = 0.6673, μ = 0.9427, σ = 0.1678), which reflects the standard deviation of the strength pattern and brittle nature of the material when it is subjected to a tensile load.