Analysis of mechanical and sorptivity properties of mortar mixtures containing fly ash modified with nano-silica using the Taguchi design method

Abstract

The present study focuses on investigating the impact of four different parameters, namely, nano-silica dosage, fly ash replacement percentage, total binder quantity, and water/binder ratio, on the mechanical and durability properties of cement-based mortar mixtures modified with nano-silica. The study employs the Taguchi experimental design matrix, which enables the identification of the optimal mixture ratios that can achieve the desired properties. The orthogonal L16 design matrix is used, with four distinct levels selected for each parameter. Experiments are conducted on mortar samples produced using different mixture ratios, and the samples are tested for compressive strength, flexural strength, and sorptivity at 7th, 28th, and 90th days. The results are analyzed, and signal-to-noise ratios are obtained to determine the significance of each parameter and the optimal mixture ratios. After analyzing the results of the experiments, it was observed that the proportion of fly ash has the greatest impact on the compressive strength of the cement-based mortar on all three test days. On the other hand, the water-to-binder ratio was found to be more significant in terms of flexural strength on the 28th and 90th day. For early-age (7-day) tests, the binder volume emerged as the most important parameter. On the other hand, nano-silica played a less important role in general compared to other parameters. However, when the nano-silica and binder volume is considered, it is observed that for all three test days, nano-silica increased the compressive strength up to Level 3 (2.73%), but decreased when it reached Level 4 (4.10%). In terms of sorptivity, the water-to-binder ratio was the most significant parameter for all test days. In sum, the experiment demonstrates that different parameters have varying levels of significance depending on the mechanical and durability properties being analyzed and the duration of the tests. The best-performing mixtures are selected for further testing, and compressive, flexural and sorptivity tests are conducted again on the seventh and twenty-eighth days for confirmation. The results are compared with the Taguchi estimation results to determine the reliability of the method. Overall, the study provides valuable insights into the effects of different parameters on the mechanical and durability properties of cement-based mortar mixtures modified with nano-silica. By identifying the most significant parameters, the study provides insights that can inform the development of more effective, durable, and sustainable cement-based mixtures. The Taguchi experimental design matrix is demonstrated to be a reliable and effective method for identifying the optimal mixture ratios.