Investigation of mechanical properties of concrete with clinoptilolite and silica fume using Taguchi method

To minimize the adverse impacts of cement production, introduce a natural resources as replacive cementitious material, and provide sustainable concrete, the present work identified a sub-class of zeolite soil with high SiO2 and low CaO contents, namely "clinoptilolite." It is a widely spreaded soil, mechanically active, potentially ready to contribute in concrete pozzolanic reactions in a novelty manner. The mechanical activation modified the morphology and the structure of clinoptilolite to amorphous phases (e.g., hydroxyls losing bonding strength). To approach the goals, several dosages of clinoptilolite (0-20%) with and without silica fume (0-10%) contributed to the design of 567 concrete mixes, at three water-to-binder (w/b) ratios of 0.38, 0.42, and 0.45, the mixes were cured for 7, 28 and 90 days. Using the Taguchi L9 orthogonal array, 9 sets of optimum mix designs were derived out of 27 experiments and were optimized for mechanical strength tests. The experimental data and predicted results were compared and validated with a total accuracy of 90.84% (acceptable error levels). By increasing the curing age at the lowest w/b ratio, compressive strength (up to 56 MPa), Tensile strength (up to 3.9 MPa), and flexural strength (up to 7.0 MPa) were enhanced by both replacive materials (up to 30 wt%). However, long-term development (28, 90 days) is characterized by clinoptilolite, indicating a high pozzolanic reactivity in a lower w/b ratio attributable to its specific surface area and reactive SiO2 content. The experimental program and the high accuracy of the model showed that replacing OPC with clinoptilolite and SF is highly recommended in terms of sustainable concrete production, minimizing cement manufacturing impacts, and lowering the water consumption.