A Novel Durability Based Concrete Mix Design Using Supplementary Cementitious Materials and Modified Aggregate Band Gradation

This study focuses on proposing a novel mix design method giving emphasis to the durability of concrete and replacing cement with supplementary cementitious materials (SCMs) at certain percentages. It also includes band gradation of aggregate that merges fine and coarse aggregates to result in a single well-packed combined gradation. Two replacement levels (20% and 35%) of fly ash and three replacement percentages (20%, 65% and 90%) of slag by weight of cement were used to prepare a significant number of concrete mixes. Compressive strength, workability and durability of the prepared mixes were determined. Rapid Chloride Permeability Test (RCPT) was carried out for measuring durability of concrete. From the prepared mixes, it was possible to achieve 90-day RCPT value as low as 216-coulomb and 28-day compressive strength up to 46.5 MPa. Several contour plots were developed correlating the three mix design parameters (compressive strength, slump and durability) with cement and water contents. Finally, using the plotted contours, a mix design process has been organized into five simple steps that can easily be followed in order to proportion an optimized ratio of cement, aggregate and SCMs for preparing durable and economical concrete mixes.