Statistical Models to Optimize Fiber-Reinforced Dune Sand Concrete

Abstract

Flexural strength and toughness of dune sand concrete (DSC) can be improved by reducing the water-to-cement ratio, adding fillers to improve the compactness of the matrix, or incorporating steel fibers. The incorporation of fibers and fillers can increase the viscosity and yield stress and necessitates higher dosage of high-range water-reducer to maintain the desired fluidity. The mixture proportioning of DSC involves tailoring several parameters to achieve adequate fresh and mechanical properties. The optimization procedure of DSC reinforced with steel fibers often necessitates several trial batches before establishing optimal balance among the various mixture parameters that affect workability and mechanical properties of concrete. DSC proportioned with 0.46–0.73 w/c ratio, 65–335 kg/m3 of limestone filler, and 0–108 kg/m3steel fiber was evaluated. The study was undertaken to model the influence of w/c, limestone filler, and fiber contents on air content, plastic viscosity, compressive and flexural strength characteristics of the DSC. Experimental test results showed that the incorporation of 94.5 kg/m3 of fiber resulted in a significant improvement in flexural strength (up to 11.5 MPa). Statistical models established using a central composite design indicate that the w/c has the greatest effect on air content, plastic viscosity, and compressive strength of DSC than limestone filler and fiber. However, the fiber is shown to have the greatest effect on flexural strength. The established models showed that the use of limestone filler can compensate for the reduction in compressive and flexural strengths due to the increase in w/c. Trade-off between w/c, limestone filler content, and fiber dosage to optimize mixture proportioning to enhance the mechanical properties of DSC without adversely affecting fluidity is discussed.