DESIGN OF FIBER-REINFORCED DSP MIXES FOR MINIMUM BRITTLENESS

The limitations of the traditional material design approach in driving properties to extreme values and handling multiple design criteria an d variables can be overcome by applying the optimization approach. Fib er-reinforced cement based composites based on strong aggregates and e xhibiting approximately bilinear fiber pullout behavior are optimized in the present study for a given compressive strength f'(c) with a vie w to maximising their uniaxial tensile strength F'(t) and fracture ene rgy G(F). Relations for the bridging stresses prior to and during fibe r pullout are established using fracture mechanics. The mix design lea ds to nonlinear single, or multicriterion maximization problems for th e objective functions f'(t) and l(ch) = EG(F)/f'(2)(t) (characteristic length), subject to an equality constraint on f'(c). In this way, opt imal values for the microstructural parameters (fracture toughness of paste, length of fiber, and volume fractions and diameters of aggregat e and fiber) are obtained. (C) 1998 Elsevier Science Ltd.