Performance optimization of hybrid fiber concretes against acid and sulfate attack

Concrete elements used in underground structures and industrial areas are frequently exposed to acid and sulfate attacks as a result of industrial growth and climate changes. In this study, effects of different fibers, aggregates and binder types to the performance of hybrid fiber concretes against acid and sulfate attack are investigated with the help of central composite design method. Steel, glass, synthetic and propylene fibers, crushed stone and electrical arc furnace slag aggregates, fly ash and cement are hybridized each other to produce hybrid fiber concretes. Strength and mass loss of 30 different hybrid fiber concrete samples which were kept in H2SO4 and Na2SO4 solutions for 400 days, determined. Variance analysis of experimental results was performed and regression models were obtained. Steel and propylene fibers were strong against acid attack. Sulfate resistance of hybrid fiber concretes increase with contribution of steel, glass and propylene fibers. But synthetic fibers were weak both against acid and sulfate attack. Multi-objective optimization was performed to minimize the compressive strength and mass loss of the hybrid fiber concretes. Parameters for optimum concrete production are proposed as 0.04 steel fiber, 0.18% glass fiber, 0.23% synthetic fiber, 0.03% propylene fiber addition; 10.02% fly ash, 70.29% EAFS replacement and 305.41 kg/m(3) binder dosage.