PERFORMANCE OF POLYPROPYLENE FIBERS AND SILICA FUME CONCRETE FOR BRIDGE OVERLAYS

摘要

Silica fume has been successfully used in concrete bridge overlays to impede moisture andchloride ingress thus minimizing corrosion problems. Laboratory and field work both show thatsilica fume concrete is particularly sensitive to curing. Polypropylene fibers have beenconsidered to minimize potential cracking and to enhance the overall concrete performance.However, there is a scarce data regarding the interaction of the two constituents and applicatorsoften seek recommendations pertinent to the types and dosages to be incorporated.This document presents the major part of a larger scale investigation that aims at achieving betterunderstanding of silica fume and polypropylene fibers interaction. The work herein focuses onthe short and long term properties of concrete that can be implemented in bridge overlays. Tomeet the study goals, twenty-four mixtures were prepared and sets of fresh concrete, hardenedconcrete tests were performed. Chemical durability, permeability and cracking pattern wereevaluated in various environments.Results reveal that silica fume/polypropylene concrete is highly influenced by the dosages ofboth ingredients. Both fibers and silica fume result in a slump reduction while the silica fumeand low water to cementitious ratio are the two major contributors to compressive strengthincrease. The fibers examined had minor contribution to flexural strength. Upon adequate silicafume and fibers, the composite can yield low permeability, minimized cracking and goodchemical soundness.