Enhanced strength of portland cement products via reinforcing polypropylene/fiberglass structures obtained from a novel processing technique

An uninterrupted filament winding process was used to fabricate structures made of polypropylene and glass fiber that provide superior reinforcement to Portland cement structures. Fabricated polypropylene/fiberglass composite tubes were filled with a cement mixture and some were reinforced with internal tapes. Three‐point bending experiments, microscopic observation, and image analysis were used as tools to study various processing variables and their effect on the mechanical properties of the tubes. The temperature of the mandrel and wetting strongly affected the composite's mechanical properties. Increased temperatures diminished the void content within the composite and produced a unique “fuzzy” inner surface for the cylindrical tube. The development of this “fuzzy” inner surface improved the strength and fatigue properties of the cement filled composite tube by providing efficient load transfer to the glass fibres. Also the surface to volume ratio of the steel rebar geometry when compared to that of the polypropylene/fibreglass structure explains the superior load transfer to the glass. It was found that a tube reinforced with 15 internal tapes filled with a cement mixture recorded a maximum tensile stress of 71 MPa (10,000 psi) with excellent damage tolerance, more than a 10‐fold increase over the upper bound value for steel reinforced cement obtained from the rule of mixtures. The tube continued to be load bearing to strains of 0.4, which is more than 40 times the failure strain of glass. These large failure strains are the result of the shear yielding of polypropylene that coats the glass fibres and allows them to move within the cement.