The Role of Silica Fume in Enhancing the Strength and Transport Properties of PET Fiber–Ultra High-Performance Concrete

The influence of varying contents of supplementary cementitious material, namely silica fume (SF), on the transport properties of ultra-high performance concrete containing polyethylene therephthalate (PET) fibers under a steam curing regime has been investigated in this study. SF was used as a supplementary binder as a partial replacement of the ordinary portland cement (OPC) in different proportions (5, 10, 15, 20, 25, 30, and 35 %), whereas shredded waste plastic PET bottles were used as fiber reinforcements at 1 % of the total mass binder to produce ultra high performance PET reinforced concrete (UHPPRC). The presence of SF between (5 % and 30 %) in UHPPRC increases compressive strength at all ages of 3, 7, and 28 days; the greatest compressive strength achieved was 146.6 MPa by the SF25-UHPPRC mix, but the compressive strength reduced at higher SF contents, in particular for the SF35-UHPPRC. Besides, the SF inclusion improved the transport properties of PET-fiberized concrete. The greatest improvement was seen with SF25-UHPPRC, which showed increases of 75.2 % in porosity, 92.6 % in water permeability, and 95.8 % in rapid chloride permeability relative to the control mix at 28 days. This could indicate that the incorporation of SF and PET fiber increases the possibility of using PET fibers in the production of ultra-high performance PET fiber reinforced concrete with superior engineering and transport properties.