Flexural performance of damaged RC beams strengthened with carbon-, glass-, and steel-fibre-reinforced ferrocement systems

Ferrocement strengthening of reinforced concrete (RC) beams is an effective rehabilitation technique; however, the brittleness of plain mortar and inadequate stress transfer between the mortar, steel mesh, and parent concrete can limit its effectiveness. Although steel fibres provide significant benefits, their susceptibility to corrosion may reduce durability in aggressive environments. To address this issue, this study investigated 15 damaged small-size RC beams strengthened with ferrocement jackets using unreinforced mortar (URM) and mortar incorporating 0.25%, 0.5%, and 1% carbon fibre (CF) and glass fibre (GF) by volume of mortar. For comparison, four additional beams were strengthened using 0.5% and 1% steel fibre (SF). The performance of the strengthened beams was compared with that of four unstrengthened control beams (USBs). In addition, the compressive strength, flexural strength, porosity, and shrinkage properties of the corresponding mortars were evaluated. The results demonstrated significant improvements in the load-deflection behaviour of the strengthened beams. The ultimate load increased by 53% for the URM ferrocement system, 83–100% for CF, 56–86% for GF, and 102–103% for SF compared with the USBs. All fibre-reinforced systems exhibited enhanced post-cracking behaviour and deformation capacity. The flexural strength of the mortar increased by 4–42%, while compressive strength increased by 3–74% for the GF and SF mixes; however, CF reduced compressive strength with increasing fibre content. Fibre incorporation also significantly reduced drying shrinkage despite generally increasing porosity. The results demonstrate that CF and GF can be effectively incorporated into ferrocement strengthening systems to enhance the flexural performance of damaged RC beams while offering the potential advantage of corrosion resistance over conventional steel fibres.