Discussion on the Reinforcement of Reinforced Concrete Slab Structures

Abstract

Because of global environmental changes and the continued warming of the planet, the increase in carbon dioxide emissions has had a major impact on the environment. The development of zero-carbon buildings, the promotion of energy conservation and carbon reduction, and the concept of green environmental protection are regarded as important issues for humanity to achieve sustainable development. In Taiwan, the combination of moisture and high salt content in the environment, corrosion caused by chloride ions, and earthquakes often lead to the formation of crevices in buildings. These crevices can cause rebar oxidation and corrosion and even concrete structure damage or spalling. Conventional structural damages can be repaired with epoxy resin grout. However, such practices are incapable of removing the rusted components of the rebars inside the structures and thus subject the internal rebars to continuous oxidation in the original rust-covered environment. Components located deep within the structures would still swell as a result of continuous rebar oxidation and cause concrete breaking and spalling, making previous repair efforts ineffective. This study proposes an improved repair and retrofit technique that includes the removal of rust from oxidated rebar parts, by applying low viscosity epoxy resin to the slab base and allowing it to fully penetrate the concrete cracks and surface of the rebars inside, thus producing a protective layer and repairing the bond. Additionally, carbon-fiber reinforced plastic (CFRP) patches were adopted as repair materials and attached to the beams and slab (ceiling) surfaces. Angle steels were used at the edges and installed to connect the beams to the slab with chemical anchors. The gaps between the angle steels and the slab were filled with epoxy resin grouts. On the short side of the slab, small steel H-beams were installed 1 m apart as a means of retrofit. Because the epoxy resin expands by 8% after undergoing chemical reactions, it bonds perfectly with concrete, CFRP patches, and steel materials. Approximately 10 years have elapsed since the case-study was repaired using the proposed technique, and the retrofit effect has yielded excellent results to the present day, with no occurrence of internal swelling or spalling from rebar oxidation. The proposed retrofit technique can reduce construction costs, while ensuring effective repair and maintenance of structural safety, and extend the service life of structures.

Applying Composites in Concrete Repair Engineering

“…Consequently, damage and spalling on the structures continue owing to the volume expansion of the oxidizing rebar, making future repair impossible. (7) Increasing the amount of water in a cement mix results in effective mixing and produces a cement concrete with high fluidity; however, an excessive amount of water tends to cause the formation of numerous pores within the cement stone or on the aggregate interface area, which is the major cause of poor concrete performance. Lin stated that coating recycled aggregates with a slag composite is an effective approach to improving the mechanical properties and durability of recycled concrete.…”

Surface Degradation of DGEBA Epoxy Resins Cured with Structurally Different Amine Hardeners: Effects of UV Radiation

“…Other applications of epoxy resins include coatings, sealants and adhesives, because of their outstanding adhesive properties and chemical resistance [ 25 ]. In construction, epoxy resins are applied in repairing and strengthening concrete and anticorrosion and wear-protection agents for steel structures [ 26 ]. In electronics, epoxies are used as encapsulates for LEDS and other electronic parts used in high-frequency and high-voltage applications, due to their dielectric strength and low dielectric constant, adhesives and environmentally protective coatings for printed circuit boards (PCBs).…”

Strengthening of Fibre Reinforced Concrete Elements: Synergy of the Fibres and External Sheet

“…In structural rehabilitation and strengthening, the structural members are often required to cope with larger design loading due to the upgrading of building services and facilities and heightening of design standard, while maintaining the original member size to preserve the architectural dimensions and headroom. Moreover, durability enhancement by mitigating or eliminating the reinforcement corrosion problem is often desired to extend the service life to an acceptable level [1,2]. Concrete cracking is a major initiating and accelerating factor of the corrosion of steel reinforcement.…”