Research of electrochemical chloride extraction and reinforcement of concrete column using MPC-bonded carbon fiber reinforced plastic sheet & mesh

Magnesium phosphate cement (MPC) is used as an adhesive that bonds carbon fiber reinforced plastic sheet (CFRP sheet-Cs) and mesh (CFRP mesh-Cm) in formation of the MPC-CFRP composite material. This type of MPC-CFRP composite material can serve as both an anode, Cs and Cm electrodes, for extracting chloride ions and a reinforcement material for concrete columns, and it contributes to bearing capacity improvement and electrochemical chloride extraction (ECE) of concrete structures. Compared with the traditional Ti-RuO2 anode (T electrode), the MPC-CFRP composite material is used to strengthen concrete columns and extract chloride ions. Current density, i = 4, 8 A/m2, and power-on time, t = 14, 28, 42 d, are considered to illuminate the effect of the ECE system on the axial compressive strength, chloride ion concentration and bond strength of the rebar-concrete interface of concrete columns. Cs and Cm electrodes can be used as anodes of the ECE system to migrate chloride ions near the rebar effectively toward the concrete surface. The increase of power-on time and current density improves the chloride extraction efficiency. Cs electrode has similar chloride extraction efficiency as T electrode under the same experimental condition superior to Cm electrode. The bond strength of the rebar-concrete interface degrades after ECE and the degradation increases as the current density and power-on time increases. Cs and Cm electrodes significantly improves the bearing capacity and ultimate displacement of concrete columns. However, the strengthening effect decreases as the current density and power-on time increases. The mechanical properties of the strengthened concrete columns are still superior than those of the un-strengthened. Cs and Cm electrodes can achieve the dual effects of reinforcing and repairing reinforced concrete structures. The estimated equations of ECE efficiency and ultimate load of concrete columns agree with the test data.