Performance Research Of Inorganic Adhesive Material In Reinforced Concrete Structure

At present, epoxy is widely used as structural adhesive glue. But there exist many disadvantages of it, like lower softening point, bad thermal stability and poor fatigue resistance, makes the FRP cloth can't play well. Therefore, we need to produce a adhesive with better compatibility and better performance to promote the affection of FRP composite materials when they are used in repairing and reinforcing concrete structures. MPC(Magnesium Phosphate Cementitious) has many good properties:â—‹1 Curdling and stiffening rapidly;â—‹2 High early strength;â—‹3 Fast condensation in low-temperature;â—‹4 high bonding strength with the old concrete;â—‹5 Well wear resistance and good frost resistance,little shrinkage. This project is working on researching the properties of MPC when use it reinforcing concrete, mainly tests and results as below:(1) MPC usually made by ADP (Ammonium Dihydrogen Phosphate) as Phosphate raw material, the reaction will consist with ammonia, bringing peculiar smell and polluting the surroundings. So this project changes raw material from ADP to Potassium Dihydrogen Phosphate Disodium hydrogen phosphate. Thinking about the needs of reinforcement construction conditions, the ratio of raw materials must fulfill the requirements of MPC products as fluidity of 200mm and initial setting time of 30 min. This project worked out four rational ratio of raw materials by adjusting the ratio of MgO and KH2PO4, water-cement ratio, and the content of fly ash and retarder.(2) After the tests of mortar compressive and mortar flexural of MPC, the three point bending tests of mortar test blocks and the splitting test of concrete blocks after bonding by MPC, analyzing the strength and failure mode of there 4 ratio of raw materials. And then choose the better one and put them into reinforcement test. Meanwhile choose the best one to test the effective bond length, and found it between 150mm and 180mm.(3) Found out the MPC reinforcement's failure mode is good, through the tests of reinforcement of prism beams and columns. When it used as the base of basalt FRP reinforcement, the increased modulus of bending strength for plain concrete beams showed by four-point bending test could be 57.5%; the increased modulus of ultimate axial for columns showed by axial compression test could be 45.4%.(4) Put beams which reinforced by MPC into the oven 240min with the temperature of 100 o C, and take other three groups (EP reinforced beams, beams which are reinforced by EP first and then brush MPC on the surfaces, nude beams) as compare. Then take the test of four-point bending and found out the bending strength as below: Ep's increased modulus is 50%, just as the half under normal conditions; MPC's (P3-B10) increased modulus is 57.5%. Because of the declination of strength happened on beams selves, though the affection of reinforcement isn't obvious, it still has improvement spaces, and better than EP under high temperature.