High temperature resistance of reinforced concrete beams strengthened with steel reinforced inorganic polymer (SRIP)

Use of Fiber Reinforced Polymer (FRP) composite in infrastructures has steadily increased over the last two decades. The primary use is still for repair, rehabilitation and strengthening of structural elements made of reinforced or prestressed concrete. FRP has substantial advantage over classical structural materials such as steel in the area weight, strength, and durability against corrosion. Two major drawbacks of FRP are the lack of fiber resistance and brittle fracture of high strength fibers. The results presented in this dissertation address these two issues. High strength steel wire, commercially known as “Hardwire,” was used in combination with inorganic matrix. The inorganic matrix, similar in chemistry to Portland cement matrix, is more compatible with steel than organic polymers. In addition, the matrix can withstand more than 2000°F with no smoke, or toxins. The larger fiber diameter, as compared to thin carbon or other high strength fibers, and non-simultaneous failure of wires provide better ductility as compared to classical FRP. The experimental and analytical investigations were tailored to evaluate steel reinforced inorganic polymer (SRiP) composite at high temperatures. Rectangular reinforced concrete beams strengthened with SRiP on the tension side were tested with high moment section exposed to temperatures upwards of 1000°F. The beams were loaded in four point loading, and the maximum moment section at the midspan was heated using hot plates. Heating and cooling were repeated three times to establish the robustness of the repair at high temperature. After this cyclic exposure, Beams were tested to failure. Control beams with no strengthening and control strengthened beams that were not exposed to high temperature were also tested to compare the behavior of SRiP beams with carbon FRP strengthened beams. The results show that SRiP strengthened beams behaved similarly to classical FRP strengthened beams and can withstand higher temperatures without losing load capacity. Note that most polymers cannot withstand more than 300°F and carbon fibers start to oxidize around 800°F. Overall results presented in the dissertation show that inorganic polymer-steel fiber, high strength composite is a viable FRP for strengthening and rehabilitation. The added advantages are high temperature resistance and improved ductility.Ph.D.Includes bibliographical referencesby Daniel Gre