ENGINEERING PROPERTIES OF EPOXY RESINS USED AS CONCRETE ADHESIVES

Some mechanical properties of two commercial bulk-hardened epoxy adhesives were examined to update and complement existing data on these materials. Results revealed that cured epoxy adhesives possess higher tensile and shear strength than portland cement concrete and much-reduced Young's and shear moduli. The influence of curing temperature on the mechanical strength of the material was studied by testing the strength of epoxies after curing at temperatures of 10, 20, and 40 deg C. Long-term tensile creep tests of epoxy adhesives subjected to different sustained stresses that were conducted indicated that bulk-hardened epoxies have creep strains of less than 0.04. Long-term water resistance of concrete-to-concrete adhesion joints was investigated by comparing bond strength after 135 days of water immersion with control samples. Tests showed that the effect of water on adhesion joints was significant. Long-term water absorption of epoxies that was measured revealed that cured epoxies possess long-term water absorption values between 1.2 and 1.4 percent. Bond strength of hardened-to-hardened concrete and hardened-to-wet concrete adhesion joints subjected to different curing times and temperatures were determined using a slant shear test. The bond strength of concrete-to-concrete joints made with these epoxies generally exceeded 10 Mpa at 23-25 deg C and the effect of curing temperature and time on bond strengths was notable. Pullout tests to determine epoxy adhesion joints between portland cement concrete and deformed steel bars were also conducted and theoretical maximum adhesive bond stress, apparent adhesive bond stress, and pullout load-deformation were calculated. Results showed that the epoxies tested possess high pullout resistance and the higher deformation of the adhesive layers benefits concrete-to-epoxy-to-steel adhesion.