The study of bond strength and bond durability of reactive powder concrete

This research project aims to use reactive powder concrete, RPC, as a new repair material and evaluate its bond strength and bond durability to existing concrete. One accelerated aging environment, namely a freeze-thaw cycle acceleration deterioration test, was selected for the evaluation of bond durability of the repair materials. Before and after aging, the samples were evaluated by the compressive strength, bond strength (slant shear test), steel pull out strength, and relative dynamic modulus NDT tests. The test results show that the RPC possesses high bond strength, dynamic modulus, and bond durability as compared with other concretes. The adhesion between the RPC and the steel is also much greater than that for the other concretes. It would be interesting to verify the consequences of this improved adhesion in reinforced concrete structures. Test results revealed that RPC was still in good condition after 1000 cycles of freezing and thawing in accordance with ASTM C 666-97. After 1000 cycles, the nonshrinkage high strength mortar showed a reduction in compressive strength, slant shear strength, steel pull out strength, and dynamic modulus by 17, 21, 24, and 25 %, compared with the corresponding values of 6, 7, 5, and 10 %, respectively, for RPC. Specimens of normal strength concrete were used as reference specimens. The 5 cm × 10 cm slant shear cylinders made of normal strength concrete had deteriorated severely after 600-700 freeze-thaw cycles. For the normal strength concrete, the average values of relative dynamic modulus of elasticity based on resonant frequencies after 300 and 600 freeze-thaw cycles were 75 and 55 %, compared with the corresponding values of 96 and 92 %, respectively, for RPC.