Evaluation of bonding performance of ultra high-performance concrete with fly ash content as overlay on normal strength concrete.

Ultra High-Performance Concrete (UHPC) has good mechanical strength and durability, so it can be the solution for an overlay material for old materials that need to be renewed. The problem with using UHPC as a construction material is the high price and sustainability, so a partial replacement for cement is required to reduce production costs, energy consumption, and CO2 gas emissions. Bonding performance is an important parameter and must be considered when applying UHPC as an overlay material. The bonding performance test of the UHPC consists of three tests: the slant shear test, splitting tensile, and direct tensile/pull-off test. The results of this study were compared with the standards of ACI 546R-14 and M.M. Sprinkel & C. Ozyildirim. Based on the test results, replacing 40% of cement with fly ash on UHPC is good to use as an overlay because it meets applicable standards. The test results showed an increase of 27% in the slant shear test and 37% in the splitting tensile test compared to the existing standard. Replacing cement with fly ash in UHPC can also increase workability, reducing the need for superplasticizers, reducing UHPC production costs by 18.4%, energy consumption, and CO2 emission problems