Local bond properties of steel rebar embedded in poured earth concrete: effect of recycled fine aggregate and rebar diameter

The use of poured earth concrete (PEC) as a sustainable alternative to traditional concrete has been gaining popularity. However, there are challenges with the interfacial properties between rebar and concrete, and no research is dedicated to addressing this issue. Accordingly, an experimental program is conducted in the present study to measure the bond properties in PEC. Various rebar diameters of 14 mm, 18 mm, and 25 mm are considered. Different fine aggregate replacement percentages by recycled aggregate (RA) are also selected to improve PEC's sustainability, including 30%, 50%, and 100%. A constant effective water-to-binder ratio of 0.50 is chosen. Various local bond characteristics are measured from the bond-slip envelope curves, including average bond stress, bond strength, residual bond stress, and bond energy. Results show that despite the low strength, appropriate bond properties along with pull-out failure mode can be obtained for PEC samples. Increasing rebar diameter considerably reduces the bond properties of PEC specimens and causes splitting failure mode. Higher contents of RA result in a reduction in bond properties, so that 30% fine aggregate replacement is the optimum content of RA. A new bond-predicting model is also proposed in the present study for PEC samples containing RA.