Steel-concrete Bond Behaviour of Concrete Mixes with Wood Waste: Pull-out and Bending Tests of Full-Scale Beams and Columns

The present work intends to encourage a more widespread application of concrete mixes containing wood waste by investigating the steel-concrete bond of ordinary steel reinforcement bars and prestressed strands to assess the feasibility of using these composites in structural applications. After a set of preliminary tests, two mixes were selected in which aggregate was partially replaced by wood chip and sawdust. The effect of the steel-concrete bond length and reinforcement diameter on the shear strength was evaluated for steel bars and two-wire strands. The incorporation of wood appears to create a better mechanical interaction by increasing the component of friction as a resistance mechanism. In the case of the strands, the bond resistance is significantly higher (above 2.3 MPa) than the reference (0.9 MPa), regardless of the wood-concrete composites and the bond length. Additional tests have been performed to evaluate a possible creep effect. The specimens were subjected for 120 h to a constant tensile load corresponding to 50% of the mean results of the pull-out test. Results show that incorporating wood does not enhance the creep for this load level. Full-scale structural elements were also constructed to assess the feasibility of using these composites in structural applications. Bending and bending plus fatigue tests were performed to determine the behaviour under static and dynamic loads. It was concluded that the reference concrete without wood incorporation cracked for lower loads (26.0 kN) than the composites with wood (above 38.8 kN) and presented much higher bending stiffness (27835 kN.m2) than the wood-concrete composites (below 8544 kN.m2). The wood concrete with sawdust resisted fatigue tests without cracking.