Experimental study on the impact of traffic-induced vibrations on early-age concrete

The COUNT (Concreting under Traffic) research project systematically examined the effects of traffic-induced vibrations on early-age, hardening concrete-a critical issue for bridge construction and renovation. Traffic closures are often imposed during such projects to mitigate potential damage from vibrations. Through three methodically designed test series, COUNT identified critical vibration thresholds and underlying damage mechanisms. The vibration signals applied were both harmonic and real bridge vibrations due to the passage of cars, trucks, and trains. The first series focused on small-scale specimens of unreinforced concrete. No evidence was found that conventional traffic vibrations damage ordinary plain concrete. In the second series, concrete-reinforcement composites were subjected to artificial vibrations during hardening. These studies showed that the bond between concrete and reinforcement is weakened if vibration amplitudes are excessive. Differential displacements emerged as a more reliable damage metric than vibration velocity. The third series investigated large-scale, realistic scenarios by casting concrete slabs in direct contact with vibrating prefabricated slabs. Damage was evaluated through crack analysis, bending tests, and permeability measurements. Synthesizing results from all test series, alongside external research findings, the study provides practical recommendations for managing traffic-induced vibrations and displacements during construction. This integrated approach offers a robust framework to ensure the durability and safety of infrastructure projects while minimizing disruptions.