Utilizzo del cemento cellulare per la costruzione di banchine laterali a rottura programmata per l'arresto in sicurezza dei veicoli

Road safety is, nowadays, one of the most important aspects related to the design of a new infrastructure or the enhancement of existing ones. Safety devices are generally used against veer-off alongside of the road platform; usually they are iron or cement concrete barriers. However, in many foreign countries, since many years, devices are used which are called arrestor beds; these have the function to slow down in total safety a vehicle out of control, causing on it the less possible damages. Those devices, composed of a bed of gravel (of adequate shape and dimension), disposed parallel to the roadway and adjacent to it, even if contribute undeniably to the safety of the infrastructure, present many problems due to the scattering of the gravel on the carriageway in case of an accident. In order to prevent these problems, the possibility to realise arrestor beds made of cellular cement concrete has been analysed. The proposed material presents mechanical and deformative characteristics very peculiar, because an initial plastic deformation is followed by a gradual and progressive fracture. This particular characteristics allow to slow down a vehicle in total safety because the energy needed for the plastic deformation and the following fracture is obtained on the worth of the kinetic energy of the vehicle that goes through it. Accordingly to it, the characteristics of the cellular cement concrete have to be adequately planned and tested during the production of the material. The paper describes a characterisation study of different types of hydraulical mixtures for arrestor beds, made by different aggregates (siliceous sand, rubber grit, foundry sands). Many tests were carried out on the concrete in order to identify its most interesting mechanical properties: compressive strength, dynamic modulus and indirect tensile stress test. Furthermore, some dynamic tests have been planned to be carried out with in-scale experiments. This study has lead to the creation of a protocol to use for the evaluation of the characteristic of the material during the production phase.