Compaction of porous materials under dynamic loading: A comparison of the 𝑝 − 𝛼 and 𝜀 − 𝛼 model for concrete and concrete-like materials

This work investigates the compaction behavior of concrete and adobe considering its porosity under dynamic loading. Two evolution equations for the porosity, the 𝑝 − 𝛼 and the 𝜀 − 𝛼 model, are detailed and compared. The 𝑝−𝛼 model is well established in conjunction with the RHT model for concrete and parameter for different concrete grades are available. Unfortunately, the model describes the porosity as a function of the pressure, rendering the formulation implicit with accompanying high computational costs in explicit time integration schemes. In contrast, the 𝜀−𝛼 model offers a simplified approach by linking porosity to the volumetric strain, a measure which is known at the beginning of an integration cycle. This model has found wide spread in the geological community where astronomical problems are of interest, but has not yet been applied to construction materials. We compare standard single element compaction paths as well as high dynamic planar plate impact tests for concrete and derive parameter sets for the 𝜀 − 𝛼 model, which yield almost identical results as the 𝑝 − 𝛼 model. Computational efforts are reduced; however, limitations in the choice of the parameters make the model in rare cases less flexible compared to the 𝑝 − 𝛼 description.