A load induced thermal strain (LITS) semi-empirical model for plain and steel fiber reinforced concrete subjected to uniaxial compressive load

A Load Induced Thermal Strain (LITS) semi-empirical model for plain and steel fiber reinforced concrete is proposed, assuming concrete as a heterogeneous 2-phase (matrix + aggregates) material. The effects of dehydration creep and the geomechanical properties decay of the coarse aggregates are taken into account separately in the model by independent parameters calibrated on the basis of the main results on plain concrete available in the scientific literature. The role of the coarse aggregates and the cement content are investigated. It was noticed that the amount of coarse aggregates is directly proportional to LITS, with a logarithmic variation. A comparison between the results of the model with experimental tests in literature, considering different types of concretes (conventional, high strength and ultra-high performance), demonstrated the reliability of the proposed model. Moreover, the model was compared with experimental tests in uniaxial compression on Steel Fiber Reinforced Concrete (SFRC) cylinders with 11-years-old, showing a reasonable approximation. The effect of concrete aging to LITS is also investigated. It is demonstrated that concrete aging is responsible for the reduction of LITS. A reduction factor beta(t(0)) was defined on the basis of a set of experimental values ranging between 28 days and 11 years.