An Experimental Study on Fracture Parameters, Mechanical Properties and Shrinkage of Lightweight Aggregate Concrete

The use of lightweight aggregates in concrete has been widely increased to reduce the weight of concrete members. On the other hand, the fracture behavior of lightweight concrete is different with that in normal concrete. Due to the limitations of conventional designing methods for concrete members, researchers and design codes have led to consider the analysis of fracture mechanics in predicting the behavior of concrete structures. In this experimental and analytical study, the fracture behavior of lightweight aggregate concrete (LWAC) is investigated on notched beams using the work of fracture method (WFM) and size effect method (SEM). Also, the mechanical properties and shrinkage of LWAC are studied. A total of 30 bending prismatic specimens and 42 compressive samples were constructed and tested to determine the fracture parameters, mechanical properties and shrinkage of LWAC. The results of experiments and analyses show that the Bazant’s size effect theory can evaluate the fracture behavior of lightweight concrete members, appropriately. The total fracture energy G_F of LWAC is by 68.1% less than that of normal concrete due to its lower load-bearing capacity. However, the initial fracture energy G_f obtained from the SEM in LWAC is approximately higher than that in normal concrete. According to the diagrams obtained from the SEM, the LWAC has more ductility and less brittleness than normal concrete. Additionally, the SEM is more accurate than the WFM to study the fracture behavior of LWAC. The use of lightweight aggregates instead of normal aggregates reduced the concrete shrinkage.