Current research status of UHPC creep properties and the corresponding applications – A review

Ultra-high performance concrete (UHPC) has super high strength, ductile behavior, and excellent durability, which is quite different from conventional concrete. Many aspects of UHPC (mixture design, mechanical properties, shrinkage behavior, engineering applications, etc.) have been widely investigated. However, the information about creep properties of UHPC is not sufficient, which is vital to engineers for safe structure design as well as for predicting the structure's long-term performance. Thus, this study systematically brings together the published research on UHPC creep behavior, and major contents are as follows: 1) introduce basic terms for UHPC creep and give comparisons with conventional concrete; 2) summarize the various influencing factors on UHPC creep (curing regime, loading age, stress level, load type, w/b, fibers, mixture compositions, humidity, specimen size, etc.); 3) explain the mechanism of UHPC creep, relaxation performance, creep prediction models or equations in specifications; 4) give engineering applications considering UHPC creep (long-term deformation, prestress loss, early-age restrained stress, etc.); 5) summarize creep coefficient data from literature and propose future perspectives. This review can give researchers and designers a comprehensive and better understanding of UHPC creep, and facilitate the development of safe provisions for UHPC structures considering creep effect.