Longitudinal restraining devices for the evaluation of structural behaviour of cement-based materials: The past, present and prospective trends

The problem of thermal and shrinkage cracking in concrete has been long recognised by researchers and engineers as it can jeopardise the intended serviceability of a concrete structure. This has led researchers to develop testing devices which aim to simulate the behaviour of concrete under restrained deformations. Such devices are discerned in passive and active, depending on how concrete's movement is restrained, whilst a new type of devices has been developed to account for the combined effects of intrinsic restrained deformations and externally imposed actions. This paper presents a detailed and critical literature review on the developed restraining devices and an analysis of the capabilities, complexities and peculiarities associated with their use. Further to this, the challenges the developers of testing devices are faced with, the gaps and uncertainties with the methods found in the literature and recommendations for potential improvements in the field are discussed.