Proposing an Image Analysis to Study the Effect of Lightweight Aggregate on Shrinkage and Creep of Concrete

Creep and shrinkage, particularly in lightweight concrete, are known as complex phenomena that highly affect the serviceability of concrete. This may be due to the fact that creep and shrinkage behaviors are highly dependent on the behavior of the surface layer at the interfacial transition zone of the aggregate and surrounded cement paste. Despite the importance of the influence of creep and shrinkage on concrete behavior, however, no simple measuring methods were accepted by researchers until now. In the present article, the shrinkage and creep of both normal and lightweight concrete, made by expanded clay, were studied via image analysis and traditional methods. A load control system equipped with a camera was designed to measure the strains of the cured specimens induced by shrinkage and creep. The water/cement ratio was 0.3. The results were also verified by direct measuring via embedded strain gages on the concrete surface. Both measuring methods showed that the expanded clay improved the transition zone of the lightweight specimens, and the induced creep and shrinkage strains of the lightweight specimens were smaller than those for normal specimens. Lower creep and shrinkage values were obtained by a visual measuring method rather than by direct measuring methods.