Experimental and simplified visual study to clarify the role of aggregate–paste interface on the early age shrinkage and creep of high-performance concrete

An experimental study and visual analysis were carried out to indicate the effect of pre-saturated coarse lightweight aggregate on the mechanical properties, the early age shrinkage and creep of high-performance concrete from 7 to 50 days. Even though the results showed that the utilization of lightweight aggregate (LWA) in the concrete mixtures caused a reduction in mechanical strength; it improved concrete performance against creep and shrinkage compared with those for the normal ones. A simplified visual method based on image processing with no sample preparation was employed to compare the aggregate–paste interface during creep and shrinkage tests. The image analysis could clarify the thicker interface of paste around LWAs in comparison with normal aggregates. Likewise, the images showed the distinguishable border around normal aggregate. This border was considered the most vulnerable region for cracking during the mechanical tests.