Impact of aggregate properties on the development of shrinkage-induced cracking in concrete under restraint conditions

Concrete specimens were prepared with the same mixture proportion except for their constituent coarse aggregates, namely, limestone and sandstone, that possess different inherent drying shrinkage values. The strain at a cross-section perpendicular to the drying direction under restricted and unrestrained conditions was observed using a digital image correlation method. It was confirmed that initiation and propagation of cracks were greatly affected by the types of aggregate. Analysis by the rigid-body spring network method, which explicitly incorporates aggregate shrinkage and properties of the interfacial transition zone (ITZ), revealed that aggregate shrinkage and fracture energy of the ITZ greatly influence fine-crack distribution and localization of cracks. It was elucidated that pure limestone with a small drying shrinkage value can reduce the number of visible cracks in concrete under restraint conditions since it allows fine cracks to form around coarse aggregate particles that absorb the localization of cracks, thus limiting wider cracks.