Numerical study on shrinkage cracking of concrete slabs-on-grade

Industrial pavements are thin slabs on a continuous support subjected to restrained shrinkage and point loads. Shrinkage cracking and upward slab edge curling are common causes of cracking. The use of fibers as an alternative reinforcement to steel welded wire mesh and rebars is today an extensive practice for the reinforcement of concrete slab-on-grade. The post-cracking performance provided by glass macro-fibers at low crack openings is particularly convenient in structures with a high degree of redundancy, such as slabs on grade, where the ultimate bearing capacity involves very low crack openings (usually below 0.3 mm). Referring to service conditions, it is well known that concrete shrinkage as well as thermal effects tend to be the principal reasons for the initial crack formation in slabs on grade, since these elements present large size, low thickness and high degree of restraint. A numerical study on the risk of cracking due to shrinkage in slabs on grade is presented herein. Special attention was devoted to the evaluation of the beneficial effects of glass fibers in controlling cracking phenomena due to shrinkage. The numerical analyses were carried out by considering different size of slabs. Since shrinkage stresses in slabs on grade are considerably influenced by external constraints which limit the contractions, different sub-grade conditions have been considered