Study of the behavior of concrete with shrinkage reducing admixtures subjected to long-term drying

Shrinkage is a critical characteristic of concrete that can lead to undesired cracking, thereby limiting the serviceability of concrete structures. The ability to design concretes with significantly lower shrinkage is, therefore, of great practical importance. Along these lines, new shrinkage reducing chemical admixtures have been developed in order to reduce the extent of the shrinkage strains. The present work analyses the effectiveness of the incorporation of three such admixtures using long-term drying shrinkage tests. The results indicate a remarkable reduction of the shrinkage for two admixtures based on polypropylene glycol formulations while no significant improvement was obtained in the case of a wax-based admixture. Additionally, the influence of these shrinkage reducing admixtures on other basic properties of the concrete, such as workability and 28-day compressive strength, has been quantified. A plasticizing effect, which can be exploited for reducing the superplasticizer dosage or the water/cement ratio, was observed in the case of the two glycol-based admixtures. A slight decrease of the compressive strength was measured in all the cases due to the incorporation of the admixtures.