Reduction of shrinkage deformations of the road concrete by the use of novel shrinkage reducers

Report date: 14.12.2017

Concrete pavements are subjected not only to traffic loads but also to load-independent effects. In addition to thermal deformations, these include above all shrinkage deformations. If the resulting constraining stresses exceed the tensile strength of the concrete, cracking may occur. For this reason, joints are generally arranged at intervals of around 5 m to effectively reduce the constraining stresses. For some time now, so-called shrinkage reducers (SRA) have been available to reduce the constraining stresses due to shrinkage deformations, by means of which both the shrinkage deformations at a young age and the drying shrinkage can be reduced. The aim was to determine the extent to which shrinkage deformations and thus potential cracks can be effectively reduced by SRA. To this end, shrinkage tests were to be carried out both on the fresh / hardening concrete and on the hardened concrete at a later age. In addition, the extent to which the fresh and hardened concrete properties are potentially influenced also had to be investigated. The investigations showed that SRA can, in particular, reduce the shrinkage deformations that occur at an early stage. This has a particularly positive effect on the prevention of early shrinkage cracks in the first days. Shrinkage reduction was generally always greater in the initial phase and decreased after 187 days to values between 30 and 50%. The extent to which drying shrinkage, which takes place over a period of years, is reduced cannot be deduced from these investigations, which extend to only 6 months. The fresh concrete properties were not affected by the SRA. Likewise, no significant changes in compressive strength, splitting tensile strength and static modulus of elasticity were found. On the other hand, it was found that the microair pore system in concretes with high freeze-thaw resistance can be adversely affected by the addition of glycol- and polyglycol-based SRA.