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Reduction of Early-Age Crack Risks in Concrete Walls by Using a New Casting Technique

Abstract Volumetric changes in early-age concrete that are restrained might lead to cracks. The degree of restraint is influenced by the casting sequence and the dimensions of the castings. In the current study, a new casting technique is proposed to reduce the restraint in newly cast concrete by following a new method of arranging the structural joint with the existing old concrete. The proposed technique is valid for the typical wall-on-slab structure using one structural joint. According to this casting method the lower part of the wall is cast together with the slab, which is called a kicker. Thereafter, the behaviour of the structure changes from a typical wall-on-slab case to a typical wall-on-wall case. It has been proven based on the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall by using the kickers. In this paper, different kicker heights are studied with the aim of determining the minimum restraint in the upper part of the wall cast in contact with the kicker. The technique using kickers is compared with common measures used in the field to avoid cracking, such as using cooling pipes in the new casting and/or heating cables in the adjoining old concrete. The presented method is both cost and time effective, as it opens up the possibility to use larger structural length for each casting sequence.