Application of air cooled pipes for reduction of early age cracking risk in a massive RC wall

Abstract

The construction of massive concrete structures is often conditioned by the necessity of phasing casting operations in order to avoid excessive heat accumulation due to cement hydration. To accelerate construction and allow larger casting stages (usually increasing lift height), it is usual to adopt internal cooling strategies based on embedding water pipes into concrete, through which water is circulated to minimize temperature development. The present paper reports the use of horizontally placed ventilated prestressing ducts embedded in a massive concrete wall for the same purpose, in line with a preliminary Swedish proposal made in the 1990s. The application herein reported is a holistic approach to the problem under study, encompassing extensive laboratory characterization of the materials (including a technique developed for continuous monitoring of concrete E-modulus since casting), in situ monitoring of temperatures and strains, and 3D thermo-mechanical simulation using the finite element method. Based on the monitored/simulated results, it is concluded that the air-cooling system is feasible and can effectively reduce early cracking risk of concrete, provided adequate planning measures are taken.