Chapter 9 - Benefits and case studies using internal curing of concrete

Proper curing of concrete is important to ensure that it achieves its intended performance and durability. Conventionally, this is achieved through external curing, applied after mixing, placing and finishing [1]. As demonstrated in the previous chapters of the present report, internal curing (IC) is potentially a very promising tool in providing additional moisture in concrete for a more effective hydration of the cement. This chapter summarizes the main benefits of internal curing and presents case studies in which those benefits could be observed in existing concrete structures.Since the 1950?s, internal curing had been inadvertently accomplished in lightweight concrete structures before its potential for reducing self-desiccation in high-performance concrete (HPC) was recognized later in the 1990?s [2]. Low-density aggregates were primarily used to reduce the mass of concrete structures. In most applications, the aggregate was saturated prior to mixing to ensure adequate workability, as it was recognized that dry porous aggregate could absorb some of the mix water during concrete fabrication and placement [3,4,5]. Lightweight concrete with a density ranging from 1440 to 1840 kg/m3 has been used in bridge decks, marine structures and other structures [6]. It was shown to achieve long-term durability from the excellent in-service performance observed in the field [7,8]. Improved cement hydration due to internal curing is one of the benefits of using lightweight concrete in structures among other benefits related to design and construction, such as: structural efficiency, seismic performance, constructability, repair, durability and economic considerations [7,9].Pour pouvoir tirer d?un b\ue9ton sa performance et sa durabilit\ue9 nominales, il est important que sa cure soit ad\ue9quate. Traditionnellement, on parvient \ue0 ce r\ue9sultat en soumettant le b\ue9ton \ue0 une cure externe, appliqu\ue9e apr\ue8s le malaxage, le coulage et le finissage. Comme il est d\ue9montr\ue9 dans les chapitres pr\ue9c\ue9dents du pr\ue9sent rapport, la cure interne repr\ue9sente un moyen potentiellement tr\ue8s prometteur de procurer au b\ue9ton une source d?humidit\ue9 additionnelle et une hydratation plus efficace du ciment qu?il contient. On r\ue9sume dans ce chapitre les principaux avantages de la cure interne et pr\ue9sente des \ue9tudes de cas dans lesquelles on a pu observer ces avantages dans des structures de b\ue9ton existantes.Depuis les ann\ue9es 1950, on r\ue9alisait en fait par inadvertance des cures internes dans des structures de b\ue9ton l\ue9g\ue8res, avant que ne soit reconnu leur potentiel dans la r\ue9duction de l?auto-dessiccation des b\ue9tons \ue0 hautes performances, dans les ann\ue9es 1990. On employait des granulats l\ue9gers essentiellement pour r\ue9duire la masse des structures de b\ue9ton. Dans la plupart des applications, on saturait le granulat avant le malaxage afin de garantir une maniabilit\ue9 ad\ue9quate du b\ue9ton frais, \ue9tant reconnu que le granulat poreux sec pouvait absorber une partie de l?eau du m\ue9lange au cours de la pr\ue9paration et du coulage du b\ue9ton. Le b\ue9ton l\ue9ger, d?une masse volumique allant de 1440 \ue0 1840 kg/m3, a \ue9t\ue9 employ\ue9 dans la construction de tabliers de pont, de structures marines et d?autres types de structures. L?excellente performance en service de ce mat\ue9riau, telle qu?observ\ue9e sur le terrain, d\ue9montre son aptitude \ue0 la durabilit\ue9 \ue0 long terme. L?am\ue9lioration de l?hydratation du ciment par la cure interne est l?un des avantages de l?utilisation du b\ue9ton l\ue9ger dans les structures; ces autres avantages, li\ue9s \ue0 la conception et \ue0 la construction, sont notamment l?efficacit\ue9 structurale, la performance parasismique, la constructibilit\ue9, ainsi que les diverses consid\ue9rations li\ue9es \ue0 la r\ue9fection, \ue0 la durabilit\ue9 et \ue0 l?\ue9conomie.Peer reviewed: NoNRC publication: Ye