Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing Advanced concrete technology3 curing
Curing Bryan Marsh ~ ~i~i~i~ ~iii ¸¸ The aim of this chapter is to examine when and why curing of in-situ concrete is necessary and what effect curing has on its hardened properties A typical definition of curing (BS 8110, 1997) is 'the process of preventing the loss of moisture from the concrete whilst maintaining a satisfactory temperature regime' This particular definition adds that the curing regime should prevent the development of hightemperature gradients within the concrete Many other definitions exist which include references to hydration, durability and cost but there are three basic elements to consider: • Moisture • Heat • Time According to the British Standard for the structural use of concrete, BS 8110 (1997), the intention of curing is to protect concrete against: 3/2 Curing • • • • • • premature drying out, particularly by solar radiation and wind (plastic shrinkage) leaching out by rain and flowing water rapid cooling during the first few days after placing high intemal thermal gradients low temperature or frost vibration and impact which may disrupt the concrete and interfere with bond to reinforcement Adequate curing will facilitate, but not necessarily ensure, the optimal development of the surface zone of fresh, newly cast concrete into strong, impermeable, crack-free and durable-hardened concrete The objective is to keep the concrete saturated, or as near saturated as possible, for sufficient time for the original water-filled space to become filled to the desired extent by cement hydration products According to the research reviewed in CIRIA (1997), the depth of the surface zone directly affected by curing can be up to 20 mm in temperate climatic conditions, and up to 50 mm in more extreme arid conditions Properties of the concrete beyond this zone are unlikely to be affected significantly by normal curing It is, however, this surface zone that is often relied upon to provide many of the essential requisites of a concrete structure or element such as abrasion and chemical resistance and protection of embedded reinforcement Figure 3.1 shows the relative depths from the surface at which various properties will be affected by inadequate curing The importance of appropriate curing must therefore not be overlooked Weathering Concrete surface ,/ z~ ,4 Abrasion ,4 A z~ ,4