Curing of Concrete

CURING OF CONCRETE

Curing is the pr0cess 0f c0ntr0lling the rate and extent 0f m0isture l0ss fr0m c0ncrete during cement hydrati0n. It may be either after it has been placed in p0siti0n (0r during the manufacture 0f c0ncrete pr0ducts), thereby pr0viding time f0r the hydrati0n 0f the cement t0 0ccur. Since the hydrati0n 0f cement d0es take time – days, and even weeks rather than h0urs – curing must be undertaken f0r a reas0nable peri0d 0f time if the c0ncrete is t0 achieve its p0tential strength and durability. Curing may als0 enc0mpass the c0ntr0l 0f temperature since this affects the rate at which cement hydrates.The curing peri0d may depend 0n the pr0perties required 0f the c0ncrete, the purp0se f0r which it is t0 be used, and the ambient c0nditi0ns, ie the temperature and relative humidity 0f the surr0unding atm0sphere. Curing is designed primarily t0 keep the c0ncrete m0ist, by preventing the l0ss 0f m0isture fr0m the c0ncrete during the peri0d in which it is gaining strength. Curing may be applied in a number 0f ways and the m0st appr0priate means 0f curing may be dictated by the site 0r the c0nstructi0n meth0d.

CURING METH0DS AND MATERIALS

C0ncrete can be kept m0ist (and in s0me cases at a fav0rable temperature) by three curing meth0ds

1. Meth0ds that maintain the presence 0f mixing watering the c0ncrete during the early hardening peri0d. These include p0nding 0r immersi0n, spraying 0rf0gging, and saturated wet c0verings. These meth0ds aff0rd s0me c00ling thr0ugh evap0rati0n, which is beneficial in h0t weather.

2. Meth0ds that reduce the l0ss 0f mixing water fr0m the surface 0f the c0ncrete. This can be d0ne by c0vering the c0ncrete with impervi0us paper 0r plastic sheets, 0r by applying membrane-f0rming curingc0mp0unds.

3. Meth0ds that accelerate strength gain by supplying heat and additi0nal m0isture t0 the c0ncrete. This is usually acc0mplished with live steam, heating c0ils, 0r electrically heated f0rms 0r pads.

The meth0d 0r c0mbinati0n 0f meth0ds ch0sen depends 0n fact0rs such as availability 0f curing materials,size, shape, and age 0f c0ncrete, pr0ducti0n facilities (in place 0r in a plant), esthetic appearance, and ec0n0mics. As a result, curing 0ften inv0lves a series 0f pr0cedures used at a particular time as the c0ncrete ages. F0r example, f0g spraying 0r plastic c0vered wet burlap can precede applicati0n 0f a curing c0mp0und. The timing 0f each pr0cedure depends 0n the degree 0f hardening 0f the c0ncrete needed t0 prevent the particular pr0cedure fr0m damaging the c0ncrete surface (ACI 308 1997).