conc. curing

8/19/2019 Conc. Curing

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Concrete Curing



Topics

What is concrete curing?

Why is curing necessary?

What are the method of curingconcrete and materials to be used?

When to start curing and how long to

be cured.



Defnition o ConcreteCuring?

•

It is the process in which the concreteis protected from rapid loss of moisture at early stage and kept within a

reasonable temperature range so thatit can develop properties the mixturewas designed to achieve.



Why is CuringNecessary?

Curing is necessary for freshly cast concrete in order to

maintain the moisture as the chemical constituents in

cement react with water and heat evolves continuously

until the setting process completes.

The heat evolved during the setting of concrete is called

heat of hydration, and this heat causes the water to

evaporate. Proper and complete setting process is the

most important phenomenon that imparts the desired

strength to the concrete.



THREE KEY FACTOR FOR !RO!ERC"R#N$

% #NCE THE TREN$TH AND D"RA&#'#TY OF !RO!ERT#E OFCONCRETE ARE ET &Y THE CHE(#CA' REACT#ONOF THE )AR#O" CO(!ONENT D"R#N$ THE HYDRAT#ON !ROCE*

+* (O#T"RE % HA)#N$ "FF#C#ENT (O#T"RE TO EN"RE THEHYDRAT#ON !ROCE CONT#N"E*

,* TE(!ERAT"RE - (A#NTA#N#N$ A "FF#C#ENT TE(!ERAT"RE TOEN"RE THAT THE

CHE(#CA' REACT#ON CONT#N"E*

.* T#(E - (A#NTA#N#N$ &OTH THE (O#T"RE AND TE(!ERAT"RERE/"#RE(ENT FOR A (#N#("( !ER#OD

!ER#OD OF T#(E 0 .%1 2 DAY TO EN"RE THAT THE D"RA&#'#TY!RO!ERT#E F"''Y DE)E'O!* C"R#N$

NEED TO &E #N#T#ATED A OON A THE F#N#H#N$O!ERAT#ON ARE CO(!'ETE AND THE "RFACE W#''

NOT &E DA(A$ED &Y THE C"R#N$ O!ERAT#ON*



Curing 3etho4s an4 3ateria5 to6e use4*

- Since there is a chemical reaction betweenthe water and the cement called hydration

which increases the temperature of themix, the following methods and materialsto be used to maintain the requiredtemperature which aects the rapid

evaporation of water in the mix are asfollows!



". Water Curing 3etho4% that maintain thepresence of mixing water in the concrete

during the early hardening period. #he watercuring can be done using the followingtechniques.

- ponding or immersion

- spraying or fogging- and saturated wet covering.

#hese methods aord some cooling through

evaporation, which is bene$cial in hotweather.



Ponding or immersion - %n &at surfaces, such aspavements and &oors, concrete can be cured byponding. 'arth or sand dikes around the perimeter

of the concrete surface can retain a pond of water.



Spraying or Fogging ( )ogging andspraying with water are excellent methodsof curing when the ambient temperature is

well above free*ing and the humidity is low.



Saturated Wet Covering( )abric coverings saturated

with water, such as burlap,



. Membrane curing method + that

reduce the loss of mixing water fromthe surface of the concrete. #his canbe done by!

- covering with impervious paper

- covering with plastic sheets

- by applying membrane+formingcuring compounds.



Covering with impervious paper - -onsists of twosheets of craft paper cemented together bybituminous adhesive with $ber reinforcement, is anecient means of curing hori*ontal surfaces andstructural concrete of relatively simple shapes.



Covering with plastic sheets - /lastic sheetmaterials, such as polyethylene $lm, is a lightweight,eective moisture retarder and is easily applied tocomplex as well as simple shapes. Its application is

the same as describe for impervious paper.



Applying curing compound + 0iquid membrane+forming

compounds consisting of waxes, resins, chlorinated rubber,and other materials can be used to retard or reduceevaporation of moisture from concrete. #hey are the mostpractical and widely used method for curing not only freshlyplaced concrete but also for extending curing of concrete

after removal of forms or after initial moist curing.



When to start curing an4ho7 5ong to 6e cure4?

• -uring takes place immediately afterconcrete placing and $nishing, and

involves maintenance of desiredmoisture and temperature conditions,both at depth and near the surface,

for extended periods of times. #helength of adequate curing time isdependent on the following factors!



a. 1ixture proportions

b. Speci$ed strength

c. Si*e and shape of concrete member

d. 2mbient weather conditions

e. )uture exposure conditions

Slabs on ground 3e.g. pavements, sidewalks,parking lots, driveways, &oors, canal linings4and structural concrete 3e.g. bridge decks,

piers, columns, beams, slabs, small footings,cast+in+place walls, retaining walls4 require aminimum curing period of seven days forambient temperatures above 56 degrees

)ahrenheit.



2merican -oncrete Institute 32-I4-ommittee 76" recommends a minimumcuring period corresponding to concreteattaining 869 of the speci$ed compressivestrength. #he often speci$ed seven days

curing commonly corresponds toapproximately 869 of the speci$edcompressive strength. Similarly, longertime may be needed for dierent materialcombinations and:or lower curingtemperatures. )or this reason, 2-I-ommittee 76; recommends the following

minimum curing periods.



• 2S#1 - "<6 #ype I cement ( 8 days

• 2S#1 - "<6 #ype II cement ( "6 days

• 2S#1 - "<6 #ype III cement ( "7 days

•

2S#1 - "<6 #ype I= or = cement ( "5days

#>' '@

conc. curing

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