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    Concrete Curing

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    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.

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    Defnition o Concrete Curing?

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

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

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    Why is Curing Necessary?

    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.

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    THREE KEY FACTOR FOR !RO!ER C"R#N$

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

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

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

    CHE(#CA' REACT#ON CONT#N"E*

    .* T#(E - (A#NTA#N#N$ &OTH THE (O#T"RE AND TE(!ERAT"RE RE/"#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*

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     Curing 3etho4s an4 3ateria5 to 6e use4*

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

    which increases the temperature of themix, the following methods and materials to be used to maintain the required temperature which aects the rapid

    evaporation of water in the mix are as follows!

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

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

    -  ponding or immersion

    - spraying or fogging - and saturated wet covering.

     #hese methods aord some cooling through

    evaporation, which is bene$cial in hot weather.

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

    of the concrete surface can retain a pond of water.

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    Spraying or Fogging ( )ogging and spraying with water are excellent methods of curing when the ambient temperature is

    well above free*ing and the humidity is low.

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    Saturated Wet Covering ( )abric coverings saturated

    with water, such as burlap,

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    . Membrane curing method + that

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

    - covering with impervious paper

    - covering with plastic sheets

    - by applying membrane+forming curing compounds.

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    Covering with impervious paper - -onsists of two sheets of craft paper cemented together by bituminous adhesive with $ber reinforcement, is an ecient means of curing hori*ontal surfaces and structural concrete of relatively simple shapes.

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    Covering with plastic sheets - /lastic sheet materials, such as polyethylene $lm, is a lightweight, eective moisture retarder and is easily applied to complex as well as simple shapes. Its application is

    the same as describe for impervious paper.

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     Applying curing compound + 0iquid membrane+forming compounds consisting of waxes, resins, chlorinated rubber, and other materials can be used to retard or reduce evaporation of moisture from concrete. #hey are the most practical and widely used method for curing not only freshly placed concrete but also for extending curing of concrete

    after removal of forms or after initial moist curing.

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    When to start curing an4 ho7 5ong to 6e cure4?

    • -uring takes place immediately after concrete placing and $nishing, and

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

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

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    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 linings4 and structural concrete 3e.g. bridge decks,

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

    )ahrenheit.

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    2merican -oncrete Institute 32-I4 -ommittee 76" recommends a minimum curing period corresponding to concrete attaining 869 of the speci$ed compressive strength. #he often speci$ed seven days

    curing commonly corresponds to approximately 869 of the speci$ed compressive strength. Similarly, longer time may be needed for dierent material combinations and:or lower curing temperatures. )or this reason, 2-I -ommittee 76; recommends the following

    minimum curing periods.

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    • 2S#1 - "' '@

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