MATURITY of CONCRETE

 👉 The strength of concrete depends upon both the time as well as temperature during the early period of gain in strength.

👉 The maturity of concrete is defined as the summation of product of time and temperature 

                                                 Maturity = ∑ (time x temperature)

👉 Its units are ℃ hr or ℃ days.

👉The temperature is reckoned from -11 ℃ as origin in the computation of maturity, since hydration continues to take place up to about this temperature.

👉 Example 1: A sample of concrete cured at 18℃ for 28 days is taken to be fully matured which is equal to ?

      Maturity (M28 days) = 28 x 24 x [ 18 - (-11)] = 19488 ℃ hr.

                                         OR

     Maturity (M28 days) = 28 x [ 18 - (-11)] = 1092 ℃ days.

👉 The relationship between maturity and strength of concrete is shown in figure below:

👉 The maturity concept is very useful for estimating the strength of concrete at any other maturity as a percentage of strength of concrete of known maturity by using the formula:

  Percentage of strength at maturity of 19800 ℃ hr = A + B log maturity/1000

👉Plowman has given the following values of constants A and B

     28 day strength at 18 ℃                                             Coefficients

   ( M = 19800 ℃ hr/kg/cm^2)                                       A              B

                < 175                                                              10             68

          175 - 350                                                              21             61

          350-525                                                                32             54

          525- 700                                                               42            46.5

Example 2: The strength of a fully matured concrete sample is found to be 500 kg/cm^2. Find the strength of identical concrete at age of 7 days when cured at an average temperature of 20 ℃ in day and 10 ℃ in night?

Solution: Maturity of concrete at the age of 7 days = ∑ (time x temperature)

                                     = 7 x 12 x [ 20 - (-11)] + [ 7 x 12 x (10-(-11)]

                                     = 4368 ℃ hr

 Now A = 32 , B = 54

Percentage of strength of concrete at maturity of 4368 ℃ hr = A + B log (4368/1000) 

                                                                                                = 32 + 54 x log (4368/1000)

                                                                                                 = 66.5%

Strength at 7 days = 500 x (66.5/100) = 332.5 kg/cm^2