Question

The strength of a fully matured concrete sample is $500kg/c{m}^2$. When cured at an average temperature of ${20}^{\circ }C$ in day, ${10}^{\circ }C$ in night, datum temperature $T_0$, is $-{11}^{\circ }C$. If Plowman constants $A$ is $32$ and $B$ is $54$, the strength of identical concrete at $7$ days will be nearly :

• A. $333kg/c{m}^2$
• B. $312kg/c{m}^2$
• C. $272kg/c{m}^2$
• D. $243kg/c{m}^2$

Answer 1

The correct option is A $333kg/c{m}^2$

Maturity of concrete at the age of $7\text{days}$
$M=\Sigma (\text{time}\times \text{temperature})$
$M=[20-(-11\left)\right]\times 12\times 7+[10-(-11\left)\right]\times 7\times 12$
$M=2604+1764$
$\begin{array}{c}M={4368}^{\circ }C-hr\end{array}$
$\text{\%}$ of strength of concrete of maturity of ${4368}^{\circ }Chr$
$f=A+Blo{g}_{10}(M\times {10}^{-3})$
$f=32+54lo{g}_{10}(4368\times {10}^{-3})$
$\begin{array}{c}f=66.57\text{\%}\end{array}$
Strength of concrete at $7\text{days}=0.6657\times 500$
$=332.85kg/c{m}^2$
$=333kg/c{m}^2$