Question

The width of the expansion joint is 20 mm in a cement concrete pavement. The laying temperature is ${20}^{\circ }C$ and the maximum slab temperature in summer is ${60}^{\circ }C$. The coefficient of thermal expansion of concrete is $10\times {10}^{-6}mm/mm{/}^{\circ }C$ and the joint filler compressed upto 50% of the thickness. The spacing between expansion joints should be

• A. 30 m
• B. 20 m
• C. 25 m
• D. 40 m

Answer 1

The correct option is C 25 m

Width of expansion joint,
$=20mm$
Change in temperature,
$\Delta t={60}^{\circ }C-{20}^{\circ }C={40}^{\circ }C$
Coefficient of thermal expansion,
$\alpha =10\times {10}^{-6}{/}^{\circ }C={10}^{-5}{/}^{\circ }C$
Joint filler compresses upto 50%
$=\frac{20}{2}=10mm$
So, slab is allowed to expand
$\delta =20-10=10mm$
$\delta =L\alpha \Delta t$
$10\times {10}^{-3}=L\times {10}^{-5}\times 40$
$L=25m$