Concrete sidewalks are always laid in sections, with gaps between each section.

Question

Concrete sidewalks are always laid in sections, with gaps between each section. For example, the drawing shows three identical 2.4-m sections, the outer two of which are against immovable walls. The two identical gaps between the sections are provided so that thermal expansion will not create the thermal stress that could lead to cracks. What is the minimum gap width necessary to account for an increase in temperature of 21 C

Concrete sidewalks are always laid in sections, with gaps between each section. For example, the drawing shows three identical 2.4-m sections, the outer two of which are against immovable walls. The two identical gaps between the sections are provided so that thermal expansion will not create the thermal stress that could lead to cracks. What is the minimum gap width necessary to account for an increase in temperature of 21 C degree ?

Explanation / Answer

thermal expansion for concrete is about 12E-6/C
(l-lo)/lo=a(T-To) where a is (linear) thermal expansion

(l-2.4)/2.4=12E-6(21)
l=2.4006048

this means the crack length needs to be 0.0006048m=0.6048mm

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