How Wide Should Expansion Cracks in Concrete Slabs Be to Prevent Buckling?

• The_Fritz
In summary, the appropriate width for the expansion cracks between the slabs in a concrete highway is at least 1.3 cm to prevent buckling, with a recommended width of 2-3 cm for added safety and stability. This calculation is based on the coefficient of linear expansion of concrete at different temperatures.
The_Fritz

Homework Statement

A concrete highway is built of slabs 14 m long (20 degrees Celsius)
How wide should the expansion cracks between the slabs be (at 15 deg Celsius) to prevent buckling if the range of temperature is - 30 deg Celsius to 48 deg C?

Homework Equations

$$\Delta$$L=$$\alpha$$L_0$$\Delta$$T

The Attempt at a Solution

Coefficient of Linear expansion ($$\alpha$$)for concrete at 20 deg C = 12*10^-6

$$\Delta$$L = (12*10^-6)(14m)(48-15 deg C) = .005544 m

$$\Delta$$L = (12*10^-6)(14m)(-30-15 deg C) = -.00756 m

Total range = .0055m + .0076m = .013m

To prevent buckling, the expansion cracks should be at least 1.3 cm wide. This will allow for enough expansion and contraction of the concrete without causing buckling. However, it is recommended to have a slightly wider expansion crack (around 2-3 cm) to account for any potential variations in temperature and to ensure the safety and stability of the highway.

To prevent buckling, the expansion cracks should be spaced at least .013m apart. However, it is recommended to add a safety factor of at least 10% to account for any unforeseen circumstances. Therefore, the expansion cracks between the slabs should be spaced at least .0143m (14.3 cm) apart to prevent buckling. It is important to also consider the type and thickness of the concrete, as well as the amount of traffic and weight on the highway, to ensure the safety and stability of the structure.

1. What is thermal expansion of concrete?

Thermal expansion of concrete refers to the tendency of concrete to expand or contract in response to changes in temperature. This is an important consideration in construction and can affect the durability and stability of concrete structures.

2. Why does concrete expand when exposed to high temperatures?

Concrete is made up of various materials, including cement, aggregates, and water. When heated, these materials expand at different rates, causing the concrete to expand as a whole. This expansion can also be caused by moisture within the concrete evaporating and creating pressure.

3. How does thermal expansion affect the strength of concrete?

Thermal expansion can cause stress and cracking in concrete structures, which can ultimately weaken the structure. In extreme cases, it can even lead to structural failure. Therefore, it is important to consider thermal expansion when designing and constructing concrete structures.

4. Can thermal expansion be prevented or controlled?

While thermal expansion cannot be completely prevented, it can be controlled to some extent. The use of expansion joints and proper reinforcement can help to minimize the effects of thermal expansion on concrete structures. In addition, using materials with lower coefficients of thermal expansion, such as certain types of cement, can also help to mitigate the effects of thermal expansion.

5. How is thermal expansion of concrete measured?

The coefficient of thermal expansion (CTE) is used to measure the amount of expansion or contraction that occurs in concrete in response to temperature changes. This is typically expressed in units of length per degree Celsius or Fahrenheit. The CTE can vary depending on the type and composition of the concrete, and it is important to consider this when designing and constructing concrete structures.

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