Pouring concrete is a difficult thing to do correctly. It must have the correct heat distribution to dry. This allows the water to bleed out at the correct rate and gives it the specified strength.

This was my job!

We wanted to look how pouring concrete in different season would effect how concrete dries. This had too many variable so we looked at how the temperature distribution in the pad was effected as the seasons changed. Looking at just the concrete slab wasn’t very interesting so we included the ground below it also to help understand how the heat is distributed.

A standard concrete slab is 4 inches thick. We will use 4 inches as our slab thickness, but it can be changed in the M-File. For our example we will assume that the concrete is in perfect contact with the ground and has 100% efficiency in transferring heat to the earth.

As can be seen here concrete isn’t homogeneous so a average “K” value will be used for ease of calculations

Yanal is hard at work on the code.

Many things had to be looked up like the thermal conductivity of concrete and dirt as well as the average temperature for the year and a function that describes the temperature change throughout the year.

This was Yanal’s job.

Using the heat equation were q from the earth is negligible and assuming that the wind is calm (v=0) so heat loss due to convection is neglected. The temperature was found to be 15˚ C by Countrystudies.us /united-states/weather. Heat fluctuation during the year follows a sinusoidal curve of T = 15 – 10sin(2πt/12 + 2). The offset is necessary to bring temperatures in accordance with local occurrences. This equation was empirically derived assuming steady increase and decrease of air temperature throughout the year for ease of calculation.

Plot adapted from SDSU.edu. This is only an example and was not Generated by our code.

Time (hours)

Distance (meters)

Tim

e (

hou

rs)

Distance (meters)

Dep

th (

mete

rs)

Figure 1: Shows the difference between the temperature at the surface of the floor and 5 meters below the surface.

Figure 2: Shows the average temperature for the year against the temperature fluctuation against time.

Figure 3: Shows the temperature change as the outside air temperature changes with the seasons. This graph is truncated at 5 meters deep.