# Experimental Characterization of the Engineering Properties of Landfill Compost-Biocover
## 2 Materials and Methods
### Methods Employed
#### 2.2.5 Thermal Tests  
For thermal conductivity tests, each sample was prepared at a certain water content level and dry unit weight of the compaction curve, following the procedure discussed in Section 2.2.3. The compacted samples were taken out of the mold, wrapped in sealed polythene bags, and placed for at least two hours to attain thermal equilibrium before the test. A KD\({}_{2}\) Pro device was used to determine the thermal conductivity of the prepared specimens under isothermal conditions, which calculates values for thermal conductivity (K) by monitoring the dissipation of heat from a line heat source given a known voltage (KD\({}_{2}\) Pro Manual, 2006). The principle is based on the transient line heat conduction in a homogeneous, isotropic medium. The thermal conductivity is measured with a relative error of 5%. KD\({}_{2}\) analyzer allows a quick determination of the thermal conductivity compared to the differential scanning calorimeter (DSC), which requires a relatively long equilibrium time [37]. KD\({}_{2}\) Pro device consists of a TR1 sensor, consisting of a large single needle with 2.4 mm diameter and 100 mm length. The sensor needle was inserted into the compacted sample slowly and steadily, to avoid any chances of bend in the needle and reduce any chances of a gap between the needle and compost particles. It was assured that the sample surrounding the needle was more than 1.5 cm from all sides (KD\({}_{2}\) Pro Manual, 2006). The default reading time for the TR1 sensor is 5 min but a 10 min reading time was adjusted. The longer reading time provides more reliable results because it minimizes the chances of error, which occurs due to the large needle diameter and contact resistance between the sensor and compost materials. Replicate samples were prepared for each sample to obtain accurate test data.  
[PERSON] et al. [30] and [PERSON] [38] state that thermal diffusivity (\(\alpha\)) and heat capacity (Cp) are essential thermal properties that need to be addressed while examining the thermal behavior of compost materials. [PERSON] and [PERSON] [38] report a mathematical relationship as in Equation (2) to determine the specific heat of an organic medium.  
\[\text{Cp}=1.48-0.64\ (\text{Ash})+4.18\ (\text{M}\cdot\text{C}_{\text{d},\text{b}}) \tag{2}\]  
In Equation (2), Cp = specific heat of compost (kJ/kg\(\cdot\)K), M\(\cdot\text{C}_{\text{d},\text{b}}\) = moisture content of compost materials as per dry basis, and ash is the mineral content or ash of the material. Furthermore, [PERSON] et al. [30] report a relationship as in Equation (3) to estimate the thermal diffusivity in relation to specific heat and thermal conductivity of an organic  
Figure 3: Equilibrium condition for saturation of specimen at 71.85% water content and a dry density of 1075 kg/m\({}^{3}\).  
medium. In Equation (3); \(\alpha\) = thermal diffusivity (m\({}^{2}\)/s), \(\lambda\) = thermal conductivity (w/m\(\cdot\)K), \(\rho\) = bulk density (kg/m\({}^{3}\)), Cp = specific heat of material (kJ/kg\(\cdot\)K):  
\[\alpha=\lambda/(\rho\text{-Cp}). \tag{3}\]