# Experimental Evaluation of Thermal Performance and Durability of Thermally-Enhanced Concretes
## 2 Materials and Methods
### Test Methods
#### 2.2.1 Thermal Properties  
The measurement of thermal conductivity is always related to the detected heat flow and temperature difference. There are a number of methods to measure thermal conductivity and they have relatively large shortcomings depending on the raw materials, temperature range, and moisture conditions [24]. The measurement methods are classified as steady-state and transient techniques according to the energy or heat flux equilibrium conditions. The representative measurement methods using steady-state techniques are guarded hot plate (GHP) methods, such as ASTM C177 [15], whereas the typical transient methods are hot wire methods, i.e., ASTM C1113 [16]. The GHP method \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Label**} & \multirow{2}{*}{**Description**} & \multicolumn{2}{c}{**Volume Replacement Ratio of**} & \multirow{2}{*}{**Remark**} \\  & & & **Coarse Aggregate (\%)** & \\ \hline NN & Reference for NWAC [1] & - & None \\ LN & Reference for LWAC [2] & - & None \\ D & Diatomite powder & 15 \\ H & Hollow micro-sphere & 40 \\ M & Micro-foam agent & - & Chemical additive \\ \hline \hline \end{tabular}  
* \({}^{1}\) NWAC: Normalweight aggregate concrete; \({}^{2}\) LWAC: Lightweight aggregate concrete.  
\end{table} 
Table 4: Description of insulation materials. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Coarse Aggregate Type**} & \multirow{2}{*}{**Labels**} & \multirow{2}{*}{**W/C (\%)**} & \multicolumn{6}{c}{**Ingredients * (kg/m3)**} \\ \cline{3-10}  & & & **W** & **C** & **H** & **D** & **S** & **G** & **M** **\\ \hline \multirow{4}{*}{Normal (N)} & NN & 55.0 & 215 & 390 & - & - & 887 & 852 & - \\  & ND & 55.0 & 215 & 391 & - & 61 & 887 & 715 & - \\  & NH & 55.0 & 215 & 391 & 9 & - & 813 & 679 & - \\  & NM & 30.0 & 144 & 479 & - & - & 753 & 1059 & 19.2 \\ \hline \multirow{4}{*}{Light (L)} & LN & 55.0 & 215 & 390 & - & - & 802 & 543 & - \\  & LD & 55.0 & 215 & 391 & - & 61 & 802 & 393 & - \\  & LH & 55.0 & 215 & 391 & 9 & - & 813 & 366 & - \\  & LM & 30.0 & 144 & 479 & - & - & 753 & 575 & 19.2 \\ \hline \hline \end{tabular}  
* \({}^{*}\) W: water, C: cement; H: hollow micro-spheres; D: diatomic; M: micro-foam agent; S: sand (fine aggregate); G: gravel (crushed granite coarse aggregate).
* M: added as a chemical additive.  
\end{table} 
Table 5: Mixture designs of test specimens. is a widely used and versatile method, however, it can only obtain accurate results after reaching the moisture equilibrium. Meanwhile, hot wire methods employing transient techniques are commonly used and relatively rapid ways compared to guarded hot plate methods. Due to the irregular heat flux and heat loss between a hot wire and contact surface, it is known to indicate comparatively large experimental errors [24]. In spite of these disadvantages, there are diverse modified techniques based on the hot wire method. The well-known and well-established method is the probe method [17], utilizing a needle probe inserted into the specimen to determine the thermal properties of the lower conductivity in powder, soil, and concrete [27]. The quick thermal conductivity meter (QTM) with the probe, called the contact hot-wire method, was commercially developed to measure the temperature change, since this is very convenient and can expect relatively accurate results by repeating the test [9]. It is observed that all these methods result in a slight variation of thermal conductivity, especially in obviously heterogeneous material, such as concrete. [PERSON] et al. [7] proposed the linear heat flow method fitting temperature distribution curves and verified the reliability of this method to measure the thermal conductivity of concrete.