# Experimental Evaluation of Thermal Performance and Durability of Thermally-Enhanced Concretes
## 4 Conclusions  
In order to increase the energy efficiency of residual sectors, this study presents the structural, thermal, and durability performances of thermally-enhanced concrete by applying various insulation materials. The use of various insulation materials resulted in the reduction of the density, compressive strength, and thermal properties (thermal conductivity and thermal transmission) by increasing the permeability and porosity of the concrete. This led to the rapid ingress of CO\({}_{2}\) resulting from accelerated carbonation experiments compared with normal concrete without insulation materials regardless of normalweight and lightweight coarse aggregates. From the experimental observations, the following conclusions were made:  
1. The effect of diatomic powder, hollow micro-spheres, and a micro-foam agent on thermal insulation and durability of concrete was proved. Diatomite powder failed to increase the strength due to its poor pozzolanic reaction than expected. In the case of the micro-foam agent, a higher cement content and a lower water-to-cement ratio should be applied to compensate for the strength.
2. For both normalweight aggregate concrete (NWAC) and lightweight aggregate concrete (LWAC), the concretes with the thermal insulating materials showed superior thermal insulation. The thermal conductivity measured from GHW was somewhat lower than that from QTM due to oven-drying the pore water and an increase in vacant pores.
3. The experimental results of compressive strength at 28 days and air-dry density show the close relationship with thermal conductivity and thermal transmission.
4. The reduction ratios of thermal transmission for all specimens were not large compared with the thermal conductivity from QTM and GHW. This is because CHB was related to the convection by the movement of heat flow or continuous circulation while, for QTM and GHW, the conduction was via directly physical contact.
5. Durability performance on carbonation and freeze-thaw attacks were experimentally examined. Firstly, carbonation rates of thermally-enhanced concretes using various insulation materials were higher than normal concretes regardless of aggregate types and mixtures due to the increased permeability and higher pores. Thus, additional methods to protect the concrete from carbonation, such as an increase in cover depth, is needed for thermally-enhanced concretes with various insulation materials.
6. Secondly, the addition of air-entraining agent and increased pores had a good influence on the resistance to freeze-thaw attack. This is because the test specimens had enough voids to absorb the volume expansion due to the freezing of the pore water.  
A test-bed house to prove the energy saving efficiency using these thermally-enhanced concretes was built in 2016 and has been monitored for more than a year. The monitored results can prove the efficiency of the thermally-enhanced concretes for our future works. In addition, to analyze the monitored energy consumption, virtual reality technology will be applied to emphasize the efficiency of the thermally-enhanced concretes to the public.  
This research was supported by a grant from the R and D Program of the Korea Railroad Research Institute, Republic of Korea.  
[PERSON] and [PERSON] designed and performed the tests. Also, they conceived the initial ideas. [PERSON] analyzed the data and wrote the paper. [PERSON] reviewed the results and the manuscript.  
The authors declare no conflict of interest.