## 1 Introduction
To date, there are nearly no studies that analyse the thermal behaviour of concrete with recycled cement from CDW. Only [PERSON] et al. [9] studied the thermal properties of high-performance concrete with ceramic powders, having analysed the thermal conductivity and specific heat capacity. According to the authors, thermal conductivity decreased from 1.69 Wm\({}^{-1}\).K\({}^{-1}\) (reference concrete) to 1.41 Wm\({}^{-1}\).K\({}^{-1}\) (concrete with 60% ceramic powder), due to an increase in open porosity from 11.2% to 15.5%. Additionally, with the replacement of cement, the specific heat capacity increased by about 13%. Several studies have been published on the thermal performance of concrete containing RA processed from CDW. [PERSON] et al. [12] evaluated the thermal behaviour of concrete with RA from CDW. The authors produced mixes with 0%, 10%, 25%, 50% and 100% of RA from four different recycling plants where for two mixes the authors only studied coarse RA and two mixes with only fine RA. It should be noted that all mixes were produced with the same workability (100 mm to 150 mm). The authors concluded that the total replacement of fine and coarse aggregates decreased thermal conductivity, respectively, between 22% and 42% and between 17% and 23%. The lower thermal conductivity of concrete with RA was explained by the lower density and thermal conductivity and the higher porosity of these aggregates. Hence, the authors concluded that the effect of using RA is quite variable depending on their nature. Despite this variation, several other investigations [13; 14; 15; 16; 17] also point to decreases in thermal conductivity higher than 20% in mixes with the replacement of natural aggregates with RA from concrete or glass. This work aims at analysing the thermal behaviour of concrete with recycled concrete powder, as partial cement replacement and RA from CDW, in order to fill the complete lack of information in the literature on this subject. This study started with the collection of CDW from a recycling plant, to be used as RA, and with the production of concrete powder, to be used instead of cement as a binder. In order to carry out this investigation, concrete was produced with RA from CDW (0% and 50%) and recycled cement with recycled concrete powder (0%, 10% and 25%) mixed with Portland cement. The analysis of the thermal behaviour of concrete was carried out through thermal conductivity and specific heat capacity tests, as well as by confronting these properties with the air content, the compressive strength, the open porosity and the electrical resistivity of these mixes. The joint analysis of these concrete properties and the physical and chemical properties of recycled concrete powder allowed a detailed analysis and understanding of the thermal performance of these mixes. The main innovation of this investigation is the analysis of the thermal behaviour of concrete with recycled concrete powder as partial cement replacement, which, as mentioned above, is totally innovative. Furthermore, the present study also evaluates the thermal behaviour of concrete that simultaneously contains recycled cement and recycled aggregates from CDW.