The Resistive Plate Chamber (RPC) detectors in the CMS experiment operate with a gas mixture made of 95.2\% C$_2$H$_2$F$_4$, known to be a greenhouse gas. Several eco-friendly alternatives to C$_2$H$_2$F$_4$, such as HFO, have been studied in the last few years in order to find an alternative mixture with low Global-Warming Potential (GWP), while maintaining the performance of the RPC chambers. Another way to improve the RPC standard gas mixture GWP could be replacing between 30\% and 40\% of the C$_2$H$_2$F$_4$ with CO$_2$. Studies of eco-gas and CO$_2$ based mixtures are carried out at the CERN Gamma Irradiation Facility (GIF++), where the LHC Phase-2 conditions are mimicked by a 11.5 TBq radiation source and a muon beam. This study presents the performance of two 1.4 mm gap RPC chambers with several alternative gas mixtures in a high gamma background environment, as well as future perspectives of aging studies.