**9. Conclusions**

In this chapter, some of the most relevant research and main challenges concerning the production of low-carbon eco-efficient thermoactivated recycled cement were addressed. It is shown that recycled cement has a great potential for the efficient reuse of the large amount of waste concrete generated worldwide and the production for the very first time of fully recycled concrete, towards a truly circular economy. So far, recycled cement comparable to the low-grade Portland cement class 32.5 can be achieved and 28-day mortar compressive strengths over 20 MPa may be easily obtained, even considering their high w/b ratios. The main challenges that must be overcome are the high-water demand and non-standard setting times of RC. However, these issues are less relevant if RC is used as supplementary material for up to 40% replacement. In addition, other issues related to the optimization of the thermal activation process, effective separation of concrete constituents, and a deeper understanding of the dehydration and hydration process, as well as the physical, mechanical and durability behavior of recycled cement based materials need to be further addressed. However, although further research is needed, a significant step forward has been already achieved with the development of a more eco-efficient recycled binder able to respond to the very demanding environmental goals of the cement industry's road map. The aim is to supply the concrete industry with a very promising low-carbon binder, addressing the more efficient use of resources, the waste disposal issue and the decrease of the carbon footprint and associated quota.
