According to a recent OECD study, the global needs for infrastructure investment amount to 40,000€ billion by 2040. Faced with the scarcity of public funds, the financing of these needs is seen as a burden or a challenge, at a time when austerity is required even if the term itself is still taboo. Yet, through the existing legal and financial tools that are PPPs or concessions, the state has the capacity to use the private sector to ensure funding of projects to meet the fundamental changes in contemporary societies. But many obstacles remain for private investment, and especially the mobilization of capital over the long term. Infrastructure is requiring stable and sustainable investments. That is why the needs in economic and social development largely depend in the future, on the ability of states to shift long-term savings and to rely on specialized actors to fill the « infrastructure gap ».